Geographic Variation in the Bioclimatic Niche, Hibernation, and Body Size of Anatolian Ground Squirrels

Geographic Variation in the Bioclimatic Niche, Hibernation, and Body Size of Anatolian Ground Squirrels | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Geographic Variation in the Bioclimatic Niche, Hibernation, and Body Size of Anatolian Ground Squirrels Mutlu Kart Gür, Tolga KANKILIÇ, Hakan GÜR This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6474074/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 19 Sep, 2025 Read the published version in Mammal Research → Version 1 posted 4 You are reading this latest preprint version Abstract Geographic variation in phenotypic traits offers key insights into how organisms adapt to diverse environmental conditions. In this study, we studied how elevational and associated environmental gradients shape geographic variation in the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels ( Spermophilus xanthoprymnus ). Specifically, we used presence data (170 out of 538 present records) from across the species’ range, body temperature data from 51 free-living individuals in two natural populations located 880 km apart, and body size data from 167 individuals across 10 populations to explore geographic variation in bioclimatic niche, hibernation, and body size across elevational and associated environmental gradients. Our results revealed that the bioclimatic niches of two deeply divergent mitochondrial (mt)DNA lineages (i.e. the western and eastern lineages) are distinct. However, this pattern appears to result from the underlying bioclimatic differences between the regions the western and eastern lineages inhabit. Anatolian ground squirrels from the eastern population, which inhabits a higher-elevation, colder, wetter, and more seasonally variable environment, exhibit longer hibernation periods, spend a higher proportion of this period in torpor bouts, and achieve deeper reductions in body temperature than conspecifics from the western population. Adult males exhibit shorter hibernation periods and spend a smaller proportion of this period in torpor bouts than the other age-sex classes. Anatolian ground squirrels from the eastern lineage, which inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments, are morphologically larger than conspecifics from the western lineage, particularly among males. Overall, our results demonstrate that spatial and environmental gradients shape phenotypic variation in Anatolian ground squirrels through lineage-, population- and demographic-level responses. By integrating bioclimatic niche, hibernation, and body size, this study highlights the importance of combining multiple trait dimensions to improve our understanding of eco-evolutionary divergence in hibernating mammals. Anatolia ecological niche modelling environmental gradients phenotypic variation Spermophilus xanthoprymnus Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Anatolian ground squirrels, Spermophilus xanthoprymnus (Bennett, 1835), are group-living, diurnal, hibernating, and pre-dominantly herbivorous, burrowing ground-dwelling rodents (Kart Gür and Gür 2010 ). They hibernate individually in underground burrows from late summer to late spring, with exact timing varying depending on geographic location, age, and sex (Gür and Kart Gür 2005 ; Kart Gür et al. 2009 ; Kart Gür and Gür 2015 ). Anatolian ground squirrels inhabit steppes and alpine vegetation at elevations ranging from approximately 800 m to 2,900 m above sea level. They are nearly endemic to Türkiye, primarily found in central and eastern (especially northeastern) Anatolia, with minor range extensions into western Armenia and northwestern Iran (Kryštufek and Vohralík 2005 , 2012 ; Kart Gür and Gür 2010 r 2013, 2022). Phylogeographically, Anatolian ground squirrels are structured into two deeply divergent parapatric cytochrome b (cyt b) mitochondrial (mt)DNA lineages distributed along a west-east axis across central and eastern Anatolia, roughly divided by the Kızılırmak River (Fig. 1 ). These lineages consist of two and three sub-lineages in the western and eastern regions, respectively (Gündüz et al. 2007 ). Elevation increases from central to eastern Anatolia (Fig. 1 ), leading to substantial environmental variation (Gür 2016 ). Consequently, Anatolian ground squirrels experience highly diverse environmental conditions throughout their range and are expected to exhibit geographic variation in phenotypic traits in response to these environmental differences. For instance, they follow a Bergmannian size pattern, with body size increasing as environmental temperature decreases (Gür 2010 ). Spatial and environmental gradients provide valuable opportunities to study geographic variation in phenotypic traits. Populations of a species inhabiting distinct geographic and environmental spaces experience diverse environmental conditions that drive adaptive differentiation (Bergmann 1847 ; Darwin 1859 ; Mayr 1956 ; Gould and Johnston 1972 ; McNab 2002 ). Although substantial research has examined geographic variation in niche, hibernation, and body size of mammals across such gradients (Meiri and Dayan 2003 ; Dunbar and Brigham 2010 ; Mazel et al. 2017 ), these traits have rarely been studied in combination. To address this gap, in this study, we studied how elevational and associated environmental gradients extending along a west-east axis from central to eastern Anatolia shape geographic variation in the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels. Besides simultaneously studying bioclimatic niche, hibernation, and body size, this study’s significant contribution is examining a physiological trait (monitoring body temperature during hibernation) in two geographically distinct populations under completely natural conditions. Although marmotine squirrels have been extensively studied in the context of hibernation, to our knowledge, outside of North America, no species of marmotine squirrel has been examined in two separate populations under natural conditions. Specifically, we used presence data (170 out of 538 present records) from across the species range, body temperature data from 51 free-living individuals in two natural populations located 880 km apart, and body size data from 167 individuals across 10 populations experiencing highly diverse environmental conditions to explore geographic variation in bioclimatic niche, hibernation, and body size across elevational and associated environmental gradients. Methods Bioclimatic niche To explore geographic variation in the bioclimatic niche of Anatolian ground squirrels ( Spermophilus xanthoprymnus ), presence data (538 records; Fig. 1 ) spanning the period 1990s–2018 and covering the species’ range were obtained from the Monitoring Project for the Effects of Environmental Changes on Ground Squirrels. This project also collects presence records of ground squirrels in Anatolia, primarily through field studies conducted throughout the active season, especially in spring (for further details, see Gür 2022 ). To minimize the effects of spatial sampling biases (Boria et al. 2014 ), the presence records were spatially filtered by reducing multiple records into a single record within distances of 10 km, 15 km, and 20 km in areas of high, medium, and low environmental heterogeneity, respectively (for further details, see Brown et al. 2017 r 2022). This spatial filtering resulted in 170 records used for ecological niche modelling (Fig. 2 ). Bioclimatic data, originally at a spatial resolution of 30 arc-seconds, were downloaded from the CHELSA database for present (1979–2013) conditions (Karger et al. 2017a , b ) and subsequently resampled to a spatial resolution of 2.5 arc-minutes. These data include 19 bioclimatic variables derived from monthly temperature and mean precipitation values (for further details, see https://chelsa-climate.org/ ). Based on current knowledge about the ecology of ground squirrels and long-term niche modelling analyses conducted as part of the Monitoring Project for the Effects of Environmental Changes on Ground Squirrels (Gür 2010 , 2013 ; Kart Gür and Gür 2010 r and Kart Gür 2012 r et al. 2018 r 2022), a subset of eight bioclimatic variables was selected: annual mean temperature and precipitation (BIO1 and 12), temperature and precipitation seasonality (BIO4 and 15), and mean temperature and precipitation of the coldest and warmest quarters (BIO10, 11, 18, and 19). All selected variables were masked to include only Anatolia and its surrounding regions. This selection represents a hypothesis of the M area (Soberon and Peterson 2005), defining the study area as 25° to 46° E and 35° to 43° N (Gür 2013 ; Fig. 2 ). To model the bioclimatic niche of Anatolian ground squirrels, the software MaxEnt (Phillips et al. 2017 ) was used, as it requires presence-only data (Peterson et al. 2011 ), generally outperforms other modelling approaches (Elith et al. 2006 ) and, for this species, performed similarly well to a complex ensemble model (for further details, see Supplemental Box 1 in Gür 2022 ). The contributions of bioclimatic variables to the final model were determined using the jackknife test. To regulate model complexity, different models were tested using all combinations of the following feature classes [Linear (L), Linear and Quadratic (LQ), Hinge (H), Linear, Quadratic, and Hinge (LQH), and Linear, Quadratic, Hinge, and Product (LQHP)] and regularization multipliers (1 to 5 in increments of 1). These models were calibrated using spatial jackknifing (k = 3). The model with the highest AUC [area under the curve of a receiver operating characteristic (ROC) plot] was selected as the best-performing model. Once the optimal model parameters were identified, a final model was developed using all presence records together (for further details, see Brown et al. 2017 ). Model performance and significance were evaluated through a partial ROC analysis (Peterson et al. 2008 ), as implemented in the software NicheToolBox (Osorio-Olvera 2020). Additionally, the univariate response curves were examined to determine whether they were biologically logical. To examine divergence in the bioclimatic niche, first, the geographic distribution of Anatolian ground squirrels was divided into two parts (referred to hereafter as the western and eastern lineages) based on the known distributions (i.e. 72 localities in Gündüz et al. 2007 ) of two deeply divergent parapatric cyt b mtDNA lineages distributed along a west-east axis across central and eastern Anatolia (Fig. 1 ). This was done by dividing the study area using Voronoi polygons generated from input localities and then grouping each polygon according to lineage relationships (for further details, see Brown et al. 2017 ). Then, 170 records were assigned to the western and eastern lineages (78 and 92 records, respectively), also considering the location of the Kızılırmak River as a geographic reference (Fig. 1 ). The bioclimatic niche was also modelled separately for each lineage, following the methodology described above. Unless otherwise stated, all above-mentioned processes and analyses were conducted using the software SDMtoolbox (Brown et al. 2017 ) and the software ArcGIS. Two quantitative tests of niche overlap (the niche identity and background tests) were conducted (for further details, see Warren et al. 2008 , 2010 ). The background test provides deeper insight and allows testing for niche differences that cannot be explained by the underlying environmental differences between the regions populations (in this case, the western and eastern lineages) inhabit. For the background test, background samples were drawn from the region each lineage inhabits, defined by a 100 km radius around the presence records. Both tests were performed with 100 randomized pseudoreplicates, as implemented in the software ENMTools (Warren et al. 2010 ). Niche overlap was quantified using two similar metrics, I and Schoener’s D (Schoener 1968 ; Warren et al. 2008 ), which range from 0 (completely divergent niches) to 1 (identical niches). Since both metrics yielded similar results, the discussion primarily focused on the I metric. To estimate the extent of overlap between areas of high bioclimatic suitability (defined as suitability values of 0.5 or higher) for the western and eastern lineages, the range overlap test was also conducted, as implemented in the software ENMTools. In addition to ecological niche modelling, to visualize divergence in the bioclimatic niche between the western and eastern lineages, a principal components analysis (PCA) was performed on the correlation matrix, derived from the data for 170 records and eight bioclimatic variables, as well as elevation, using the software PAST (Hammer et al. 2001). Elevation data (Jarvis et al. 2008 ) were used to understand how elevation shapes environmental variation between the western and eastern lineages. A Mann-Whitney U test was performed to evaluate differences in these variables between the western and eastern lineages. Hibernation To explore geographic variation in the hibernation of Anatolian ground squirrels, body temperature (Tb) data were collected from 51 free-living individuals in two natural populations: one (23 individuals) from the western lineage (39.48 N, 32.85 E, 1200 m, Ankara province; previously studied by Kart Gür et al. 2009 and Kart Gür and Gür 2015 ) and another (28 individuals) from the eastern lineage (40.55 N, 43.10 E, 1770 m, Kars province; previously unstudied). These populations (referred to hereafter as the western and eastern populations) are located 880 km apart from each other (Fig. 2 ). Field studies were conducted during the summers of 2005–2007 for the western population and 2013–2014 for the eastern population. Anatolian ground squirrels were trapped using live traps (Tomahawk Live Trap Co., Tomahawk, WI, USA) at irregular intervals throughout the active season. At initial capture, each individual was permanently marked with numbered metal ear tags (National Band and Tag Co., Newport, KY, USA). At each capture, date, tag number, age, sex, body mass (± 5 g, Pesola spring scale; Pesola AG, Rebmattli, Baar, Switzerland), and reproductive status were recorded. Individuals were classified as juvenile if captured during the active season of their birth year and as adult after their first hibernation (Gür and Kart Gür 2005 ; Kart Gür and Gür 2010 ). Near the end of the active season, 37 individuals from the western population and 32 from the eastern population were surgically implanted with temperature data loggers: Thermochron iButtons (DS1922L, ∼3 g, range − 40 to 85 ◦ C, resolution 0.0625 or 0.5 ◦ C; Maxim Integrated Products, Inc., Sunnyvale, CA, USA) or StowAway Tidbits (customized temperature data logger, 8.7 g, range − 4 to 44 ◦ C, resolution 0.16 ◦ C; Onset Computer Corporation, Bourne, MA, USA). The data loggers were programmed to record Tb at intervals of 15 min (StowAway Tidbits) or 50 min (with a resolution of 0.5 ◦ C, Thermochron iButtons). At the beginning of the subsequent active season, these loggers were surgically removed from 23 surviving individuals in the western population and 30 individuals in the eastern population. Throughout the hibernation season, soil temperature (Tsoil) was monitored at 1 m depth (the expected hibernacula depth; Karabağ 1953 ; Kart Gür et al. 2009 ; Kart Gür and Gür 2015 ) using a temperature logger (DS1922L; for specifications, see above) Tb data of 51 Anatolian ground squirrels from the western and eastern populations were analyzed for hibernation parameters (for further details, see Table 2 ). These parameters were calculated using an Excel-based macro developed in-house. Hibernation was defined as the period extending from the initiation of the first multiday torpor bout to the termination of the last such bout, during which individuals remained continuously underground (Kart Gür et al. 2009 ; Ruf and Geiser 2014 ; Kart Gür and Gür 2015 ). Torpor bouts were defined as periods extending from the first point when Tb was 30 ◦ C, whereas interbout arousals were defined as periods extending from the first point when Tb was > 30 ◦ C to the first point when Tb was < 30 ◦ C (Young 1990 ; Michener 1992 ; Ruf and Arnold 2000 ; Zervanos and Salsbury 2003 ; Buck et al. 2008 ; Kart Gür et al. 2009 ; Lee et al. 2009 ; Healy et al. 2012 ; Kart Gür and Gür 2015 ). Multiday torpor bouts lasted longer than 24 hours, whereas short torpor bouts lasted less than 24 hours (Kart Gür et al. 2009 ; Ruf and Geiser 2014 ; Kart Gür and Gür 2015 ). Table 2 Summary of the hibernation patterns of Anatolian ground squirrels ( Spermophilus xanthoprymnus ) by population and age-sex class. Descriptive statistics were presented as mean ± SE and range. Parameter Population Age-sex classes F-statistics Adult males Adult females Juvenile males Juvenile females n Western 3 9 4 7 Eastern 8 6 7 7 Beginning of hibernation (date) Western 31 Aug ± 6.66 (22 Aug–13 Sep) 15 Aug ± 4.89 (04 Aug–18 Sep) 10 Sep ± 2.87 (03–17 Sep) 09 Sep ± 1.84 (02–16 Sep) Pop: F(1,43) = 123.72*** Age-sex: F(3,43) = 17.76*** Interaction: F(3,43) = 1.28 Eastern 4 Aug ± 2.71 (19 Jul–10 Aug) 27 Jul ± 2.31 (21 Jul–04 Aug) 9 Aug ± 0.51 (07–11 Aug) 11 Aug ± 1.16 (07–15 Aug) End of hibernation (date) Western 14 Feb ± 3.48 (08–20 Feb) 10 Mar ± 2.20 (02–22 Mar) 09 Mar ± 4.82 (02–23 Mar) 27 Mar ± 3.46 (16 Mar–09 Apr) Pop: F(1,43) = 83.25*** Age-sex: F(3,43) = 39.65*** Interaction: F(3,43) = 5.62** Eastern 10 Mar ± 0.80 (07–13 Mar) 27 Mar ± 2.43 (19 Mar–03 Apr) 7 Apr ± 1.75 (29 Mar–11 Apr) 03 Apr ± 3.62 (19 Mar–11 Apr) Spring body mass (g) Western 252 ± 12 (235–275) 182 ± 6 (145–205) 175 ± 12 (160–210) 156 ± 7 (130–190) Pop: F(1,43) = 1.62 Age-sex: F(3,43) = 64.11*** Interaction: F(3,43) = 2.23 Eastern 286 ± 7 (265–320) 190 ± 13 (165–245) 169 ± 4 (155–185) 151 ± 6 (135–175) Total duration of hibernation (days) Western 167.50 ± 3.68 (160.17–171.70) 207.17 ± 5.29 (168.58–222.57) 180.22 ± 6.31 (166.15–195.64) 198.87 ± 3.04 (185.00–209.14) Pop: F(1,43) = 245.45*** Age-sex: F(3,43) = 20.33*** Interaction: F(3,43) = 4.58* Eastern 218.16 ± 2.79 (211.46–234.21) 242.86 ± 3.10 (229.92–252.80) 241.04 ± 1.61 (233.14–244.96) 234.35 ± 2.81 (223.00–242.02) Mean duration of torpor bouts (days) a Western 6.33 ± 0.25 (5.83–6.59) 7.74 ± 0.17 (6.72–8.29) 8.64 ± 0.35 (7.96–9.50) 8.02 ± 0.33 (7.24–9.74) Pop: F(1,43) = 25.66*** Age-sex: F(3,43) = 10.62*** Interaction: F(3,43) = 3.14* Eastern 8.18 ± 0.19 (7.67–9.10) 8.51 ± 0.24 (7.91–9.40) 8.81 ± 0.13 (8.30–9.22) 8.83 ± 0.23 (8.03–9.56) Mean duration of interbout arousals (days) a Western 1.14 ± 0.05 (1.08–1.24) 0.92 ± 0.02 (0.86–0.99) 0.91 ± 0.06 (0.83–1.09) 0.77 ± 0.05 (0.67–1.05) Pop: F(1,43) = 59.28*** Age-sex: F(3,43) = 36.49*** Interaction: F(3,43) = 0.92 Eastern 0.94 ± 0.02 (0.82–0.99) 0.77 ± 0.02 (0.73–0.82) 0.71 ± 0.01 (0.66–0.75) 0.66 ± 0.01 (0.63–0.68) Duration of the longest torpor bout (days) Western 14.04 ± 1.39 (11.88–16.63) 17.59 ± 0.59 (14.91–20.21) 18.84 ± 0.33 (18.02–19.61) 18.07 ± 0.74 (16.33–22.04) Pop: F(1,43) = 68.54*** Age-sex: F(3,43) = 5.03** Interaction: F(3,43) = 2.41 Eastern 20.83 ± 0.88 (16.89–25.04) 21.27 ± 0.38 (19.68–22.27) 21.76 ± 0.50 (19.21–23.42) 21.56 ± 0.40 (20.46–23.16) Number of torpor bouts Western 22.67 ± 1.20 (21–25) 24.11 ± 0.72 (20–28) 19.00 ± 0.41 (18–20) 22.71 ± 0.81 (20–26) Pop: F(1,43) = 31.78*** Age-sex: F(3,43) = 5.95** Interaction: F(3,43) = 4.33* Eastern 23.88 ± 0.61 (22–27) 26.33 ± 0.80 (24–29) 25.43 ± 0.37 (24–27) 24.86 ± 0.63 (23–28) Total duration of torpor bouts (days) Western 142.90 ± 2.32 (138.33–145.87) 186.06 ± 4.96 (149.79–199.13) 164.04 ± 6.98 (147.68–180.54) 182.02 ± 3.37 (168.93–194.76) Pop: F(1,43) = 276.42*** Age-sex: F(3,43) = 27.37*** Interaction: F(3,43) = 4.34* Eastern 196.48 ± 2.30 (190.38–209.71) 223.39 ± 2.86 (210.79–231.68) 223.67 ± 1.50 (215.77–226.92) 218.59 ± 2.88 (207.25–226.01) Total duration of interbout arousals (days) Western 24.59 ± 1.38 (21.84–26.11) 21.12 ± 0.61 (18.78–23.44) 16.19 ± 0.77 (15.09–18.47) 16.86 ± 0.96 (12.74–21.07) Pop: F(1,43) = 4.57* Age-sex: F(3,43) = 34.80*** Interaction: F(3,43) = 2.31 Eastern 21.68 ± 0.75 (18.84–24.50) 19.47 ± 0.52 (17.42–21.12) 17.37 ± 0.33 (16.25–18.83) 15.76 ± 0.33 (14.88–17.14) Total duration of torpor bouts as % of hibernation Western 85.34 ± 0.52 (84.70–86.36) 89.79 ± 0.26 (88.85–90.99) 90.95 ± 0.74 (88.88–92.28) 91.50 ± 0.52 (89.21–93.86) Pop: F(1,43) = 108.76*** Age-sex: F(3,43) = 59.65*** Interaction: F(3,43) = 6.53** Eastern 90.07 ± 0.27 (89.06–91.09) 91.98 ± 0.19 (91.65–92.79) 92.79 ± 0.12 (92.28–93.24) 93.27 ± 0.17 (92.59–93.77) Lowest minimum steady-state Tb (°C) Western 7.10 ± 0.51 (6.59–8.11) 5.42 ± 0.42 (3.61–7.62) 4.63 ± 0.40 (3.67–5.54) 3.66 ± 0.58 (1.67–6.19) Pop: F(1,43) = 98.23*** Age-sex: F(3,43) = 5.40** Interaction: F(3,43) = 2.67 Eastern 1.69 ± 0.62 (-1.45–3.50) 1.62 ± 0.43 (0.51–3.22) 1.96 ± 0.37 (1.03–3.50) 0.96 ± 0.27 (0.04–2.01) a Based on mean value throughout hibernation for each individual. *P < 0.05.**P < 0.01.***P < 0.001. P values were obtained by two-way ANOVA, and are given after false discovery rate correction Variation in any hibernation parameter of interest between the western and eastern populations, as well as among age-sex classes, was evaluated using a two-way ANOVA (Sokal and Rohlf 1995 ), according to the following statistical design: Hibernation parameter = Intercept + Population + Age-Sex Class + Population * Age-Sex Class Body size To explore geographic variation in the body size of Anatolian ground squirrels, the skulls of 167 adults (89 females and 78 males) across 10 populations (Fig. 2 ), covering most of the species’ range, were used (for further details, see Gür 2010 ). Of these populations, four (52 adults, 32 females and 20 males) were from the western lineage and six (115 adults, 57 females and 58 males) from the eastern lineage. Body size (here referring to skull size) was estimated using geometric morphometric analysis, which was preferred over traditional morphometric analysis used in Gür ( 2010 ), as it allows for a more effective separation of size and shape components of form (Bookstein 1991 ; Dryden and Mardia 1998 ). Accordingly, first, 12 two-dimensional landmarks, assumed to be homologous among all individuals analyzed, were digitized on the right side of the ventral view of the skulls, using the software tpsDig (Rohlf 2010 ). Then, skull size was estimated by the centroid size of landmark configurations, superimposed by Procrustes analysis (Dryden and Mardia 1998 ), using the software MorphoJ (Klingenberg 2011 ). Variation in skull size due to digitizing error was very low when a subsample of individuals (i.e. 30 randomly selected skulls) was digitized again and therefore skull size was estimated twice for these individuals. Variation in body size between the western and eastern lineages, as well as among populations and between sexes, was evaluated using a generalized linear model (GLM; McCullagh and Nelder 1989 ) with a normal probability distribution and identity link function, according to the following statistical design: Body size = Intercept + Lineage + Sex + Lineage * Sex + Population(Lineage) + Population * Sex(Lineage) Results Bioclimatic niche The final models were developed using the optimal model parameters reported in Table 1 . Each model performed better than a random prediction (i.e. the distribution of AUC ratios was significantly higher than expected by chance, P < 0.001 for each model; Table 1 ). Table 1 The contributions of bioclimatic variables to the final ecological niche model and sample statistics for Anatolian ground squirrels ( Spermophilus xanthoprymnus ), and for the western and eastern lineages. Variables/Parameters Variable contributions (with only variable/without variable) Sample statistics, median (interquartile range) Anatolian ground squirrels Western lineage Eastern lineage Anatolian ground squirrels Western lineage Eastern lineage BIO1 (C)*** 0.4322 / 1.0707 0.6856 / 1.6727 0.6694 / 1.2991 10.2 (8.1–12.1) 12.1 (10.7–12.7) 8.4 (7.0-9.8) BIO4 (C)*** 0.4926 / 1.0597 0.6275 / 1.6583 0.5510 / 1.2953 8.2 (8.0-8.5) 8.1 (7.8–8.3) 8.3 (8.1–8.8) BIO10 (C)*** 0.3575 / 1.0714 0.4959 / 1.6731 0.5837 / 1.3066 21.6 (19.8–23.5) 23.4 (22.0-24.2) 20.2 (18.8–21.5) BIO11 (C)*** 0.4461 / 1.0710 0.8033 / 1.6539 0.7475 / 1.2671 -0.6 (-3.6-1.3) 1.3 (0.2-2.0) -3.3 (-4.5–1.1) BIO12 (mm)*** 0.6259 / 1.0157 0.8948 / 1.5532 0.5216 / 1.2486 397 (354–452) 365 (339–410) 430 (385–471) BIO15 (%)* 0.5945 / 1.0426 0.5883 / 1.6431 0.6165 / 1.2547 46 (40–49) 44 (39–48) 47 (42–51) BIO18 (mm) 0.4998 / 1.0388 0.6512 / 1.6546 0.4063 / 1.2433 28 (18–38) 26 (17–35) 28 (21–41) BIO19 (mm)* 0.4494 / 1.0625 0.5038 / 1.6058 0.5012 / 1.2715 116 (105–140) 120 (107–144) 113 (99–137) Altitude (m)*** 1290 (1033–1645) 1034 (959–1192) 1586 (1300–1784) AUC 0.891 0.944 0.921 Feature class L, Q, H, and P L, Q, and H L, Q, H, and P Regularization multiplier 1 1 1 * P < 0.05, *** P < 0.001. P values were obtained by Mann-Whitney U test, and are given after false discovery rate correction. Note that altitude was not used for ecological niche modelling. Bold shows the variables that contributed most to the final model. Areas of high bioclimatic suitability were predicted across central and eastern Anatolia, corresponding to the geographic distribution of Anatolian ground squirrels ( Spermophilus xanthoprymnus ). Within the species, high-suitability areas were primarily predicted for the western and eastern lineages in the western and eastern parts of the geographic distribution of Anatolian ground squirrels, respectively (Fig. 2 ). These lineage-specific suitability areas were almost completely nested within the species-level suitability areas (thus not shown as a separate figure), indicating a spatial concordance between the combined lineage ranges and the species’ range. The variables that contributed most to the final model and, consequently, had the greatest influence on the geographic distribution are annual mean precipitation (BIO12) for both Anatolian ground squirrels and the western lineage, and mean temperature of the coldest quarter (winter temperature, BIO11) and precipitation of the warmest quarters (summer precipitation, BIO18) for the eastern lineage (Table 1 ; please note that these variables were identified in the PCA as those separating the lineages, Fig. 3 ). The overlap between areas of high bioclimatic suitability for the western and eastern lineages was 17.5%, suggesting that the bioclimatic niches of these lineages are not identical. This suggestion was supported by the identity test ( I = 0.658, null distribution = 0.940–0.989, P 0.05 for the western lineage vs. the eastern background and 0.622–0.752, P > 0.05 for the eastern lineage vs. the western background). Indeed, the univariate response curves, PCA results, and sample statistics consistently indicated that the eastern lineage inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments than the western lineage (Table 1 and Fig. 3 ). Hibernation The PCA results revealed that the western and eastern populations, in which geographic variation in hibernation was examined, were largely differentiated along an environmental gradient (PC1) primarily defined by elevation, temperature variables, and annual precipitation (Fig. 3 ). The ANOVA results showed significant main effects of both population and age-sex class on all hibernation parameters, except for spring body mass, which showed no significant effect of population. The eastern population consistently entered hibernation earlier, emerged later, and consequently exhibited a longer hibernation period than the western population. Additionally, it underwent longer durations in torpor bouts and shorter durations in interbout arousals, spent a higher proportion of the hibernation period in torpor bouts, and achieved lower minimum body temperatures, closely aligned with the lower ambient (soil) temperatures. Despite not focusing in detail on age-sex differences, adult males differed markedly from the other age-sex classes across both populations. Specifically, adult males emerged earlier, exhibited shorter hibernation periods, underwent shorter durations in torpor bouts and longer durations in interbout arousals, spent a smaller proportion of the hibernation period in torpor bouts (Table 2 and Fig. 4 , showing only representative adults from both populations). However, significant interaction effects of population and age-sex class were detected for a subset of hibernation parameters (Table 2 ), indicating that the physiological responses of both populations to environmental conditions are not consistent across age-sex classes and that such demographic variation is specific to certain aspects of hibernation. Body size The PCA results revealed that the populations, for which geographic variation in body size was examined, were differentiated along two environmental gradients: the first (PC1) primarily defined by elevation, temperature variables, and annual precipitation, and the second (PC2) primarily by summer precipitation and seasonality variables (Fig. 3 ). The GLM results showed significant main effects of lineage (Wald χ 2 = 48.799, df = 1, P < 0.001), sex (Wald χ 2 = 172.043, df = 1, P < 0.001), and population nested within lineage (Wald χ 2 = 219.643, df = 8, P < 0.001), along with a significant interaction effect of lineage and sex (Wald χ 2 = 6.209, df = 1, P = 0.013), but no significant interaction effect of population and sex nested within lineage (Wald χ 2 = 7.502, df = 8, P = 0.484). Specifically, although both lineages exhibited similar degrees of geographic variation in body size across sexes, the eastern lineage was morphologically larger than the western lineage, particularly among males. Discussion This study adopts a novel approach by simultaneously examining the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels ( Spermophilus xanthoprymnus ), three key ecological, physiological, and morphological traits that have rarely been studied in combination. By integrating ecological niche modeling (estimating bioclimatic niche using presence data), physiological monitoring (recording Tb using implanted data loggers), and morphological analysis (estimating body size using geometric morphometrics) across multiple populations, this study provides a comprehensive understanding of how spatial and environmental gradients shape geographic variation in Anatolian ground squirrels. To our knowledge, this is the first study to combine these three trait dimensions using three distinct methodologies within a single framework for any hibernating mammal. The distribution ecology of Anatolian ground squirrels ( Spermophilus xanthoprymnus ) has previously been studied using ecological niche modelling (Gür 2013 , 2022 ). These previous studies demonstrated that climate is one of the main factors limiting the geographic distribution of Anatolian ground squirrels and therefore they represent an ideal study system for ecological niche modelling. In these previous studies, as well as in most other studies (Smith et al. 2019 ), niche models have typically been constructed at the species level, treating the species as a single, undifferentiated entity responding to environments. This approach overlooks whether present data represent a single evolutionary unit or a set of independent evolutionary units, each differing in its respective niche. Yet, as is evident, divergence in the bioclimatic niche within Anatolian ground squirrels has not been studied. This study fills this gap by examining divergence in the bioclimatic niches of two deeply divergent parapatric cyt b mtDNA lineages distributed along a west-east axis across central and eastern Anatolia. Our results indicate that the bioclimatic niches of these lineages are distinct. However, this pattern appears to result from the underlying bioclimatic differences between the regions the western and eastern lineages inhabit. Specifically, the eastern lineage inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments than the western lineage. These findings suggest that the western and eastern lineages utilize the available bioclimatic environments in their respective ranges without exhibiting niche conservatism or divergence. However, beyond methodological considerations (Warren et al. 2008 , 2010 ), interpreting these results relies on the assumption that cyt b mtDNA lineages accurately represent independent evolutionary units within Anatolian ground squirrels, reflecting biologically meaningful patterns of niche divergence. An important question from evolutionary and physiological perspectives is whether phenotypic differentiation can occur in the absence of niche divergence. Accordingly, in this study, we further studied geographic variation in the hibernation and body size of Anatolian ground squirrels. In Anatolian ground squirrels, daily rhythmicity of body temperature before and during hibernation has previously been studied in a single population under both natural and laboratory conditions (Kart Gür et al. 2009 ). Additionally, a detailed characterization of hibernation, particularly focusing on age and sex differences, has been reported for the same population under natural conditions (Kart Gür and Gür 2015 ). While these previous studies provided valuable insights into hibernation in a single population, they did not address geographic variation. Indeed, unlike North American marmotine squirrels (Lehmer and Biggins 2005 ; Zervanos et al. 2010 ; Sheriff et al. 2011 ), geographic variation in the hibernation of Old World ground squirrels (the genus Spermophilus sensu stricto, Helgen et al. 2009 ), including Anatolian ground squirrels, has not yet been studied under natural conditions due to the methodological challenges involved in collecting high-resolution body temperature data from free-living individuals, especially across multiple populations. This study fills this gap by examining differences in the hibernation of two natural populations located 880 km apart and therefore provides the first comparative analysis of geographic variation in hibernation for Old World ground squirrels under natural conditions. Our results indicate that Anatolian ground squirrels from the eastern population, which inhabits a higher-elevation, colder, wetter, and more seasonally variable environment, exhibit longer hibernation periods, spend a higher proportion of this period in torpor bouts, and achieve deeper reductions in body temperature than conspecifics from the western population. Additionally, adult males exhibit shorter hibernation periods and spend a smaller proportion of this period in torpor bouts than the other age-sex classes. Given that areas at higher elevations with colder and more seasonally variable environments typically experience harsher and longer winters with increased energy demands and prolonged periods of food scarcity, physiological strategies such as extended hibernation and greater reliance on deeper, longer-lasting torpor bouts likely enable marmotine squirrels inhabiting these environments to conserve energy more efficiently (as discussed further below). Geographic variation in the body size of Anatolian ground squirrels in relation to environmental variables has already been studied in detail. In a previous study, variation in body size was analyzed at the population and sex levels (Gür 2010 ). Thus, this study extends that study by examining how population- and sex-level variation is structured at the lineage level. By analyzing variation in body size at the lineage level, this study provides a complementary and more integrative perspective, particularly given that geographic variation in bioclimatic niche and hibernation, are also investigated at the lineage level. This integrative approach allows us to better understand the broader evolutionary and ecological context shaping phenotypic variation. Our results indicate that Anatolian ground squirrels from the eastern lineage, which inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments, are morphologically larger than conspecifics from the western lineage, particularly among males. Many species of marmotine squirrels hibernate for up to 8–9 months each year. They rely primarily on fat reserves as a source of energy during hibernation. Accordingly, overwinter survival is positively correlated with the amount of fat stored prior to hibernation (Marmota: Armitage 2003 ; Cynomys: Hoogland 2003 ; Spermophilus: Yensen & Sherman 2003 ). However, in fat-storing hibernating mammals, the maximum amount of fat that can be stored is typically constrained to 40–50% of body mass, due to morphological limitations and costs associated with fat storage. Consequently, fat storage capacity scales proportionally with body size (Humphries et al. 2003 , 2004 ). In colder and more seasonally variable regions, such as those the eastern lineage inhabits, where winter energy demands are higher and food scarcity persists for prolonged periods, individuals, particularly adult males (see below), are expected to exhibit greater winter starvation resistance. This, in turn, necessitates increased fat accumulation prior to hibernation, which requires a morphologically larger body. In other words, greater winter starvation resistance may favour large body size (Boyce 1978 ; Lindstedt and Boyce 1985 ; Millar and Hickling 1990 r 2010; Gür and Kart Gür 2012 ). A similar pattern is also observed within species across age-sex classes. Differences between adult males and the other age-sex classes (Young 1990 ; Michener 1992 r and Kart Gür 2005 ; Buck et al. 2008 ; Healy et al. 2012 ; Kart Gür and Gür 2015 ), such as exhibiting shorter hibernation periods and spending a smaller proportion of this period in torpor bouts, suggest that adult males follow a less energy-conserving strategy and exhibit greater winter starvation resistance (French 1982 , 1988 r 2010; Gür and Kart Gür 2012 ). This pattern is possibly linked to trade-offs between the energy-saving benefits of torpor bouts and the reproductive benefits gained by terminating hibernation earlier (Healy et al. 2012 ). Indeed, Anatolian ground squirrels, particularly males, from the eastern lineage are morphologically larger, consistent with the demands of their more energetically challenging environment. Taken together, while geographic variation in body size likely reflects adaptation to increased energetic demands in colder and more seasonally variable environments, demographic variation (differences between sexes) in body size is likely shaped, at least in part, by trade-offs between hibernation and reproduction, which further accentuate differences between females and males within these environments. Overall, our results demonstrate that spatial and environmental gradients shape phenotypic variation in Anatolian ground squirrels through lineage-, population- and demographic-level responses. By integrating bioclimatic niche, hibernation, and body size, this study highlights the importance of combining multiple trait dimensions to improve our understanding of eco-evolutionary divergence in hibernating mammals. Declarations Competing interests The authors declare that they have no competing interests. Funding Funds were provided by the Scientific and Technological Research Council of Türkiye (TUBITAK, Project No. TBAG-104T279) for the hibernation study in Ankara; by Kırşehir Ahi Evran University (Project No. FBA-11-26) for the hibernation study in Kars; and by Hacettepe University (Project No. 0302601013) for the body size study. The Monitoring Project for the Effects of Environmental Changes on Ground Squirrels was largely self-funded, with additional support from Kırşehir Ahi Evran University (Project Nos. PYO-FEN.4001.12.012 and PYO-FEN.4001.15.008). All studies were conducted with the permission of Republic of Turkey Ministry of Agriculture and Forestry, General Directorate of Nature Conservation and National Parks. Author Contributions The study was conceived by MKG and HG. Field studies were coordinated by HG, and performed by MKG, TK and HG. Data analysis was performed by MKG and HG. Funding acquisition and project management were performed by MKG and HG. The manuscript was written by MKG and HG. All authors read and approved the final manuscript. Acknowledgements The authors are grateful to the Güzey family for their logistical support, to Gökben Kankılıç for her assistance with laboratory work, and to Mehmet Ali Kırpık from Kafkas University for providing laboratory facilities during the hibernation study conducted in Kars. We would like to thank Refik Ayata for developing the Excel-based macro used in this study. We would also like to express their gratitude once again to everyone who contributed to different parts of this study. These individuals have been acknowledged in the respective publications. References Armitage KB (2003) Marmots: Marmota monax and allies. In: Feldhamer GA, Thompson BC, Chapman JA (eds) Wild Mammals of North America: Biology, Management, and Conservation. Johns Hopkins University, Baltimore, pp 188–210 Bergmann C (1847) Ueber die Verhältnisse der Wärmeökonomie der Thiere zu ihrer Grösse. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6474074","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":449531013,"identity":"87ea7fd5-f2c6-45c6-9af9-259b7a32bfa4","order_by":0,"name":"Mutlu Kart Gür","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYHACxgMMB6DMD0DMxk5QBzMDWAsPSPMMkBZmUrQw80AE8APdGfkHDvOcscu3519j9tnm1zZ5PmYGxg8fc3BrMbuRzHCY50ayZY/EG+PZuX23DduYGZglZ24jpOUDswGPxBlj5tye24xALWzMvIS11EO0WPbctidSy43DBjz8PcbMDD9uJxLWcuaxwcE5Z44b8NxgK2bsbbid3MbM2IzfL8cTHz54c6zagL3/8GaGH39u285vbz744SMeLQggkQCMyzYQi7GBGPVAwH8ASPwhUvEoGAWjYBSMKAAAhs5Rt/0wNo4AAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-6691-8469","institution":"Kirsehir Ahi Evran Universitesi","correspondingAuthor":true,"prefix":"","firstName":"Mutlu","middleName":"Kart","lastName":"Gür","suffix":""},{"id":449531014,"identity":"fa48ebaa-169b-4d57-9ae5-6f7906fbb2a5","order_by":1,"name":"Tolga KANKILIÇ","email":"","orcid":"","institution":"Aksaray Universitesi","correspondingAuthor":false,"prefix":"","firstName":"Tolga","middleName":"","lastName":"KANKILIÇ","suffix":""},{"id":449531015,"identity":"cba04fa4-ded5-44d7-a66b-9df28165ba40","order_by":2,"name":"Hakan GÜR","email":"","orcid":"","institution":"Kirsehir Ahi Evran Universitesi","correspondingAuthor":false,"prefix":"","firstName":"Hakan","middleName":"","lastName":"GÜR","suffix":""}],"badges":[],"createdAt":"2025-04-17 18:46:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6474074/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6474074/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s13364-025-00815-z","type":"published","date":"2025-09-19T15:56:55+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82164391,"identity":"0c9d6951-3c42-4025-8fc5-6c56bc3c760b","added_by":"auto","created_at":"2025-05-07 09:05:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":7132226,"visible":true,"origin":"","legend":"\u003cp\u003eThe geographic distributions Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e) (based on 538 presence records from the Monitoring Project for the Effects of Environmental Changes on Ground Squirrels, green circles), and of the western (blue circles) and eastern (red circles) lineages (based on the known distributions —72 localities in Gündüz et al. 2007—of two deeply divergent parapatric cyt b mtDNA lineages distributed along a west-east axis across central and eastern Anatolia). The visible area in maps is 25° to 46° E and 35° to 43° N.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6474074/v1/166ab7310102a7a0f970d8d0.png"},{"id":82164388,"identity":"0c31e995-9dee-45c7-b0d6-386464c26734","added_by":"auto","created_at":"2025-05-07 09:05:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":4561099,"visible":true,"origin":"","legend":"\u003cp\u003eAreas of high bioclimatic suitability (increasing from cool to warm colors) for the western (blue) and eastern (red) lineages of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e), along with the locations of populations studied for hibernation (open circles) and body size (stars). Blue circles indicate 78 presence records for the western lineage, and red circles indicate 92 presence records for the eastern lineage.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6474074/v1/d9e843f2b18f0a7d5f2ad3ed.png"},{"id":82166544,"identity":"e0e4ac31-60c0-46e9-be56-1523095d6c2d","added_by":"auto","created_at":"2025-05-07 09:13:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":555020,"visible":true,"origin":"","legend":"\u003cp\u003eEnvironmental spaces of the western (blue circles, 78 presence records) and eastern (red circles, 92 presence records) lineages of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e), along with the locations of populations studied for hibernation (stars) and body size (open squares). The 95% confidence ellipses are shown for the western (solid black ellipse) and eastern (solid blue ellipse) lineages, together with a biplot of eight bioclimatic variables and elevation.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-6474074/v1/61b347d6241c7720033d390c.png"},{"id":82164405,"identity":"ea1564e5-6789-44e3-97c1-5ee50b110628","added_by":"auto","created_at":"2025-05-07 09:05:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":14771635,"visible":true,"origin":"","legend":"\u003cp\u003eBody temperature records over time of four representative adult females and males from two populations (western and eastern) of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e) before, duration, and after hibernation under natural conditions. Blacklines indicate body temperature, and dashed lines indicate soil temperature.\u003c/p\u003e","description":"","filename":"Fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-6474074/v1/44e05f09f13767ef1cfd35b8.png"},{"id":91890050,"identity":"904d4714-53fb-4b6c-907b-fb7eddb5d318","added_by":"auto","created_at":"2025-09-22 16:03:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":18312868,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6474074/v1/d7bdcc3b-5b49-4319-8806-be58aa4b132d.pdf"}],"financialInterests":"","formattedTitle":"Geographic Variation in the Bioclimatic Niche, Hibernation, and Body Size of Anatolian Ground Squirrels","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAnatolian ground squirrels, \u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e (Bennett, 1835), are group-living, diurnal, hibernating, and pre-dominantly herbivorous, burrowing ground-dwelling rodents (Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). They hibernate individually in underground burrows from late summer to late spring, with exact timing varying depending on geographic location, age, and sex (G\u0026uuml;r and Kart G\u0026uuml;r \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Anatolian ground squirrels inhabit steppes and alpine vegetation at elevations ranging from approximately 800 m to 2,900 m above sea level. They are nearly endemic to T\u0026uuml;rkiye, primarily found in central and eastern (especially northeastern) Anatolia, with minor range extensions into western Armenia and northwestern Iran (Kryštufek and Vohral\u0026iacute;k \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003er 2013, 2022). Phylogeographically, Anatolian ground squirrels are structured into two deeply divergent parapatric cytochrome b (cyt b) mitochondrial (mt)DNA lineages distributed along a west-east axis across central and eastern Anatolia, roughly divided by the Kızılırmak River (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These lineages consist of two and three sub-lineages in the western and eastern regions, respectively (G\u0026uuml;nd\u0026uuml;z et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Elevation increases from central to eastern Anatolia (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), leading to substantial environmental variation (G\u0026uuml;r \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Consequently, Anatolian ground squirrels experience highly diverse environmental conditions throughout their range and are expected to exhibit geographic variation in phenotypic traits in response to these environmental differences. For instance, they follow a Bergmannian size pattern, with body size increasing as environmental temperature decreases (G\u0026uuml;r \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSpatial and environmental gradients provide valuable opportunities to study geographic variation in phenotypic traits. Populations of a species inhabiting distinct geographic and environmental spaces experience diverse environmental conditions that drive adaptive differentiation (Bergmann \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1847\u003c/span\u003e; Darwin \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1859\u003c/span\u003e; Mayr \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1956\u003c/span\u003e; Gould and Johnston \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1972\u003c/span\u003e; McNab \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Although substantial research has examined geographic variation in niche, hibernation, and body size of mammals across such gradients (Meiri and Dayan \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Dunbar and Brigham \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Mazel et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), these traits have rarely been studied in combination. To address this gap, in this study, we studied how elevational and associated environmental gradients extending along a west-east axis from central to eastern Anatolia shape geographic variation in the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels. Besides simultaneously studying bioclimatic niche, hibernation, and body size, this study\u0026rsquo;s significant contribution is examining a physiological trait (monitoring body temperature during hibernation) in two geographically distinct populations under completely natural conditions. Although marmotine squirrels have been extensively studied in the context of hibernation, to our knowledge, outside of North America, no species of marmotine squirrel has been examined in two separate populations under natural conditions. Specifically, we used presence data (170 out of 538 present records) from across the species range, body temperature data from 51 free-living individuals in two natural populations located 880 km apart, and body size data from 167 individuals across 10 populations experiencing highly diverse environmental conditions to explore geographic variation in bioclimatic niche, hibernation, and body size across elevational and associated environmental gradients.\u003c/p\u003e"},{"header":"Methods","content":"\n\u003ch3\u003eBioclimatic niche\u003c/h3\u003e\n\u003cp\u003eTo explore geographic variation in the bioclimatic niche of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e), presence data (538 records; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) spanning the period 1990s\u0026ndash;2018 and covering the species\u0026rsquo; range were obtained from the Monitoring Project for the Effects of Environmental Changes on Ground Squirrels. This project also collects presence records of ground squirrels in Anatolia, primarily through field studies conducted throughout the active season, especially in spring (for further details, see G\u0026uuml;r \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). To minimize the effects of spatial sampling biases (Boria et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), the presence records were spatially filtered by reducing multiple records into a single record within distances of 10 km, 15 km, and 20 km in areas of high, medium, and low environmental heterogeneity, respectively (for further details, see Brown et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003er 2022). This spatial filtering resulted in 170 records used for ecological niche modelling (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBioclimatic data, originally at a spatial resolution of 30 arc-seconds, were downloaded from the CHELSA database for present (1979\u0026ndash;2013) conditions (Karger et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003eb\u003c/span\u003e) and subsequently resampled to a spatial resolution of 2.5 arc-minutes. These data include 19 bioclimatic variables derived from monthly temperature and mean precipitation values (for further details, see \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://chelsa-climate.org/\u003c/span\u003e\u003cspan address=\"https://chelsa-climate.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). Based on current knowledge about the ecology of ground squirrels and long-term niche modelling analyses conducted as part of the Monitoring Project for the Effects of Environmental Changes on Ground Squirrels (G\u0026uuml;r \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003er and Kart G\u0026uuml;r \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003er et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2018\u003c/span\u003er 2022), a subset of eight bioclimatic variables was selected: annual mean temperature and precipitation (BIO1 and 12), temperature and precipitation seasonality (BIO4 and 15), and mean temperature and precipitation of the coldest and warmest quarters (BIO10, 11, 18, and 19). All selected variables were masked to include only Anatolia and its surrounding regions. This selection represents a hypothesis of the M area (Soberon and Peterson 2005), defining the study area as 25\u0026deg; to 46\u0026deg; E and 35\u0026deg; to 43\u0026deg; N (G\u0026uuml;r \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo model the bioclimatic niche of Anatolian ground squirrels, the software MaxEnt (Phillips et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) was used, as it requires presence-only data (Peterson et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), generally outperforms other modelling approaches (Elith et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) and, for this species, performed similarly well to a complex ensemble model (for further details, see Supplemental Box 1 in G\u0026uuml;r \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The contributions of bioclimatic variables to the final model were determined using the jackknife test. To regulate model complexity, different models were tested using all combinations of the following feature classes [Linear (L), Linear and Quadratic (LQ), Hinge (H), Linear, Quadratic, and Hinge (LQH), and Linear, Quadratic, Hinge, and Product (LQHP)] and regularization multipliers (1 to 5 in increments of 1). These models were calibrated using spatial jackknifing (k\u0026thinsp;=\u0026thinsp;3). The model with the highest AUC [area under the curve of a receiver operating characteristic (ROC) plot] was selected as the best-performing model. Once the optimal model parameters were identified, a final model was developed using all presence records together (for further details, see Brown et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Model performance and significance were evaluated through a partial ROC analysis (Peterson et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), as implemented in the software NicheToolBox (Osorio-Olvera 2020). Additionally, the univariate response curves were examined to determine whether they were biologically logical.\u003c/p\u003e \u003cp\u003eTo examine divergence in the bioclimatic niche, first, the geographic distribution of Anatolian ground squirrels was divided into two parts (referred to hereafter as the western and eastern lineages) based on the known distributions (i.e. 72 localities in G\u0026uuml;nd\u0026uuml;z et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) of two deeply divergent parapatric cyt b mtDNA lineages distributed along a west-east axis across central and eastern Anatolia (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This was done by dividing the study area using Voronoi polygons generated from input localities and then grouping each polygon according to lineage relationships (for further details, see Brown et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Then, 170 records were assigned to the western and eastern lineages (78 and 92 records, respectively), also considering the location of the Kızılırmak River as a geographic reference (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The bioclimatic niche was also modelled separately for each lineage, following the methodology described above. Unless otherwise stated, all above-mentioned processes and analyses were conducted using the software SDMtoolbox (Brown et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and the software ArcGIS.\u003c/p\u003e \u003cp\u003eTwo quantitative tests of niche overlap (the niche identity and background tests) were conducted (for further details, see Warren et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). The background test provides deeper insight and allows testing for niche differences that cannot be explained by the underlying environmental differences between the regions populations (in this case, the western and eastern lineages) inhabit. For the background test, background samples were drawn from the region each lineage inhabits, defined by a 100 km radius around the presence records. Both tests were performed with 100 randomized pseudoreplicates, as implemented in the software ENMTools (Warren et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Niche overlap was quantified using two similar metrics, \u003cem\u003eI\u003c/em\u003e and Schoener\u0026rsquo;s \u003cem\u003eD\u003c/em\u003e (Schoener \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e1968\u003c/span\u003e; Warren et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), which range from 0 (completely divergent niches) to 1 (identical niches). Since both metrics yielded similar results, the discussion primarily focused on the \u003cem\u003eI\u003c/em\u003e metric. To estimate the extent of overlap between areas of high bioclimatic suitability (defined as suitability values of 0.5 or higher) for the western and eastern lineages, the range overlap test was also conducted, as implemented in the software ENMTools.\u003c/p\u003e \u003cp\u003eIn addition to ecological niche modelling, to visualize divergence in the bioclimatic niche between the western and eastern lineages, a principal components analysis (PCA) was performed on the correlation matrix, derived from the data for 170 records and eight bioclimatic variables, as well as elevation, using the software PAST (Hammer et al. 2001). Elevation data (Jarvis et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) were used to understand how elevation shapes environmental variation between the western and eastern lineages. A Mann-Whitney U test was performed to evaluate differences in these variables between the western and eastern lineages.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eHibernation\u003c/h2\u003e \u003cp\u003eTo explore geographic variation in the hibernation of Anatolian ground squirrels, body temperature (Tb) data were collected from 51 free-living individuals in two natural populations: one (23 individuals) from the western lineage (39.48 N, 32.85 E, 1200 m, Ankara province; previously studied by Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e and Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and another (28 individuals) from the eastern lineage (40.55 N, 43.10 E, 1770 m, Kars province; previously unstudied). These populations (referred to hereafter as the western and eastern populations) are located 880 km apart from each other (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eField studies were conducted during the summers of 2005\u0026ndash;2007 for the western population and 2013\u0026ndash;2014 for the eastern population. Anatolian ground squirrels were trapped using live traps (Tomahawk Live Trap Co., Tomahawk, WI, USA) at irregular intervals throughout the active season. At initial capture, each individual was permanently marked with numbered metal ear tags (National Band and Tag Co., Newport, KY, USA). At each capture, date, tag number, age, sex, body mass (\u0026plusmn;\u0026thinsp;5 g, Pesola spring scale; Pesola AG, Rebmattli, Baar, Switzerland), and reproductive status were recorded. Individuals were classified as juvenile if captured during the active season of their birth year and as adult after their first hibernation (G\u0026uuml;r and Kart G\u0026uuml;r \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Near the end of the active season, 37 individuals from the western population and 32 from the eastern population were surgically implanted with temperature data loggers: Thermochron iButtons (DS1922L, \u0026sim;3 g, range \u0026minus;\u0026thinsp;40 to 85 \u003csup\u003e◦\u003c/sup\u003eC, resolution 0.0625 or 0.5 \u003csup\u003e◦\u003c/sup\u003eC; Maxim Integrated Products, Inc., Sunnyvale, CA, USA) or StowAway Tidbits (customized temperature data logger, 8.7 g, range \u0026minus;\u0026thinsp;4 to 44 \u003csup\u003e◦\u003c/sup\u003eC, resolution 0.16 \u003csup\u003e◦\u003c/sup\u003eC; Onset Computer Corporation, Bourne, MA, USA). The data loggers were programmed to record Tb at intervals of 15 min (StowAway Tidbits) or 50 min (with a resolution of 0.5 \u003csup\u003e◦\u003c/sup\u003eC, Thermochron iButtons). At the beginning of the subsequent active season, these loggers were surgically removed from 23 surviving individuals in the western population and 30 individuals in the eastern population. Throughout the hibernation season, soil temperature (Tsoil) was monitored at 1 m depth (the expected hibernacula depth; Karabağ \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1953\u003c/span\u003e; Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) using a temperature logger (DS1922L; for specifications, see above)\u003c/p\u003e \u003cp\u003eTb data of 51 Anatolian ground squirrels from the western and eastern populations were analyzed for hibernation parameters (for further details, see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These parameters were calculated using an Excel-based macro developed in-house. Hibernation was defined as the period extending from the initiation of the first multiday torpor bout to the termination of the last such bout, during which individuals remained continuously underground (Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Ruf and Geiser \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Torpor bouts were defined as periods extending from the first point when Tb was \u0026lt;\u0026thinsp;30 \u003csup\u003e◦\u003c/sup\u003eC to the first point when Tb was \u0026gt;\u0026thinsp;30 \u003csup\u003e◦\u003c/sup\u003eC, whereas interbout arousals were defined as periods extending from the first point when Tb was \u0026gt;\u0026thinsp;30 \u003csup\u003e◦\u003c/sup\u003eC to the first point when Tb was \u0026lt;\u0026thinsp;30 \u003csup\u003e◦\u003c/sup\u003eC (Young \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Michener \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Ruf and Arnold \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Zervanos and Salsbury \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Buck et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Lee et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Healy et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Multiday torpor bouts lasted longer than 24 hours, whereas short torpor bouts lasted less than 24 hours (Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Ruf and Geiser \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of the hibernation patterns of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e) by population and age-sex class. Descriptive statistics were presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE and range.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePopulation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e \u003cp\u003eAge-sex classes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eF-statistics\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAdult males\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAdult females\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eJuvenile males\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJuvenile females\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eBeginning of hibernation (date)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31 Aug\u0026thinsp;\u0026plusmn;\u0026thinsp;6.66 (22 Aug\u0026ndash;13 Sep)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15 Aug\u0026thinsp;\u0026plusmn;\u0026thinsp;4.89 (04 Aug\u0026ndash;18 Sep)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10 Sep\u0026thinsp;\u0026plusmn;\u0026thinsp;2.87 (03\u0026ndash;17 Sep)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e09 Sep\u0026thinsp;\u0026plusmn;\u0026thinsp;1.84 (02\u0026ndash;16 Sep)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;123.72***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;17.76***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;1.28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 Aug\u0026thinsp;\u0026plusmn;\u0026thinsp;2.71 (19 Jul\u0026ndash;10 Aug)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27 Jul\u0026thinsp;\u0026plusmn;\u0026thinsp;2.31 (21 Jul\u0026ndash;04 Aug)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9 Aug\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51 (07\u0026ndash;11 Aug)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11 Aug\u0026thinsp;\u0026plusmn;\u0026thinsp;1.16 (07\u0026ndash;15 Aug)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eEnd of hibernation (date)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 Feb\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48 (08\u0026ndash;20 Feb)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10 Mar\u0026thinsp;\u0026plusmn;\u0026thinsp;2.20 (02\u0026ndash;22 Mar)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e09 Mar\u0026thinsp;\u0026plusmn;\u0026thinsp;4.82 (02\u0026ndash;23 Mar)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e27 Mar\u0026thinsp;\u0026plusmn;\u0026thinsp;3.46 (16 Mar\u0026ndash;09 Apr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;83.25***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;39.65***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;5.62**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 Mar\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80 (07\u0026ndash;13 Mar)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27 Mar\u0026thinsp;\u0026plusmn;\u0026thinsp;2.43 (19 Mar\u0026ndash;03 Apr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7 Apr\u0026thinsp;\u0026plusmn;\u0026thinsp;1.75 (29 Mar\u0026ndash;11 Apr)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e03 Apr\u0026thinsp;\u0026plusmn;\u0026thinsp;3.62 (19 Mar\u0026ndash;11 Apr)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSpring body mass (g)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e252\u0026thinsp;\u0026plusmn;\u0026thinsp;12 (235\u0026ndash;275)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e182\u0026thinsp;\u0026plusmn;\u0026thinsp;6 (145\u0026ndash;205)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e175\u0026thinsp;\u0026plusmn;\u0026thinsp;12 (160\u0026ndash;210)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e156\u0026thinsp;\u0026plusmn;\u0026thinsp;7 (130\u0026ndash;190)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;1.62\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;64.11***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;2.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e286\u0026thinsp;\u0026plusmn;\u0026thinsp;7 (265\u0026ndash;320)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e190\u0026thinsp;\u0026plusmn;\u0026thinsp;13 (165\u0026ndash;245)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e169\u0026thinsp;\u0026plusmn;\u0026thinsp;4 (155\u0026ndash;185)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e151\u0026thinsp;\u0026plusmn;\u0026thinsp;6 (135\u0026ndash;175)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal duration of hibernation (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e167.50\u0026thinsp;\u0026plusmn;\u0026thinsp;3.68 (160.17\u0026ndash;171.70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e207.17\u0026thinsp;\u0026plusmn;\u0026thinsp;5.29 (168.58\u0026ndash;222.57)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e180.22\u0026thinsp;\u0026plusmn;\u0026thinsp;6.31 (166.15\u0026ndash;195.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e198.87\u0026thinsp;\u0026plusmn;\u0026thinsp;3.04 (185.00\u0026ndash;209.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;245.45***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;20.33***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;4.58*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e218.16\u0026thinsp;\u0026plusmn;\u0026thinsp;2.79 (211.46\u0026ndash;234.21)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e242.86\u0026thinsp;\u0026plusmn;\u0026thinsp;3.10 (229.92\u0026ndash;252.80)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e241.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.61 (233.14\u0026ndash;244.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e234.35\u0026thinsp;\u0026plusmn;\u0026thinsp;2.81 (223.00\u0026ndash;242.02)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMean duration of torpor bouts (days)\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25 (5.83\u0026ndash;6.59)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17 (6.72\u0026ndash;8.29)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35 (7.96\u0026ndash;9.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33 (7.24\u0026ndash;9.74)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;25.66***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;10.62***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;3.14*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19 (7.67\u0026ndash;9.10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24 (7.91\u0026ndash;9.40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 (8.30\u0026ndash;9.22)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23 (8.03\u0026ndash;9.56)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMean duration of interbout arousals (days)\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 (1.08\u0026ndash;1.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 (0.86\u0026ndash;0.99)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 (0.83\u0026ndash;1.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 (0.67\u0026ndash;1.05)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;59.28***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;36.49***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;0.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 (0.82\u0026ndash;0.99)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 (0.73\u0026ndash;0.82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 (0.66\u0026ndash;0.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 (0.63\u0026ndash;0.68)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDuration of the longest torpor bout (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.39 (11.88\u0026ndash;16.63)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.59 (14.91\u0026ndash;20.21)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33 (18.02\u0026ndash;19.61)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e18.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74 (16.33\u0026ndash;22.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;68.54***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;5.03**\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;2.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88 (16.89\u0026ndash;25.04)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38 (19.68\u0026ndash;22.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50 (19.21\u0026ndash;23.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e21.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 (20.46\u0026ndash;23.16)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNumber of torpor bouts\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20 (21\u0026ndash;25)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72 (20\u0026ndash;28)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.41 (18\u0026ndash;20)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.71\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81 (20\u0026ndash;26)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;31.78***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;5.95**\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;4.33*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61 (22\u0026ndash;27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80 (24\u0026ndash;29)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37 (24\u0026ndash;27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e24.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.63 (23\u0026ndash;28)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal duration of torpor bouts (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e142.90\u0026thinsp;\u0026plusmn;\u0026thinsp;2.32 (138.33\u0026ndash;145.87)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e186.06\u0026thinsp;\u0026plusmn;\u0026thinsp;4.96 (149.79\u0026ndash;199.13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e164.04\u0026thinsp;\u0026plusmn;\u0026thinsp;6.98 (147.68\u0026ndash;180.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e182.02\u0026thinsp;\u0026plusmn;\u0026thinsp;3.37 (168.93\u0026ndash;194.76)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;276.42***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;27.37***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;4.34*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e196.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.30 (190.38\u0026ndash;209.71)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e223.39\u0026thinsp;\u0026plusmn;\u0026thinsp;2.86 (210.79\u0026ndash;231.68)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e223.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.50 (215.77\u0026ndash;226.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e218.59\u0026thinsp;\u0026plusmn;\u0026thinsp;2.88 (207.25\u0026ndash;226.01)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal duration of interbout arousals (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.38 (21.84\u0026ndash;26.11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61 (18.78\u0026ndash;23.44)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.77 (15.09\u0026ndash;18.47)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e16.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96 (12.74\u0026ndash;21.07)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;4.57*\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;34.80***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;2.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.68\u0026thinsp;\u0026plusmn;\u0026thinsp;0.75 (18.84\u0026ndash;24.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52 (17.42\u0026ndash;21.12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e17.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33 (16.25\u0026ndash;18.83)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33 (14.88\u0026ndash;17.14)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal duration of torpor bouts as % of hibernation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e85.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52 (84.70\u0026ndash;86.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e89.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26 (88.85\u0026ndash;90.99)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e90.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.74 (88.88\u0026ndash;92.28)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e91.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52 (89.21\u0026ndash;93.86)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;108.76***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;59.65***\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;6.53**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27 (89.06\u0026ndash;91.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e91.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19 (91.65\u0026ndash;92.79)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e92.79\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 (92.28\u0026ndash;93.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e93.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17 (92.59\u0026ndash;93.77)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLowest minimum steady-state Tb (\u0026deg;C)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWestern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51 (6.59\u0026ndash;8.11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 (3.61\u0026ndash;7.62)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 (3.67\u0026ndash;5.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.58 (1.67\u0026ndash;6.19)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePop: F(1,43)\u0026thinsp;=\u0026thinsp;98.23***\u003c/p\u003e \u003cp\u003eAge-sex: F(3,43)\u0026thinsp;=\u0026thinsp;5.40**\u003c/p\u003e \u003cp\u003eInteraction: F(3,43)\u0026thinsp;=\u0026thinsp;2.67\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEastern\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.62 (-1.45\u0026ndash;3.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43 (0.51\u0026ndash;3.22)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37 (1.03\u0026ndash;3.50)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.96 \u0026plusmn; 0.27 (0.04\u0026ndash;2.01)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003ea Based on mean value throughout hibernation for each individual. *P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.**P\u0026thinsp;\u0026lt;\u0026thinsp;0.01.***P\u0026thinsp;\u0026lt;\u0026thinsp;0.001. P values were obtained by two-way ANOVA, and are given after false discovery rate correction\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eVariation in any hibernation parameter of interest between the western and eastern populations, as well as among age-sex classes, was evaluated using a two-way ANOVA (Sokal and Rohlf \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1995\u003c/span\u003e), according to the following statistical design:\u003c/p\u003e \u003cp\u003eHibernation parameter\u0026thinsp;=\u0026thinsp;Intercept\u0026thinsp;+\u0026thinsp;Population\u0026thinsp;+\u0026thinsp;Age-Sex Class\u0026thinsp;+\u0026thinsp;Population * Age-Sex Class\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eBody size\u003c/h3\u003e\n\u003cp\u003eTo explore geographic variation in the body size of Anatolian ground squirrels, the skulls of 167 adults (89 females and 78 males) across 10 populations (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), covering most of the species\u0026rsquo; range, were used (for further details, see G\u0026uuml;r \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Of these populations, four (52 adults, 32 females and 20 males) were from the western lineage and six (115 adults, 57 females and 58 males) from the eastern lineage.\u003c/p\u003e \u003cp\u003eBody size (here referring to skull size) was estimated using geometric morphometric analysis, which was preferred over traditional morphometric analysis used in G\u0026uuml;r (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), as it allows for a more effective separation of size and shape components of form (Bookstein \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Dryden and Mardia \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Accordingly, first, 12 two-dimensional landmarks, assumed to be homologous among all individuals analyzed, were digitized on the right side of the ventral view of the skulls, using the software tpsDig (Rohlf \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Then, skull size was estimated by the centroid size of landmark configurations, superimposed by Procrustes analysis (Dryden and Mardia \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1998\u003c/span\u003e), using the software MorphoJ (Klingenberg \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Variation in skull size due to digitizing error was very low when a subsample of individuals (i.e. 30 randomly selected skulls) was digitized again and therefore skull size was estimated twice for these individuals.\u003c/p\u003e \u003cp\u003eVariation in body size between the western and eastern lineages, as well as among populations and between sexes, was evaluated using a generalized linear model (GLM; McCullagh and Nelder \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e1989\u003c/span\u003e) with a normal probability distribution and identity link function, according to the following statistical design:\u003c/p\u003e \u003cp\u003eBody size\u0026thinsp;=\u0026thinsp;Intercept\u0026thinsp;+\u0026thinsp;Lineage\u0026thinsp;+\u0026thinsp;Sex\u0026thinsp;+\u0026thinsp;Lineage * Sex\u0026thinsp;+\u0026thinsp;Population(Lineage)\u0026thinsp;+\u0026thinsp;Population * Sex(Lineage)\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eBioclimatic niche\u003c/h2\u003e \u003cp\u003eThe final models were developed using the optimal model parameters reported in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Each model performed better than a random prediction (i.e. the distribution of AUC ratios was significantly higher than expected by chance, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for each model; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe contributions of bioclimatic variables to the final ecological niche model and sample statistics for Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e), and for the western and eastern lineages.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVariables/Parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eVariable contributions (with only variable/without variable)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eSample statistics, median (interquartile range)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAnatolian ground squirrels\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWestern lineage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eEastern lineage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAnatolian ground squirrels\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eWestern lineage\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eEastern lineage\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO1 (C)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4322 / 1.0707\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6856 / 1.6727\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.6694 / 1.2991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.2 (8.1\u0026ndash;12.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12.1 (10.7\u0026ndash;12.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.4 (7.0-9.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO4 (C)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4926 / 1.0597\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6275 / 1.6583\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5510 / 1.2953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.2 (8.0-8.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.1 (7.8\u0026ndash;8.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.3 (8.1\u0026ndash;8.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO10 (C)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.3575 / 1.0714\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.4959 / 1.6731\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5837 / 1.3066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21.6 (19.8\u0026ndash;23.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e23.4 (22.0-24.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e20.2 (18.8\u0026ndash;21.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO11 (C)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4461 / 1.0710\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.8033 / 1.6539\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.7475\u003c/b\u003e / 1.2671\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.6 (-3.6-1.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.3 (0.2-2.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-3.3 (-4.5\u0026ndash;1.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO12 (mm)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.6259\u003c/b\u003e / \u003cb\u003e1.0157\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.8948\u003c/b\u003e / \u003cb\u003e1.5532\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5216 / 1.2486\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e397 (354\u0026ndash;452)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e365 (339\u0026ndash;410)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e430 (385\u0026ndash;471)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO15 (%)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.5945 / 1.0426\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5883 / 1.6431\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.6165 / 1.2547\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e46 (40\u0026ndash;49)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e44 (39\u0026ndash;48)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e47 (42\u0026ndash;51)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO18 (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4998 / 1.0388\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.6512 / 1.6546\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.4063 / \u003cb\u003e1.2433\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28 (18\u0026ndash;38)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26 (17\u0026ndash;35)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28 (21\u0026ndash;41)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBIO19 (mm)*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4494 / 1.0625\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.5038 / 1.6058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5012 / 1.2715\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e116 (105\u0026ndash;140)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e120 (107\u0026ndash;144)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e113 (99\u0026ndash;137)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAltitude (m)***\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1290 (1033\u0026ndash;1645)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1034 (959\u0026ndash;1192)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1586 (1300\u0026ndash;1784)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAUC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.891\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.944\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.921\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFeature class\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eL, Q, H, and P\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eL, Q, and H\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eL, Q, H, and P\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegularization multiplier\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e* P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, *** P\u0026thinsp;\u0026lt;\u0026thinsp;0.001. P values were obtained by Mann-Whitney U test, and are given after false discovery rate correction. Note that altitude was not used for ecological niche modelling. Bold shows the variables that contributed most to the final model.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAreas of high bioclimatic suitability were predicted across central and eastern Anatolia, corresponding to the geographic distribution of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e). Within the species, high-suitability areas were primarily predicted for the western and eastern lineages in the western and eastern parts of the geographic distribution of Anatolian ground squirrels, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). These lineage-specific suitability areas were almost completely nested within the species-level suitability areas (thus not shown as a separate figure), indicating a spatial concordance between the combined lineage ranges and the species\u0026rsquo; range. The variables that contributed most to the final model and, consequently, had the greatest influence on the geographic distribution are annual mean precipitation (BIO12) for both Anatolian ground squirrels and the western lineage, and mean temperature of the coldest quarter (winter temperature, BIO11) and precipitation of the warmest quarters (summer precipitation, BIO18) for the eastern lineage (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e; please note that these variables were identified in the PCA as those separating the lineages, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The overlap between areas of high bioclimatic suitability for the western and eastern lineages was 17.5%, suggesting that the bioclimatic niches of these lineages are not identical. This suggestion was supported by the identity test (\u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.658, null distribution\u0026thinsp;=\u0026thinsp;0.940\u0026ndash;0.989, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). However, the background test indicated that the bioclimatic niches and background areas are equally divergent (\u003cem\u003eI\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.658, null distribution\u0026thinsp;=\u0026thinsp;0.566\u0026ndash;0.711, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05 for the western lineage vs. the eastern background and 0.622\u0026ndash;0.752, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05 for the eastern lineage vs. the western background). Indeed, the univariate response curves, PCA results, and sample statistics consistently indicated that the eastern lineage inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments than the western lineage (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eHibernation\u003c/h3\u003e\n\u003cp\u003eThe PCA results revealed that the western and eastern populations, in which geographic variation in hibernation was examined, were largely differentiated along an environmental gradient (PC1) primarily defined by elevation, temperature variables, and annual precipitation (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The ANOVA results showed significant main effects of both population and age-sex class on all hibernation parameters, except for spring body mass, which showed no significant effect of population. The eastern population consistently entered hibernation earlier, emerged later, and consequently exhibited a longer hibernation period than the western population. Additionally, it underwent longer durations in torpor bouts and shorter durations in interbout arousals, spent a higher proportion of the hibernation period in torpor bouts, and achieved lower minimum body temperatures, closely aligned with the lower ambient (soil) temperatures. Despite not focusing in detail on age-sex differences, adult males differed markedly from the other age-sex classes across both populations. Specifically, adult males emerged earlier, exhibited shorter hibernation periods, underwent shorter durations in torpor bouts and longer durations in interbout arousals, spent a smaller proportion of the hibernation period in torpor bouts (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, showing only representative adults from both populations). However, significant interaction effects of population and age-sex class were detected for a subset of hibernation parameters (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e2\u003c/span\u003e), indicating that the physiological responses of both populations to environmental conditions are not consistent across age-sex classes and that such demographic variation is specific to certain aspects of hibernation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eBody size\u003c/h2\u003e \u003cp\u003eThe PCA results revealed that the populations, for which geographic variation in body size was examined, were differentiated along two environmental gradients: the first (PC1) primarily defined by elevation, temperature variables, and annual precipitation, and the second (PC2) primarily by summer precipitation and seasonality variables (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The GLM results showed significant main effects of lineage (Wald χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;48.799, df\u0026thinsp;=\u0026thinsp;1, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), sex (Wald χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;172.043, df\u0026thinsp;=\u0026thinsp;1, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and population nested within lineage (Wald χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;219.643, df\u0026thinsp;=\u0026thinsp;8, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), along with a significant interaction effect of lineage and sex (Wald χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;6.209, df\u0026thinsp;=\u0026thinsp;1, P\u0026thinsp;=\u0026thinsp;0.013), but no significant interaction effect of population and sex nested within lineage (Wald χ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;7.502, df\u0026thinsp;=\u0026thinsp;8, P\u0026thinsp;=\u0026thinsp;0.484). Specifically, although both lineages exhibited similar degrees of geographic variation in body size across sexes, the eastern lineage was morphologically larger than the western lineage, particularly among males.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study adopts a novel approach by simultaneously examining the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e), three key ecological, physiological, and morphological traits that have rarely been studied in combination. By integrating ecological niche modeling (estimating bioclimatic niche using presence data), physiological monitoring (recording Tb using implanted data loggers), and morphological analysis (estimating body size using geometric morphometrics) across multiple populations, this study provides a comprehensive understanding of how spatial and environmental gradients shape geographic variation in Anatolian ground squirrels. To our knowledge, this is the first study to combine these three trait dimensions using three distinct methodologies within a single framework for any hibernating mammal.\u003c/p\u003e \u003cp\u003eThe distribution ecology of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e) has previously been studied using ecological niche modelling (G\u0026uuml;r \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2013\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These previous studies demonstrated that climate is one of the main factors limiting the geographic distribution of Anatolian ground squirrels and therefore they represent an ideal study system for ecological niche modelling. In these previous studies, as well as in most other studies (Smith et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), niche models have typically been constructed at the species level, treating the species as a single, undifferentiated entity responding to environments. This approach overlooks whether present data represent a single evolutionary unit or a set of independent evolutionary units, each differing in its respective niche. Yet, as is evident, divergence in the bioclimatic niche within Anatolian ground squirrels has not been studied. This study fills this gap by examining divergence in the bioclimatic niches of two deeply divergent parapatric cyt b mtDNA lineages distributed along a west-east axis across central and eastern Anatolia. Our results indicate that the bioclimatic niches of these lineages are distinct. However, this pattern appears to result from the underlying bioclimatic differences between the regions the western and eastern lineages inhabit. Specifically, the eastern lineage inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments than the western lineage. These findings suggest that the western and eastern lineages utilize the available bioclimatic environments in their respective ranges without exhibiting niche conservatism or divergence. However, beyond methodological considerations (Warren et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), interpreting these results relies on the assumption that cyt b mtDNA lineages accurately represent independent evolutionary units within Anatolian ground squirrels, reflecting biologically meaningful patterns of niche divergence. An important question from evolutionary and physiological perspectives is whether phenotypic differentiation can occur in the absence of niche divergence. Accordingly, in this study, we further studied geographic variation in the hibernation and body size of Anatolian ground squirrels.\u003c/p\u003e \u003cp\u003eIn Anatolian ground squirrels, daily rhythmicity of body temperature before and during hibernation has previously been studied in a single population under both natural and laboratory conditions (Kart G\u0026uuml;r et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Additionally, a detailed characterization of hibernation, particularly focusing on age and sex differences, has been reported for the same population under natural conditions (Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). While these previous studies provided valuable insights into hibernation in a single population, they did not address geographic variation. Indeed, unlike North American marmotine squirrels (Lehmer and Biggins \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Zervanos et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Sheriff et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), geographic variation in the hibernation of Old World ground squirrels (the genus \u003cem\u003eSpermophilus\u003c/em\u003e sensu stricto, Helgen et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), including Anatolian ground squirrels, has not yet been studied under natural conditions due to the methodological challenges involved in collecting high-resolution body temperature data from free-living individuals, especially across multiple populations. This study fills this gap by examining differences in the hibernation of two natural populations located 880 km apart and therefore provides the first comparative analysis of geographic variation in hibernation for Old World ground squirrels under natural conditions. Our results indicate that Anatolian ground squirrels from the eastern population, which inhabits a higher-elevation, colder, wetter, and more seasonally variable environment, exhibit longer hibernation periods, spend a higher proportion of this period in torpor bouts, and achieve deeper reductions in body temperature than conspecifics from the western population. Additionally, adult males exhibit shorter hibernation periods and spend a smaller proportion of this period in torpor bouts than the other age-sex classes. Given that areas at higher elevations with colder and more seasonally variable environments typically experience harsher and longer winters with increased energy demands and prolonged periods of food scarcity, physiological strategies such as extended hibernation and greater reliance on deeper, longer-lasting torpor bouts likely enable marmotine squirrels inhabiting these environments to conserve energy more efficiently (as discussed further below).\u003c/p\u003e \u003cp\u003eGeographic variation in the body size of Anatolian ground squirrels in relation to environmental variables has already been studied in detail. In a previous study, variation in body size was analyzed at the population and sex levels (G\u0026uuml;r \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Thus, this study extends that study by examining how population- and sex-level variation is structured at the lineage level. By analyzing variation in body size at the lineage level, this study provides a complementary and more integrative perspective, particularly given that geographic variation in bioclimatic niche and hibernation, are also investigated at the lineage level. This integrative approach allows us to better understand the broader evolutionary and ecological context shaping phenotypic variation. Our results indicate that Anatolian ground squirrels from the eastern lineage, which inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments, are morphologically larger than conspecifics from the western lineage, particularly among males. Many species of marmotine squirrels hibernate for up to 8\u0026ndash;9 months each year. They rely primarily on fat reserves as a source of energy during hibernation. Accordingly, overwinter survival is positively correlated with the amount of fat stored prior to hibernation (Marmota: Armitage \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Cynomys: Hoogland \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Spermophilus: Yensen \u0026amp; Sherman \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). However, in fat-storing hibernating mammals, the maximum amount of fat that can be stored is typically constrained to 40\u0026ndash;50% of body mass, due to morphological limitations and costs associated with fat storage. Consequently, fat storage capacity scales proportionally with body size (Humphries et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). In colder and more seasonally variable regions, such as those the eastern lineage inhabits, where winter energy demands are higher and food scarcity persists for prolonged periods, individuals, particularly adult males (see below), are expected to exhibit greater winter starvation resistance. This, in turn, necessitates increased fat accumulation prior to hibernation, which requires a morphologically larger body. In other words, greater winter starvation resistance may favour large body size (Boyce \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Lindstedt and Boyce \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Millar and Hickling \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1990\u003c/span\u003er 2010; G\u0026uuml;r and Kart G\u0026uuml;r \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). A similar pattern is also observed within species across age-sex classes. Differences between adult males and the other age-sex classes (Young \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Michener \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1992\u003c/span\u003er and Kart G\u0026uuml;r \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Buck et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Healy et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Kart G\u0026uuml;r and G\u0026uuml;r \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), such as exhibiting shorter hibernation periods and spending a smaller proportion of this period in torpor bouts, suggest that adult males follow a less energy-conserving strategy and exhibit greater winter starvation resistance (French \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1982\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1988\u003c/span\u003er 2010; G\u0026uuml;r and Kart G\u0026uuml;r \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). This pattern is possibly linked to trade-offs between the energy-saving benefits of torpor bouts and the reproductive benefits gained by terminating hibernation earlier (Healy et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Indeed, Anatolian ground squirrels, particularly males, from the eastern lineage are morphologically larger, consistent with the demands of their more energetically challenging environment. Taken together, while geographic variation in body size likely reflects adaptation to increased energetic demands in colder and more seasonally variable environments, demographic variation (differences between sexes) in body size is likely shaped, at least in part, by trade-offs between hibernation and reproduction, which further accentuate differences between females and males within these environments.\u003c/p\u003e \u003cp\u003eOverall, our results demonstrate that spatial and environmental gradients shape phenotypic variation in Anatolian ground squirrels through lineage-, population- and demographic-level responses. By integrating bioclimatic niche, hibernation, and body size, this study highlights the importance of combining multiple trait dimensions to improve our understanding of eco-evolutionary divergence in hibernating mammals.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eFunds were provided by the Scientific and Technological Research Council of T\u0026uuml;rkiye (TUBITAK, Project No. TBAG-104T279) for the hibernation study in Ankara; by Kırşehir Ahi Evran University (Project No. FBA-11-26) for the hibernation study in Kars; and by Hacettepe University (Project No. 0302601013) for the body size study. The Monitoring Project for the Effects of Environmental Changes on Ground Squirrels was largely self-funded, with additional support from Kırşehir Ahi Evran University (Project Nos. PYO-FEN.4001.12.012 and PYO-FEN.4001.15.008). All studies were conducted with the permission of Republic of Turkey Ministry of Agriculture and Forestry, General Directorate of Nature Conservation and National Parks.\u003c/p\u003e\u003ch2\u003eAuthor Contributions\u003c/h2\u003e \u003cp\u003eThe study was conceived by MKG and HG. Field studies were coordinated by HG, and performed by MKG, TK and HG. Data analysis was performed by MKG and HG. Funding acquisition and project management were performed by MKG and HG. The manuscript was written by MKG and HG. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors are grateful to the G\u0026uuml;zey family for their logistical support, to G\u0026ouml;kben Kankılı\u0026ccedil; for her assistance with laboratory work, and to Mehmet Ali Kırpık from Kafkas University for providing laboratory facilities during the hibernation study conducted in Kars. We would like to thank Refik Ayata for developing the Excel-based macro used in this study. We would also like to express their gratitude once again to everyone who contributed to different parts of this study. These individuals have been acknowledged in the respective publications.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eArmitage KB (2003) Marmots: \u003cem\u003eMarmota monax\u003c/em\u003e and allies. 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Physiol Biochem Zool 83:135\u0026ndash;141. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1086/648736\u003c/span\u003e\u003cspan address=\"10.1086/648736\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"mammal-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"acth","sideBox":"Learn more about [Mammal Research](http://link.springer.com/journal/13364)","snPcode":"13364","submissionUrl":"https://www.editorialmanager.com/acth/default2.aspx","title":"Mammal Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Anatolia, ecological niche modelling, environmental gradients, phenotypic variation, Spermophilus xanthoprymnus","lastPublishedDoi":"10.21203/rs.3.rs-6474074/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6474074/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eGeographic variation in phenotypic traits offers key insights into how organisms adapt to diverse environmental conditions. In this study, we studied how elevational and associated environmental gradients shape geographic variation in the bioclimatic niche, hibernation, and body size of Anatolian ground squirrels (\u003cem\u003eSpermophilus xanthoprymnus\u003c/em\u003e). Specifically, we used presence data (170 out of 538 present records) from across the species\u0026rsquo; range, body temperature data from 51 free-living individuals in two natural populations located 880 km apart, and body size data from 167 individuals across 10 populations to explore geographic variation in bioclimatic niche, hibernation, and body size across elevational and associated environmental gradients. Our results revealed that the bioclimatic niches of two deeply divergent mitochondrial (mt)DNA lineages (i.e. the western and eastern lineages) are distinct. However, this pattern appears to result from the underlying bioclimatic differences between the regions the western and eastern lineages inhabit. Anatolian ground squirrels from the eastern population, which inhabits a higher-elevation, colder, wetter, and more seasonally variable environment, exhibit longer hibernation periods, spend a higher proportion of this period in torpor bouts, and achieve deeper reductions in body temperature than conspecifics from the western population. Adult males exhibit shorter hibernation periods and spend a smaller proportion of this period in torpor bouts than the other age-sex classes. Anatolian ground squirrels from the eastern lineage, which inhabits areas at higher elevations with colder, wetter, and more seasonally variable environments, are morphologically larger than conspecifics from the western lineage, particularly among males. Overall, our results demonstrate that spatial and environmental gradients shape phenotypic variation in Anatolian ground squirrels through lineage-, population- and demographic-level responses. By integrating bioclimatic niche, hibernation, and body size, this study highlights the importance of combining multiple trait dimensions to improve our understanding of eco-evolutionary divergence in hibernating mammals.\u003c/p\u003e","manuscriptTitle":"Geographic Variation in the Bioclimatic Niche, Hibernation, and Body Size of Anatolian Ground Squirrels","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 09:05:38","doi":"10.21203/rs.3.rs-6474074/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-04-29T13:49:15+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-29T07:44:12+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-23T01:54:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"Mammal Research","date":"2025-04-22T02:47:16+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"mammal-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"acth","sideBox":"Learn more about [Mammal Research](http://link.springer.com/journal/13364)","snPcode":"13364","submissionUrl":"https://www.editorialmanager.com/acth/default2.aspx","title":"Mammal Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a986f1c9-caca-4d3c-9aaa-cabbd292b301","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-22T16:02:47+00:00","versionOfRecord":{"articleIdentity":"rs-6474074","link":"https://doi.org/10.1007/s13364-025-00815-z","journal":{"identity":"mammal-research","isVorOnly":false,"title":"Mammal Research"},"publishedOn":"2025-09-19 15:56:55","publishedOnDateReadable":"September 19th, 2025"},"versionCreatedAt":"2025-05-07 09:05:38","video":"","vorDoi":"10.1007/s13364-025-00815-z","vorDoiUrl":"https://doi.org/10.1007/s13364-025-00815-z","workflowStages":[]},"version":"v1","identity":"rs-6474074","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6474074","identity":"rs-6474074","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}