Centre–Margin Dynamics in Dinoponera quadriceps (Hymenoptera, Formicidae): Abundance, Body Reduction and Functional Divergence

Centre–Margin Dynamics in Dinoponera quadriceps (Hymenoptera, Formicidae): Abundance, Body Reduction and Functional Divergence | 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 Centre–Margin Dynamics in Dinoponera quadriceps (Hymenoptera, Formicidae): Abundance, Body Reduction and Functional Divergence Sabrina Medeiros, Bruno Mayrink, Jhonathan Silva, Ricardo Campos, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9336875/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Central–marginal hypothesis predicts that populations occurring at the periphery of a species’ geographic distribution experience more adverse environmental conditions, resulting in reduced population density, lower fitness, and potential morphological changes. In insects, morphological traits are closely associated with ecological performance and resource acquisition, making them useful indicators of how populations respond to environmental gradients. Here, we investigated whether populations of the ant Dinoponera quadriceps differ in abundance and morphofunctional traits between the center and edge of the species’ geographic distribution along the Espinhaço Mountain Range, Brazil. Ants were sampled using pitfall traps in two sites approximately 610 km apart. Generalized Linear Mixed Models were used to evaluate differences in abundance and trait variation between sites, and a Principal Component Analysis summarized multivariate body size variation. The abundance of D. quadriceps was significantly higher in central populations and was positively correlated with the richness of other ant species. Individuals from the marginal population exhibited significantly smaller overall body size. Additionally, trait-specific differences emerged, with marginal individuals displaying larger cephalic index, longer femora, and larger eyes. These findings suggest that peripheral environments impose energetic constraints that reduce body size while favoring morphological adjustments that enhance locomotor and sensory efficiency, highlighting the importance of intraspecific functional variation in understanding species responses at geographic range limits. Ant ecology Geographic range limits Phenotypic variation Species distribution Trait-based ecology Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction A central tenet in biogeography is that a species' geographic distribution is shaped by its capacity to maintain viable populations across varying environmental gradients (Sexton et al., 2009 ). According to the central–marginal hypothesis, peripheral populations are often exposed to more adverse or suboptimal environmental conditions compared to central populations, which typically occupy more stable and favorable habitats (see Brown, Stevens and Kaufman, 1996 ; Pironon et al., 2017 ). Consequently, central populations are expected to exhibit higher densities and superior performance, whereas edge populations may experience demographic decline and reduced fitness (Holt and Barfield, 2011 ; Eriksson and Rafajlovic, 2022 ). Environmental and demographic shifts at range margins often drive significant changes in morphological patterns, including reduced trait variability and smaller body size due to energetic constraints, stabilizing selection, and intensified genetic drift (Kirkpatrick and Barton, 1997 ; Arnett and Gotelli, 1999 ; Braz et al., 2023 ). Furthermore, the occupation of suboptimal habitats may reinforce such differences, favoring phenotypes with greater metabolic efficiency under stressful conditions, typical of range limits (Pyron, 1999 ; Economo et al., 2015 ). In social insects such as ants, morphological traits are closely tied to ecological performance and niche breadth (Guilherme et al., 2019 ). The interplay between environmental filters and morphological adaptation is particularly evident in traits related to resource acquisition and locomotion (see Wahl et al., 2015 ). For instance, mandible and clypeus size, as well as head length and width, are associated with prey capture, manipulation, and processing capacity, in addition to reflecting bite force and feeding efficiency (Gronenberg, 1995 ; Paul, 2001 ; Larabee, Gronenberg and Suarez, 2017 ). Similarly, eye width is related to visual perception and foraging activity (Esquivel et al., 2017 ), whereas antennal scape length is linked to sensory efficiency and environmental exploration (Elgar et al., 2018 ). Metafemur length is associated with locomotion and displacement capacity during foraging (Sommer and Wehner, 2012 ), while Weber’s length is a classical indicator of body size, often correlated with metabolic costs, dispersal ability, and tolerance to environmental stressors (Abeikova et al., 2022 ). Importantly, an integrated analysis of these morphofunctional traits allows for a robust assessment of the functional performance and adaptive potential of populations subjected to distinct environmental pressures at the limits of their distribution (Gronenberg, 1995 ; Sexton et al. 2009 ; Sommer and Wehner 2012 ; Larabee, Gronenberg and Suarez 2017 ). The Neotropical ant Dinoponera quadriceps (Formicidae: Ponerinae), which lacks morphologically differentiated queens, provides an ideal model for testing these dynamics due to its specialized biology and wide environmental tolerance (Medeiros and Araújo 2014 ; Vieira et al., 2024 ). This omnivore ant (Medeiros et al., 2012 ) is found in the Caatinga, Cerrado, and Atlantic forest formations, occurring throughout much of northeastern Brazil (Batista et al., 2021 ). This broad distribution reflects its adaptation to environments characterized by high temperatures and pronounced climatic seasonality (Araújo and Rodrigues, 2006 ; Medeiros and Araújo, 2014 ). Beyond its wide range, the species exhibits a distinctive social structure in which a single fertile worker (gamergate) assumes the reproductive role (Monnin and Peeters, 1998 ). Foraging is solitary and guided by chemical and spatial cues, with workers showing high fidelity to specific paths while hunting for a generalist diet (Azevedo et al., 2021 ; Vieira et al., 2024 ). The combination of solitary foraging and a broad geographic reach suggests that morphological traits related to resource acquisition and manipulation are under strong selective pressure across varying environmental conditions (Guilherme et al., 2019 ). Thus, it is reasonable to expect differentiation of morphological traits among populations in response to local conditions, potentially enhancing energetic efficiency during foraging in distinct habitats. In this study, we compared population density and morphofunctional traits of D. quadriceps between populations located at the center and at the southern edge of the species’ geographic distribution. While most studies on range limits focus on community-level shifts in species presence or richness (Eckert et al.,2008; Pironon et al., 2017 ), there is a significant knowledge gap regarding how individuals within a single species adjust their phenotype to survive at the edge of their ecological tolerance. We addressed this by testing two premises of the central–marginal distribution hypothesis: (i) populations located at the center of the species’ distribution exhibit higher abundance, as environmental resources are expected to be more suitable and predictable in central areas (Eriksson and Rafajlovic, 2022 ); (ii) edge populations consist of individuals with smaller body size compared to those from central populations, due to greater energetic constraints at the range limits (Economo et al., 2015 ). Finally, by moving beyond simple body size, we hypothesized that individuals at the margins exhibit adaptations in multivariate traits linked to increased locomotor and sensory efficiency, alongside greater among-individual variation. Material and methods Study area and site characterization The populations of Dinoponera quadriceps targeted in this study were located in Serra Geral (15°00′27″S, 43°00′49″W) and Serra dos Morgados (10°14′42″S, 40°14′06″W), both situated within the Espinhaço Range. The Espinhaço Range extends for over 1,200 km across the states of Minas Gerais and Bahia, forming one of the most ancient and biologically unique landscapes in Brazil (Fernandes et al ., 2016, Oswald et al. 2025). The two sampling sites (Serra Geral and Serra dos Morgados) are approximately 610 km apart and are situated at elevations of 890 m and 960 m above sea level, respectively. The climate at both sites is markedly seasonal, with a dry and cooler period extending from April to September and a warm and rainy season from October to March. At Serra Geral, the mean annual temperature is approximately 24°C with mean annual precipitation of 830 mm (Fagundes et al., 2022 ). Serra dos Morgados presents a slightly warmer and drier climate, with a mean annual temperature of 26°C and annual precipitation of approximately 650 mm (Cavalcanti et al ., 2006). The predominant vegetation type at both sites is Seasonal Deciduous Forest, characterized by the dominance of plant species that lose at least 50% of their leaves during the prolonged dry season (Quezada et al ., 2009). Based on the known geographic distribution of D. quadriceps and the relative location of the sampling sites relative to the species’ range limits, the population from Serra dos Morgados was classified as ‘central’, whereas the population from Serra Geral was classified as ‘marginal’ (Fig. 1 ). Ant sampling Ant sampling was carried out during the 2024 rainy season. At each site, three 900 m² plots (30 × 30 m), spaced at least 150 m apart from each other. In each plot, five pitfall traps were buried at ground level at the vertices and the center, totaling 30 traps across both sites. The traps consisted of a 1L plastic containers filled with 500 mL of a preservative solution (10 mL neutral detergent, 490 mL water, and 10g NaCl). The traps remained in the field for 48 h. Sampled ants were stored in 70% ethanol and transported to the INSECTA collection (Center for Biology and Insect Taxonomy at Universidade Estadual de Montes Claros, Unimontes). Specimens were sorted and identified using the taxonomic keys of Baccaro et al. ( 2015 ) and Feitosa et al. (2024), supplemented by the AntWeb database and consultation with specialists. Morphofunctional Trait Measurements A total of 36 individuals of D. quadriceps (18 individuals per site) were used to characterize morphofunctional traits. We measured head length (HL), head width (HW), Weber’s length (WL), clypeus width (CW), antennal scape length (SL), eye length (EL), metafemur length (MFL), and mandible length (MdL) (Fig. 2 ). The cephalic index (CI) was calculated as CI = HW/HL x 100. These structures were selected as they represent functional adaptations to environmental conditions, specifically resource acquisition, locomotion and sensory perception (Kaspari and Weiser, 2002 ; Davidson, Cook and Snelling, 2004 ; Weiser and Kaspari, 2006 ; Bihn, Gebauer and Brandl, 2010 ). All measurements were performed using a ZEISS Stemi 305 stereomicroscope equipped with an Axiocam 208 color camera and ZEISS ZEN (ver. 3.2) imaging software. Statistical Analysis Generalized Linear Mixed Models (GLMMs) were used to evaluate the effects of site location (central vs. marginal) and local ant richness (excluding D. quadriceps ) species on the abundance of D. quadriceps (n = 30 traps). In these models, the abundance of D. quadriceps was considered the response variable, while the collection sites, the species richness of other ants, and the interaction between site and species richness were considered explanatory variables. Abundance data were modeled using a Poisson distribution with a log-link function and treating sampling plots as random factor. Model significance was tested with analysis of variance (ANOVA) and the Chi-squared test (“Chisq”) by anova function of the carr package in R version 4.5.2 (R Development Core Team, 2025 ). To assess whether overall body size differed between central and marginal populations, first we ordinated the individuals from both populations using a Principal Component Analysis (PCA) based on the correlation matrix of seven morphofunctional traits measured for the 36 individuals. Subsequently, scores from the first PCA axis (PC1) were compared using a GLM in which the collection site was used as the explanatory variable and PC1 scores (assumed to follow a Gaussian distribution) were the response variable. This served as a proxy for multi-trait body size variation. Finally, we compared each individual morphofunctional trait between central and marginal populations using separate GLMs. Thus clypeus width (CW), antennal scape length (SL), eye length (EL), metafemur length (MFL), mandible length (MdL), cephalic index (CI), or Weber’s length (WL) were the response variables (assumed to follow a Gaussian distribution) and the collection site was the explanatory variable. To account for allometric effects, all traits were standardized by Weber’s length (WL) prior to analysis (Oliveira et al., 2020). The significance of these models was assessed using ANOVA and F-test. All statistical analyses were conducted in R version 4.5.2 (R Development Core Team, 2025 ). Results A total of 45 individuals of D. quadriceps were sampled across the two study sites (central = 27; marginal = 18). The mean ant abundance per pitfall trap varied significantly as a function of sampling site and the richness of other ant species (Table 1 ). Specifically, the mean abundance of D. quadriceps was 50% higher in the central population than in the marginal population (Fig. 3 A). In addition, D. quadriceps abundance was positively correlated with the richness of other ant species (Fig. 3 B). Table 1 Results of the Generalized Linear Mixed Model (GLMM) evaluating the effects of site, other ant species richness and, the interactions between this variables on the abundance of Dinoponera quadriceps . Response Variable Explanatory Variable Estimate Std. Error z X 2 P Abundance Site 1.055 0.398 2.649 10.46 0.0081 Richness 0.260 0.082 3.182 13.88 < 0.001 Interaction 0.252 0.159 1.578 2.4886 0.114 The first two PCA axes accounted for 50.7% of the total variation in the size of the morphofunctional traits of D. quadriceps (PC1 = 35.5%; PC2 = 15.2%). Overall, central population clustered positively along PC1, showing strong associations with WL, CW, SL, EL, and MdL, whereas the marginal population was negatively associated with this axis (Fig. 4 a). Give measurements of the main morphofunctional traits were used in the PCA, would be reasonavel think that the first axis likely represents overall body size in D. quadriceps . Accordingly, PC1 scores were significantly higher in the central population than in the marginal population (Deviance = 973.89, F = 12.088, P = 0.0014; Fig. 4 b), indicating that individuals from the central population exhibit a larger overall body size than those from the range margin. Analysis of individual traits revealed specific morphological divergences between sites. Individuals from the central population exhibited a significantly greater Weber’s length than those from the marginal population (Table 2 ; Fig. 5 A). Conversely, individuals from the central population displayed a lower cephalic index, shorter metafemur length, and shorter eye length compared to individuals from the marginal population (Fig. 5 B, C, D). The another morphofunctional traits as mandible length, scape length and, clypeus width did not differ significantly between the two populations (Table 2 ; Fig. 5 E, F, G). Table 2 Results of the Generalized Linear Model (GLM) evaluating the effects of sites (marginal or central) on the morphofunctional traits of Dinoponera quadriceps . Response Variable Estimate Std. Error F P Weber length 294.580 67.850 18.848 0.0001 Metafemur length 0.075 0.033 5.281 0.0278 Eye length -0.007 0.003 5.216 0.0287 Cephalic index -0.002 0.001 10.252 0.0029 Mandible length -0.011 0.013 0.670 0.4186 Scape length -0.019 0.016 1.490 0.2306 Clypeus width -0.002 0.010 0.049 0.8254 Discussion Our results are broadly consistent with the centre–margin hypothesis, as we observed higher density of Dinoponera quadriceps in the central site, and individuals from the marginal population exhibited a significant reduction in body size. Here it is important salient that ant worker abundance was estimated based on the number of individuals captured in pitfall traps. However, pitfall captures represent a proxy for worker activity outside the nest rather than absolute colony number (Vasconcellos, Santana and Souza, 2004 ; Segev et al., 2015 ; Maák et al., 2020 ). In adition, worker activity in D. quadriceps is strongly influenced by local climatic conditions, with the number of workers captured per pitfall negatively correlated with temperature (Medeiros et al. 2012 ). Given that Serra dos Morgados experiences higher temperatures than Serra Geral (Fagundes et al., 2022 ; Cavalcanti et al., 2006), differences in activity patterns between sites may partially influence the observed abundance patterns. Therefore, the higher activity density recorded in the central population should be interpreted cautiously and may not directly reflect differences in colony density. In this context, the number of sampling units and the spatial scope of the study should be considered when extrapolating these patterns, particularly given potential local heterogeneity in ant activity and resource distribution. Notwithstanding these considerations, the consistency and direction of the observed differences between central and marginal populations suggest that the detected patterns are robust and align with theoretical expectations of the centre–margin hypothesis. Regardless of the sampling site, we observed a positive correlation between the abundance of D. quadriceps and the richness of other ant species. This pattern suggests that environmental factors, such as habitat heterogeneity and resource availability at a local scale, may promote both increased species richness and higher abundance of D. quadriceps (see Neves et al., 2013 ; Kuchenbecker et al., 2018; Deák et al., 2021 ). Structurally complex environments can provide a wider range of nesting sites and food resources, thereby increasing resources availability and supporting both community diversity and ant activity (Kovalenko, Thomaz and Warfe, 2012 ). The PCA and Weber’s length comparisons indicated that individuals of D. quadriceps from the central population exhibited larger overall body size. Although PC1 was used as a proxy for body size, this interpretation assumes that all traits loaded positively on this axis and should be considered an approximation of multivariate size variation rather than a direct measure. The reduction in body size at the margin is consistent with expectations of energetic and developmental constraints imposed by suboptimal habitats (e.g., Economo et al. 2015 ; Braz et al. 2023 ). In insects, body size is strongly influenced by resource availability during development; smaller phenotypes often emerge when energetic intake is limited (Brown, Stephens and Kaufman, 1996; Holt and Barfield, 2011 ). Our findings suggest that marginal D. quadriceps populations may be operating closer to their physiological and energetic limits, leading to the observed ‘morphological reduction’. However, because developmental conditions were not directly measured, this interpretation remains inferential and alternative mechanisms, such as phenotypic plasticity or genetic drift, cannot be excluded. It is also worth noting that the number of individuals included in the morphometric analyses may influence the sensitivity to detect subtle trait differences, particularly for non-significant comparisons; nevertheless, the overall pattern of reduced body size at the margin remained consistent across analytical approaches. Crucially, we found that morphological responses were trait-specific rather than uniform. Individuals from the marginal population exhibited a larger cephalic index, longer femora, and greater eye length, whereas mandible, antennal scape, and clypeus width did not differ. This pattern suggests that peripheral environments do not merely constrain ant body size but reshape functional trait combinations. Because most traits were standardized by Weber’s length, these differences primarily reflect variation in shape rather than absolute size, indicating potential shifts in proportional investment among traits. The relatively larger head (cephalic index) and eyes at the margin may be consistent with a functional strategy in which enhanced visual perception in the more open, heterogeneous environment typical of range limits, while longer femora may be associated with increased locomotor efficiency and exploratory range (Wahl et al., 2015 ; Sommer and Wehner, 2012 ). In a solitary forager like D. quadriceps (Azevedo et al., 2014 ; 2021 ), being longer-legged and better-sighted at the margin could be a vital adaptation to find spatially dispersed prey. In contrast, the stability of mandibles and clypeus length suggests intense stabilizing selection on traits directly linked to prey capture and chemical communication, which are functionally non-negotiable for this species’ ecology. In summary, our study demonstrates that the effects of range margins on species may not be fully captured by activity-based abundance metrics alone, but are also reflected in patterns of intraspecific morphological variation. We provide evidence that D. quadriceps exhibits reduced overall body size at the range margin alongside shifts in trait proportions, i.e. to lower metabolic costs while simultaneously investing in traits that maximize foraging efficiency (legs and eyes), although the underlying mechanisms (e.g., adaptive responses, plasticity, or demographic processes) remain unresolved. Importantly, even under a relatively limited sampling design (n = 30 traps and trait measures in 36 individuals), the consistency of these morphofunctional patterns reinforces the predictive strength of the centre–margin hypothesis in shaping trait distributions within species. This study highlights why ant functional ecology must move beyond simple abundance metrics; intraspecific variation can reveal the hidden stress of marginal populations long before a demographic reduction occurs. As climate change continues to shift environmental conditions creating new gradients, understanding these morphofunctional adjustments will be critical for predicting the persistence of apex invertebrate predators at their geographic boundaries. Future studies integrating environmental measurements, behavioral data, and experimental approaches will be essential to determine whether the observed trait variation translates into differences in ecological performance or fitness. Declarations Competing Interests and Funding : The authors declare no competing interests. This research was supported by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), grant numbers APQ-02806/22 and APQ-05253/23. The authors also acknowledge financial support in the form of scholarships from CNPq (grant #311243/2023-1) and FAPEMIG (FCT-00331-25). Author Contribution M.F. and T.C. - Conceptualization, funding acquisition, methodology, supervision, review and editing, statistical analysis - S.M. and B.M. data curation, figures preparation and write the original manuscript - J.S. and R.C. formal analysis, writing and review manuscript. All authors reviewed the manuscript to submission. References Abeikova L, Boudinot BE, Beutel RG et al (2022) The skeletomuscular system of the mesossoma of Formica rufa workers (Hymenoptera: Formicidae). Insect Syst Divers 6:1–6. https://doi.org/10.1093/isd/ixac002 Araújo A, Rodrigues Z (2006) Foraging behavior of the queenless ant Dinoponera quadriceps Stantschi (Hymenoptera: Formicidae). Neotrop Entomol 35:159–164. https://doi.org/10.1590/S1519-566X2006000200002 Arnett AE, Gotelli NJ (1999) Bergmann’s rule in ant lion Mymeleon immaculatus DeGeer (Neuroptera: Myrmeleontidae): geographic variation in body size and heterozygosity. 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Annu Rev Ecol Evol Syst 40:415–436. https://doi.org/10.1146/annurev.ecolsys.110308.120317 Sommer S, Wehner R (2012) Leg allometry in ants: extreme long-leggedness in thermophilic species. Arthropod Struct Dev 41:71–77. https://doi.org/10.1016/j.asd.2011.08.002 Vasconcellos A, Santana GG, Souza AK (2004) Nest spacing and architecture of Dinoponera quadriceps . Braz J Biol 64:357–362. https://doi.org/10.1590/S1519-69842004000200022 Vieira MEL, Teseo S, Azevedo DLO, Châline N, Araújo A (2024) Competition through ritualized aggressive interactions between sympatric colonies in solitary foraging ants. Sci Nat 111. https://doi.org/10.1007/s00114-024-01891-y Weiser MD, Kaspari M (2006) Ecological morphospace of New World ants. Ecol Entomol 31:131–142. https://doi.org/10.1111/j.0307-6946.2006.00759.x Wahl V, Pfeffer S, Wittlinger M (2015) Walking and running in the desert ant Cataglyphis fortis . J Comp Physiol A 201:645–656. https://doi.org/10.1007/s00359-015-0999-2 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-9336875","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":624587818,"identity":"082376f2-83a4-4cb6-8220-945f592424a8","order_by":0,"name":"Sabrina Medeiros","email":"","orcid":"","institution":"Universidade Estadual de Montes Claros","correspondingAuthor":false,"prefix":"","firstName":"Sabrina","middleName":"","lastName":"Medeiros","suffix":""},{"id":624587819,"identity":"fb2095ce-5ae7-4997-97da-8c71e0837b3f","order_by":1,"name":"Bruno Mayrink","email":"","orcid":"","institution":"Universidade Estadual de Montes Claros","correspondingAuthor":false,"prefix":"","firstName":"Bruno","middleName":"","lastName":"Mayrink","suffix":""},{"id":624587820,"identity":"9db2b7c1-9f03-475f-ba1f-07e8246cfb61","order_by":2,"name":"Jhonathan Silva","email":"","orcid":"","institution":"Universidade Federal do Vale do São Francisco","correspondingAuthor":false,"prefix":"","firstName":"Jhonathan","middleName":"","lastName":"Silva","suffix":""},{"id":624587821,"identity":"b2b48c73-1f14-4b49-9a6a-1bc005e41ce2","order_by":3,"name":"Ricardo Campos","email":"","orcid":"","institution":"Universidade Federal de Viçosa","correspondingAuthor":false,"prefix":"","firstName":"Ricardo","middleName":"","lastName":"Campos","suffix":""},{"id":624587822,"identity":"a52443f5-e490-49e0-907a-2914f9aaa5cb","order_by":4,"name":"Tatiana Cornelissen","email":"","orcid":"","institution":"Universidade Federal de Minas Gerais","correspondingAuthor":false,"prefix":"","firstName":"Tatiana","middleName":"","lastName":"Cornelissen","suffix":""},{"id":624587823,"identity":"b14e380b-80e8-431e-8469-4f839ccae3af","order_by":5,"name":"Marcilio Fagundes","email":"data:image/png;base64,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","orcid":"","institution":"Universidade Estadual de Montes Claros","correspondingAuthor":true,"prefix":"","firstName":"Marcilio","middleName":"","lastName":"Fagundes","suffix":""}],"badges":[],"createdAt":"2026-04-06 19:38:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9336875/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9336875/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107336845,"identity":"bda199f9-1f0a-4059-b927-9ced63b4a35f","added_by":"auto","created_at":"2026-04-20 13:42:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":262208,"visible":true,"origin":"","legend":"\u003cp\u003eMap illustrating the location of the sampling sites and the geographic distribution of\u003cem\u003e Dinoponera quadriceps \u003c/em\u003eaccording to Paiva \u0026amp; Brandão (1995) and GBIF.org (occurrence data), 2025.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/9194a54d497c784878733198.png"},{"id":107337006,"identity":"78a57e07-580d-438d-a829-14c612c09a9b","added_by":"auto","created_at":"2026-04-20 13:42:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":681281,"visible":true,"origin":"","legend":"\u003cp\u003eMorphofunctional traits measured in \u003cem\u003eDinoponera quadriceps\u003c/em\u003e: (MdL) mandible length, (EL) eye length, (CW) clypeus width, (HL) head length, (HW) head width, (SL) antennal scape length, (WL) Weber’s length and, (MFL) metafemur length.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/c8f6d97f9b65a4d1ac18a3d4.png"},{"id":107336927,"identity":"a2800916-f16f-4880-ad29-99809027cea3","added_by":"auto","created_at":"2026-04-20 13:42:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":118824,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in \u003cem\u003eDinoponera quadriceps\u003c/em\u003e abundance (mean ± SE) between marginal and central populations (A), and the relationship between \u003cem\u003eD. quadriceps\u003c/em\u003e abundance and the richness of other ant species (B). The asterisk (*) denotes a significant difference in abundance between populations (P = 0.0012), and the shaded area indicates the 95% confidence interval.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/6032db6a48eb13ab7cb13797.png"},{"id":107336847,"identity":"3317bddf-6fc7-4a72-809a-61b101b67964","added_by":"auto","created_at":"2026-04-20 13:42:10","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":165911,"visible":true,"origin":"","legend":"\u003cp\u003ePrincipal Component Analysis (PCA) based on morphofunctional traits (MFL: Metafemur Length, CW: Clypeus Width , EL: Eye Length, SL: Antennal Scape Length, WL: Weber Length, MdL: Mandible Length, CI: Cephalic index), of \u003cem\u003eDinoponera quadriceps\u003c/em\u003e individuals from central and marginal populations showing (A) a biplot ordering individual ants along two first PCA axes and the loadings of morphofunctional traits and (B) statistical variation in first Principal Component scores between marginal and central populations. Arrow length reflects the magnitude of each trait’s contribution, and direction indicates correlation with the principal components.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/eedac2548c710267c9d696bf.png"},{"id":107336930,"identity":"f05f30d5-84c9-496d-8ea6-744cd2c2f5c2","added_by":"auto","created_at":"2026-04-20 13:42:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":114010,"visible":true,"origin":"","legend":"\u003cp\u003eMorphofunctional traits variation between marginal and central populations. (A) Weber’s length, (B) metatibial length, (C) eye length, (D) cephalic index, (E) scape length, (F) mesosoma length, and (G) clypeus width (n = 36).\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/2a74f9f21d44b9038023d4dd.png"},{"id":107337042,"identity":"93a84604-4433-4d21-a114-98982b462a4c","added_by":"auto","created_at":"2026-04-20 13:42:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1580417,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9336875/v1/44037b70-5553-40c8-bfdb-55497760ac38.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Centre–Margin Dynamics in Dinoponera quadriceps (Hymenoptera, Formicidae): Abundance, Body Reduction and Functional Divergence","fulltext":[{"header":"Introduction","content":"\u003cp\u003eA central tenet in biogeography is that a species' geographic distribution is shaped by its capacity to maintain viable populations across varying environmental gradients (Sexton et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). According to the central\u0026ndash;marginal hypothesis, peripheral populations are often exposed to more adverse or suboptimal environmental conditions compared to central populations, which typically occupy more stable and favorable habitats (see Brown, Stevens and Kaufman, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Pironon et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Consequently, central populations are expected to exhibit higher densities and superior performance, whereas edge populations may experience demographic decline and reduced fitness (Holt and Barfield, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Eriksson and Rafajlovic, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Environmental and demographic shifts at range margins often drive significant changes in morphological patterns, including reduced trait variability and smaller body size due to energetic constraints, stabilizing selection, and intensified genetic drift (Kirkpatrick and Barton, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Arnett and Gotelli, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Braz et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Furthermore, the occupation of suboptimal habitats may reinforce such differences, favoring phenotypes with greater metabolic efficiency under stressful conditions, typical of range limits (Pyron, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Economo et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn social insects such as ants, morphological traits are closely tied to ecological performance and niche breadth (Guilherme et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The interplay between environmental filters and morphological adaptation is particularly evident in traits related to resource acquisition and locomotion (see Wahl et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). For instance, mandible and clypeus size, as well as head length and width, are associated with prey capture, manipulation, and processing capacity, in addition to reflecting bite force and feeding efficiency (Gronenberg, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Paul, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Larabee, Gronenberg and Suarez, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Similarly, eye width is related to visual perception and foraging activity (Esquivel et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), whereas antennal scape length is linked to sensory efficiency and environmental exploration (Elgar et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Metafemur length is associated with locomotion and displacement capacity during foraging (Sommer and Wehner, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), while Weber\u0026rsquo;s length is a classical indicator of body size, often correlated with metabolic costs, dispersal ability, and tolerance to environmental stressors (Abeikova et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Importantly, an integrated analysis of these morphofunctional traits allows for a robust assessment of the functional performance and adaptive potential of populations subjected to distinct environmental pressures at the limits of their distribution (Gronenberg, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Sexton et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Sommer and Wehner \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Larabee, Gronenberg and Suarez \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe Neotropical ant \u003cem\u003eDinoponera quadriceps\u003c/em\u003e (Formicidae: Ponerinae), which lacks morphologically differentiated queens, provides an ideal model for testing these dynamics due to its specialized biology and wide environmental tolerance (Medeiros and Ara\u0026uacute;jo \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Vieira et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This omnivore ant (Medeiros et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) is found in the Caatinga, Cerrado, and Atlantic forest formations, occurring throughout much of northeastern Brazil (Batista et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). This broad distribution reflects its adaptation to environments characterized by high temperatures and pronounced climatic seasonality (Ara\u0026uacute;jo and Rodrigues, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Medeiros and Ara\u0026uacute;jo, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Beyond its wide range, the species exhibits a distinctive social structure in which a single fertile worker (gamergate) assumes the reproductive role (Monnin and Peeters, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Foraging is solitary and guided by chemical and spatial cues, with workers showing high fidelity to specific paths while hunting for a generalist diet (Azevedo et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Vieira et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The combination of solitary foraging and a broad geographic reach suggests that morphological traits related to resource acquisition and manipulation are under strong selective pressure across varying environmental conditions (Guilherme et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Thus, it is reasonable to expect differentiation of morphological traits among populations in response to local conditions, potentially enhancing energetic efficiency during foraging in distinct habitats.\u003c/p\u003e \u003cp\u003eIn this study, we compared population density and morphofunctional traits of \u003cem\u003eD. quadriceps\u003c/em\u003e between populations located at the center and at the southern edge of the species\u0026rsquo; geographic distribution. While most studies on range limits focus on community-level shifts in species presence or richness (Eckert et al.,2008; Pironon et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), there is a significant knowledge gap regarding how individuals within a single species adjust their phenotype to survive at the edge of their ecological tolerance. We addressed this by testing two premises of the central\u0026ndash;marginal distribution hypothesis: (i) populations located at the center of the species\u0026rsquo; distribution exhibit higher abundance, as environmental resources are expected to be more suitable and predictable in central areas (Eriksson and Rafajlovic, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2022\u003c/span\u003e); (ii) edge populations consist of individuals with smaller body size compared to those from central populations, due to greater energetic constraints at the range limits (Economo et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Finally, by moving beyond simple body size, we hypothesized that individuals at the margins exhibit adaptations in multivariate traits linked to increased locomotor and sensory efficiency, alongside greater among-individual variation.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy area and site characterization\u003c/h2\u003e \u003cp\u003eThe populations of \u003cem\u003eDinoponera quadriceps\u003c/em\u003e targeted in this study were located in Serra Geral (15\u0026deg;00\u0026prime;27\u0026Prime;S, 43\u0026deg;00\u0026prime;49\u0026Prime;W) and Serra dos Morgados (10\u0026deg;14\u0026prime;42\u0026Prime;S, 40\u0026deg;14\u0026prime;06\u0026Prime;W), both situated within the Espinha\u0026ccedil;o Range. The Espinha\u0026ccedil;o Range extends for over 1,200 km across the states of Minas Gerais and Bahia, forming one of the most ancient and biologically unique landscapes in Brazil (Fernandes \u003cem\u003eet al\u003c/em\u003e., 2016, Oswald et al. 2025). The two sampling sites (Serra Geral and Serra dos Morgados) are approximately 610 km apart and are situated at elevations of 890 m and 960 m above sea level, respectively. The climate at both sites is markedly seasonal, with a dry and cooler period extending from April to September and a warm and rainy season from October to March. At Serra Geral, the mean annual temperature is approximately 24\u0026deg;C with mean annual precipitation of 830 mm (Fagundes et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Serra dos Morgados presents a slightly warmer and drier climate, with a mean annual temperature of 26\u0026deg;C and annual precipitation of approximately 650 mm (Cavalcanti \u003cem\u003eet al\u003c/em\u003e., 2006). The predominant vegetation type at both sites is Seasonal Deciduous Forest, characterized by the dominance of plant species that lose at least 50% of their leaves during the prolonged dry season (Quezada \u003cem\u003eet al\u003c/em\u003e., 2009). Based on the known geographic distribution of \u003cem\u003eD. quadriceps\u003c/em\u003e and the relative location of the sampling sites relative to the species\u0026rsquo; range limits, the population from Serra dos Morgados was classified as \u0026lsquo;central\u0026rsquo;, whereas the population from Serra Geral was classified as \u0026lsquo;marginal\u0026rsquo; (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAnt sampling\u003c/h3\u003e\n\u003cp\u003eAnt sampling was carried out during the 2024 rainy season. At each site, three 900 m\u0026sup2; plots (30 \u0026times; 30 m), spaced at least 150 m apart from each other. In each plot, five pitfall traps were buried at ground level at the vertices and the center, totaling 30 traps across both sites. The traps consisted of a 1L plastic containers filled with 500 mL of a preservative solution (10 mL neutral detergent, 490 mL water, and 10g NaCl). The traps remained in the field for 48 h. Sampled ants were stored in 70% ethanol and transported to the INSECTA collection (Center for Biology and Insect Taxonomy at Universidade Estadual de Montes Claros, Unimontes). Specimens were sorted and identified using the taxonomic keys of Baccaro et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and Feitosa \u003cem\u003eet al.\u003c/em\u003e (2024), supplemented by the AntWeb database and consultation with specialists.\u003c/p\u003e\n\u003ch3\u003eMorphofunctional Trait Measurements\u003c/h3\u003e\n\u003cp\u003eA total of 36 individuals of \u003cem\u003eD. quadriceps\u003c/em\u003e (18 individuals per site) were used to characterize morphofunctional traits. We measured head length (HL), head width (HW), Weber\u0026rsquo;s length (WL), clypeus width (CW), antennal scape length (SL), eye length (EL), metafemur length (MFL), and mandible length (MdL) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The cephalic index (CI) was calculated as CI\u0026thinsp;=\u0026thinsp;HW/HL x 100. These structures were selected as they represent functional adaptations to environmental conditions, specifically resource acquisition, locomotion and sensory perception (Kaspari and Weiser, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Davidson, Cook and Snelling, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Weiser and Kaspari, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Bihn, Gebauer and Brandl, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). All measurements were performed using a ZEISS Stemi 305 stereomicroscope equipped with an Axiocam 208 color camera and ZEISS ZEN (ver. 3.2) imaging software.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eGeneralized Linear Mixed Models (GLMMs) were used to evaluate the effects of site location (central vs. marginal) and local ant richness (excluding \u003cem\u003eD. quadriceps\u003c/em\u003e) species on the abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e (n\u0026thinsp;=\u0026thinsp;30 traps). In these models, the abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e was considered the response variable, while the collection sites, the species richness of other ants, and the interaction between site and species richness were considered explanatory variables. Abundance data were modeled using a Poisson distribution with a log-link function and treating sampling plots as random factor. Model significance was tested with analysis of variance (ANOVA) and the Chi-squared test (\u0026ldquo;Chisq\u0026rdquo;) by anova function of the carr package in R version 4.5.2 (R Development Core Team, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo assess whether overall body size differed between central and marginal populations, first we ordinated the individuals from both populations using a Principal Component Analysis (PCA) based on the correlation matrix of seven morphofunctional traits measured for the 36 individuals. Subsequently, scores from the first PCA axis (PC1) were compared using a GLM in which the collection site was used as the explanatory variable and PC1 scores (assumed to follow a Gaussian distribution) were the response variable. This served as a proxy for multi-trait body size variation.\u003c/p\u003e \u003cp\u003eFinally, we compared each individual morphofunctional trait between central and marginal populations using separate GLMs. Thus clypeus width (CW), antennal scape length (SL), eye length (EL), metafemur length (MFL), mandible length (MdL), cephalic index (CI), or Weber\u0026rsquo;s length (WL) were the response variables (assumed to follow a Gaussian distribution) and the collection site was the explanatory variable. To account for allometric effects, all traits were standardized by Weber\u0026rsquo;s length (WL) prior to analysis (Oliveira et al., 2020). The significance of these models was assessed using ANOVA and F-test. All statistical analyses were conducted in R version 4.5.2 (R Development Core Team, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 45 individuals of \u003cem\u003eD. quadriceps\u003c/em\u003e were sampled across the two study sites (central\u0026thinsp;=\u0026thinsp;27; marginal\u0026thinsp;=\u0026thinsp;18). The mean ant abundance per pitfall trap varied significantly as a function of sampling site and the richness of other ant species (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Specifically, the mean abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e was 50% higher in the central population than in the marginal population (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). In addition, \u003cem\u003eD. quadriceps\u003c/em\u003e abundance was positively correlated with the richness of other ant species (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB).\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 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of the Generalized Linear Mixed Model (GLMM) evaluating the effects of site, other ant species richness and, the interactions between this variables on the abundance of \u003cem\u003eDinoponera quadriceps\u003c/em\u003e.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResponse Variable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExplanatory Variable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEstimate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStd. Error\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ez\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eX\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbundance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSite\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.398\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.649\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.0081\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRichness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.082\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.182\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e13.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInteraction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.252\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.159\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.578\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.4886\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.114\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe first two PCA axes accounted for 50.7% of the total variation in the size of the morphofunctional traits of \u003cem\u003eD. quadriceps\u003c/em\u003e (PC1\u0026thinsp;=\u0026thinsp;35.5%; PC2\u0026thinsp;=\u0026thinsp;15.2%). Overall, central population clustered positively along PC1, showing strong associations with WL, CW, SL, EL, and MdL, whereas the marginal population was negatively associated with this axis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Give measurements of the main morphofunctional traits were used in the PCA, would be reasonavel think that the first axis likely represents overall body size in \u003cem\u003eD. quadriceps\u003c/em\u003e. Accordingly, PC1 scores were significantly higher in the central population than in the marginal population (Deviance\u0026thinsp;=\u0026thinsp;973.89, F\u0026thinsp;=\u0026thinsp;12.088, P\u0026thinsp;=\u0026thinsp;0.0014; Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), indicating that individuals from the central population exhibit a larger overall body size than those from the range margin.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAnalysis of individual traits revealed specific morphological divergences between sites. Individuals from the central population exhibited a significantly greater Weber\u0026rsquo;s length than those from the marginal population (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA). Conversely, individuals from the central population displayed a lower cephalic index, shorter metafemur length, and shorter eye length compared to individuals from the marginal population (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB, C, D). The another morphofunctional traits as mandible length, scape length and, clypeus width did not differ significantly between the two populations (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e; Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eE, F, G).\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 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of the Generalized Linear Model (GLM) evaluating the effects of sites (marginal or central) on the morphofunctional traits of \u003cem\u003eDinoponera quadriceps\u003c/em\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResponse Variable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEstimate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStd. Error\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeber length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e294.580\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67.850\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18.848\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.0001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMetafemur length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.033\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.281\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.0278\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEye length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.216\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.0287\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCephalic index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10.252\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.0029\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMandible length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.670\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.4186\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScape length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.490\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.2306\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClypeus width\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.049\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8254\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur results are broadly consistent with the centre\u0026ndash;margin hypothesis, as we observed higher density of \u003cem\u003eDinoponera quadriceps\u003c/em\u003e in the central site, and individuals from the marginal population exhibited a significant reduction in body size. Here it is important salient that ant worker abundance was estimated based on the number of individuals captured in pitfall traps. However, pitfall captures represent a proxy for worker activity outside the nest rather than absolute colony number (Vasconcellos, Santana and Souza, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Segev et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Ma\u0026aacute;k et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In adition, worker activity in \u003cem\u003eD. quadriceps\u003c/em\u003e is strongly influenced by local climatic conditions, with the number of workers captured per pitfall negatively correlated with temperature (Medeiros et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Given that Serra dos Morgados experiences higher temperatures than Serra Geral (Fagundes et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Cavalcanti et al., 2006), differences in activity patterns between sites may partially influence the observed abundance patterns. Therefore, the higher activity density recorded in the central population should be interpreted cautiously and may not directly reflect differences in colony density. In this context, the number of sampling units and the spatial scope of the study should be considered when extrapolating these patterns, particularly given potential local heterogeneity in ant activity and resource distribution. Notwithstanding these considerations, the consistency and direction of the observed differences between central and marginal populations suggest that the detected patterns are robust and align with theoretical expectations of the centre\u0026ndash;margin hypothesis.\u003c/p\u003e \u003cp\u003eRegardless of the sampling site, we observed a positive correlation between the abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e and the richness of other ant species. This pattern suggests that environmental factors, such as habitat heterogeneity and resource availability at a local scale, may promote both increased species richness and higher abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e (see Neves et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Kuchenbecker et al., 2018; De\u0026aacute;k et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Structurally complex environments can provide a wider range of nesting sites and food resources, thereby increasing resources availability and supporting both community diversity and ant activity (Kovalenko, Thomaz and Warfe, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe PCA and Weber\u0026rsquo;s length comparisons indicated that individuals of \u003cem\u003eD. quadriceps\u003c/em\u003e from the central population exhibited larger overall body size. Although PC1 was used as a proxy for body size, this interpretation assumes that all traits loaded positively on this axis and should be considered an approximation of multivariate size variation rather than a direct measure. The reduction in body size at the margin is consistent with expectations of energetic and developmental constraints imposed by suboptimal habitats (e.g., Economo et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Braz et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In insects, body size is strongly influenced by resource availability during development; smaller phenotypes often emerge when energetic intake is limited (Brown, Stephens and Kaufman, 1996; Holt and Barfield, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Our findings suggest that marginal \u003cem\u003eD. quadriceps\u003c/em\u003e populations may be operating closer to their physiological and energetic limits, leading to the observed \u0026lsquo;morphological reduction\u0026rsquo;. However, because developmental conditions were not directly measured, this interpretation remains inferential and alternative mechanisms, such as phenotypic plasticity or genetic drift, cannot be excluded. It is also worth noting that the number of individuals included in the morphometric analyses may influence the sensitivity to detect subtle trait differences, particularly for non-significant comparisons; nevertheless, the overall pattern of reduced body size at the margin remained consistent across analytical approaches.\u003c/p\u003e \u003cp\u003eCrucially, we found that morphological responses were trait-specific rather than uniform. Individuals from the marginal population exhibited a larger cephalic index, longer femora, and greater eye length, whereas mandible, antennal scape, and clypeus width did not differ. This pattern suggests that peripheral environments do not merely constrain ant body size but reshape functional trait combinations. Because most traits were standardized by Weber\u0026rsquo;s length, these differences primarily reflect variation in shape rather than absolute size, indicating potential shifts in proportional investment among traits. The relatively larger head (cephalic index) and eyes at the margin may be consistent with a functional strategy in which enhanced visual perception in the more open, heterogeneous environment typical of range limits, while longer femora may be associated with increased locomotor efficiency and exploratory range (Wahl et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Sommer and Wehner, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). In a solitary forager like \u003cem\u003eD. quadriceps\u003c/em\u003e (Azevedo et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), being longer-legged and better-sighted at the margin could be a vital adaptation to find spatially dispersed prey. In contrast, the stability of mandibles and clypeus length suggests intense stabilizing selection on traits directly linked to prey capture and chemical communication, which are functionally non-negotiable for this species\u0026rsquo; ecology.\u003c/p\u003e \u003cp\u003eIn summary, our study demonstrates that the effects of range margins on species may not be fully captured by activity-based abundance metrics alone, but are also reflected in patterns of intraspecific morphological variation. We provide evidence that \u003cem\u003eD. quadriceps\u003c/em\u003e exhibits reduced overall body size at the range margin alongside shifts in trait proportions, \u003cem\u003ei.e.\u003c/em\u003e to lower metabolic costs while simultaneously investing in traits that maximize foraging efficiency (legs and eyes), although the underlying mechanisms (e.g., adaptive responses, plasticity, or demographic processes) remain unresolved. Importantly, even under a relatively limited sampling design (n\u0026thinsp;=\u0026thinsp;30 traps and trait measures in 36 individuals), the consistency of these morphofunctional patterns reinforces the predictive strength of the centre\u0026ndash;margin hypothesis in shaping trait distributions within species. This study highlights why ant functional ecology must move beyond simple abundance metrics; intraspecific variation can reveal the hidden stress of marginal populations long before a demographic reduction occurs. As climate change continues to shift environmental conditions creating new gradients, understanding these morphofunctional adjustments will be critical for predicting the persistence of apex invertebrate predators at their geographic boundaries. Future studies integrating environmental measurements, behavioral data, and experimental approaches will be essential to determine whether the observed trait variation translates into differences in ecological performance or fitness.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting Interests and Funding\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests. This research was supported by the Funda\u0026ccedil;\u0026atilde;o de Amparo \u0026agrave; Pesquisa do Estado de Minas Gerais (FAPEMIG), grant numbers APQ-02806/22 and APQ-05253/23. The authors also acknowledge financial support in the form of scholarships from CNPq (grant #311243/2023-1) and FAPEMIG (FCT-00331-25).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eM.F. and T.C. - Conceptualization, funding acquisition, methodology, supervision, review and editing, statistical analysis - S.M. and B.M. data curation, figures preparation and write the original manuscript - J.S. and R.C. formal analysis, writing and review manuscript. All authors reviewed the manuscript to submission.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbeikova L, Boudinot BE, Beutel RG et al (2022) The skeletomuscular system of the mesossoma of \u003cem\u003eFormica rufa\u003c/em\u003e workers (Hymenoptera: Formicidae). 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J Comp Physiol A 201:645\u0026ndash;656. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00359-015-0999-2\u003c/span\u003e\u003cspan address=\"10.1007/s00359-015-0999-2\" 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":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ant ecology, Geographic range limits, Phenotypic variation, Species distribution, Trait-based ecology","lastPublishedDoi":"10.21203/rs.3.rs-9336875/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9336875/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Central\u0026ndash;marginal hypothesis predicts that populations occurring at the periphery of a species\u0026rsquo; geographic distribution experience more adverse environmental conditions, resulting in reduced population density, lower fitness, and potential morphological changes. In insects, morphological traits are closely associated with ecological performance and resource acquisition, making them useful indicators of how populations respond to environmental gradients. Here, we investigated whether populations of the ant \u003cem\u003eDinoponera quadriceps\u003c/em\u003e differ in abundance and morphofunctional traits between the center and edge of the species\u0026rsquo; geographic distribution along the Espinha\u0026ccedil;o Mountain Range, Brazil. Ants were sampled using pitfall traps in two sites approximately 610 km apart. Generalized Linear Mixed Models were used to evaluate differences in abundance and trait variation between sites, and a Principal Component Analysis summarized multivariate body size variation. The abundance of \u003cem\u003eD. quadriceps\u003c/em\u003e was significantly higher in central populations and was positively correlated with the richness of other ant species. Individuals from the marginal population exhibited significantly smaller overall body size. Additionally, trait-specific differences emerged, with marginal individuals displaying larger cephalic index, longer femora, and larger eyes. These findings suggest that peripheral environments impose energetic constraints that reduce body size while favoring morphological adjustments that enhance locomotor and sensory efficiency, highlighting the importance of intraspecific functional variation in understanding species responses at geographic range limits.\u003c/p\u003e","manuscriptTitle":"Centre–Margin Dynamics in Dinoponera quadriceps (Hymenoptera, Formicidae): Abundance, Body Reduction and Functional Divergence","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-20 13:40:30","doi":"10.21203/rs.3.rs-9336875/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"368e05dd-1f78-453f-8130-ccdac4cadfd4","owner":[],"postedDate":"April 20th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-04-30T01:07:20+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-12T06:42:40+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-20 13:40:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9336875","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9336875","identity":"rs-9336875","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}