Phoretic mite communities associated with Ips typographus (Linnaeus, 1758) and Ips duplicatus (Sahlber, 1836) (Coleoptera: Scolytinae) in a Norway spruce stand

Phoretic mite communities associated with Ips typographus (Linnaeus, 1758) and Ips duplicatus (Sahlber, 1836) (Coleoptera: Scolytinae) in a Norway spruce stand | 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 Phoretic mite communities associated with Ips typographus (Linnaeus, 1758) and Ips duplicatus (Sahlber, 1836) (Coleoptera: Scolytinae) in a Norway spruce stand Dragoș Toma, Gabriela Isaia, Minodora Manu, Carol Dieter Simon This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6528419/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Experimental and Applied Acarology → Version 1 posted You are reading this latest preprint version Abstract European spruce bark beetle Ips typographus (Linnaeus, 1758) is considered the most destructive and aggressive pest of Norway spruce in Europe. Recently, Ips duplicatus (Sahlberg, 1836), another species of bark beetle, primarily affecting the genus Picea , has expanded its range westwards in Europe. In spruce stands, bark beetle populations are closely associated with various organisms such as fungi, nematodes, and mites. Mites, due to the lack of specialized dispersal organs for covering long distances, use bark beetles through a phenomenon known as phoresy. While phoretic mites and their relationship with Ips typographus have been extensively studied in Europe, very few studies have focused on the populations of phoretic mites associated with Ips duplicatus . The aim of this study is to analyze and document the communities of phoretic mites and their complex relationship with the two species of bark beetles in the same location. The research was conducted in a stand located at the lower limit of spruce, where the two pest species have developed outbreaks together. Over 50,000 beetles were collected using wing-type pheromone traps, of which 4,348 were analyzed for the determination of phoretic mites (2,413 Ips typographus ; 1,935 Ips duplicatus ). In total, nine species of phoretic mites were identified, of which only six were found on Ips duplicatus . Among the nine species, Dendrolaelaps disetus (Hirschmann, 1960), Elattoma sp. , and Paraleius leontonychus (Berlese, 1910) are reported for the first time in Romania. The results highlighted that although Ips typographus beetles were significantly more phorezed than Ips duplicatus beetles throughout the entire flight period, the peaks of phoretic rates were similar. ONE-WAY PERMANOVA test revealed significant differences between the two phoretic mite communities, differences also highlighted by diversity indices. These differences are most likely due to the presence of certain mite species only on Ips typographus beetles, as well as differences between the populations of common species. Regarding the location of phoretic mites on the insects' bodies, this varied depending on the mite species and the host. bark beetle phoresy phoretic mites Picea abies community Romania Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Norway spruce ( Picea abies (L.) H. Karst) is considered the most important gymnosperm species in Europe (Caudullo et al. 2016; Skrøppa 2003; Westin and Haapanen 2013), covering an area of approximately 30 million hectares (Jansson et al. 2013). In Romania, it is the second most widespread tree species (Șofletea and Curtu 2008), where, both in pure and mixed forests, it occupies around 28% of the country's forested area (Sidor et al. 2015). Considering its ecological and especially economic importance, due to the exceptional quality of its wood (Caudullo et al. 2016; Westin and Haapanen 2013), the range of Norway spruce has been expanded over the past two centuries through artificial plantations outside its natural ranges (Caudullo et al. 2016; Jansson et al. 2013; Nețoiu et al. 2008), in areas characteristic of deciduous species (Jansson et al. 2013; Klimo et al. 2000). Abiotic factors such as severe storms or extreme drought weaken and physiologically impair Norway spruce stands, particularly those outside their natural range (Caudullo et al. 2016; Spiecker 2000), thus creating favorable conditions for the outbreaks of bark beetles (Caudullo et al. 2016; Simionescu et al. 2000; Wermelinger 2004). The most destructive and aggressive pest among the bark beetles of Norway spruce is the European spruce bark beetle, Ips typographus (Linne 1758) (Caudullo et al. 2016; Marini et al. 2013; Netherer et al. 2019; Simionescu et al. 2000; Wermelinger 2004). Considered to be a species that normally colonizes dead or dying trees, during mass outbreaks it can also attack healthy trees (Simionescu et al. 2000; Wermelinger 2004; Weslien et al. 1989). In the past century, I. typographus outbreaks have led to the partial or total dieback of millions of cubic meters of spruce trees in Europe (Grégoire and Evans 2004). Recently, Ips duplicatus (Sahlberg 1836), another bark beetle species of conifers, has expanded its range (Olenici et al. 2009, 2022; Wermelinger et al. 2020), being considered an invasive species in Europe (Olenici et al. 2022; Zúbrik et al. 2006) and introduced in quarantine list by the European Union (Holuša et al. 2012). Although it attacks several species within the genus Picea and occasionally Pinus , Larix , and Pseudotsuga (Duduman et al. 2013; Kašák and Foit 2015; Pfeffer and Knížek 1995; Wermelinger et al. 2020), it prefers Norway spruce stands, particularly those outside their natural range (Olenici et al. 2009, 2022; Wermelinger et al. 2020), where it causes outbreaks of varying intensity (Grodzki 2003; Holuša et al. 2003; Olenici et al. 2009, 2011). Sometimes, the attack of I. duplicatus on Norway spruce trees occurs together with I. typographus (Grodzki 2012), as the species share similar behavior and biology (Wermelinger et al. 2020). In Romania, Ips duplicatus is now present in the vast majority of Norway spruce cultivation areas (Olenici et al. 20022). Tree dieback in outbreak areas is not only the result of bark beetle attacks but also of pathogenic fungi with which the beetles associate and introduce into the wood (Lieutier 2002; Linnakoski et al. 2016; Moser et al. 2010; Paine et al. 1997; Wermelinger 2004). I. typographus is considered the bark beetle species most commonly associated with pathogenic fungi (Krokene and Solheim 1996). Numerous studies have shown that, in addition to pathogenic fungi, bark beetle populations are closely linked to other organisms such as nematodes or mites (Forsse 1987; Hofstetter et al. 2015; Moser and Bogenschütz 1984). Mite species, due to their lack of specialized legs for traveling long distances, use bark beetles for dispersal through a phenomenon called phoresy (Bartlow and Agosta 2021; Camerik 2010; White et al. 2017). These mites mainly belong to the orders Mesostigmata and Trombidiformes (Moser and Roton 1971; Moser 1985; Vissa and Hofstetter 2017). For dispersal to occur, phoresy must include three fundamental stages: host location, attachment to the host, and detachment at the appropriate time (Bartlow and Agosta 2021). Phoresy does not involve parasitic relationships, although it can become antagonistic to host species over time. A large number of phoretic organisms attached to the host body can somewhat affect the host's locomotion ability (Gwiazdowicz et al. 2011). Moreover, when a phoretic relationship forms between two organisms, it can evolve into a parasitic relationship (White et al. 2017). In the case of Ips typographus , following the significant outbreaks it caused in Norway spruce stands across Europe (Bakke 1983; Simionescu et al. 2000; Wermelinger 2004), interest in this pest has grown considerably, leading to intensive studies on the relationship between bark beetle populations and their phoretic mites. To date, numerous studies have focused on this aspect, with over 60 species of phoretic mites being identified in close association with the European spruce bark beetle, I. typographus (Gwiazdowicz 2008; Skorupski and Gwiazdowicz 1998). On the other hand, the phoretic mite species, their abundance, and the relationship they have with the bark beetle Ips duplicatus have been very little studied, with only one study conducted in Europe so far (Čejka and Holuša 2014). Furthermore, a comparative analysis of the phoretic mite populations associated with the two bark beetle species, which coexist and jointly attack trees in an outbreak, has not been conducted. In this context, through this study, we aim to determine and analyze the following aspects: (i) the populations of phoretic mites associated with Ips typographus and Ips duplicatus ; (ii) the attachment preference of phoretic mite species based on their host; (iii) the dynamic of the phoresy of the two bark beetle species throughout the entire growing season; (iv) comparative analysis of phoretic mite populations based on their host. 2. Materials and methods 2.1. Study area The research was conducted in a Norway spruce stand near Râșnov (45°35 N; 25°28 E), Brașov County, managed by the Râșnov Town Forest Administration, in forest compartment 72B (Fig. 1 ). The stand is 80 years old and it is situated at an altitude of 715 m, at the lower limit of the Norway spruce range. Ips duplicatus has been reported in this area since 2011 (Duduman et al. 211). 2.2. Collection and analysis of entomological material Bark beetles were collected using six intercept traps (wing type), three baited with a commercial pheromone AtraTYP specific to Ips typographus and three baited with a commercial pheromone AtraDUP specific to Ips duplicatus , both produced by the Raluca Ripan Institute of Chemistry, Romania. The distance between the two trap arrays was 25 m, while the distance between traps within the arrays was 50 m. The traps were set up on May 2, 2023, at 10–12 m from the forest edge, and bark beetles were collected every 7–11 days throughout the entire growing season, with the last collection in mid-September. The collected beetles were stored in a freezer at a temperature of -5°C to prevent the detachment of phoretic mites from their hosts (Moser and Bogenschuütz 1984; Paraschiv and Isaia 2020). Subsequently, from each capture, the bark beetles were identified, and a sample of 50 specimens was retained for the analysis of phoretic mites. If the number of bark beetles per trap was less than 50 specimens, all available specimens were analyzed (Blaženec and Jakuš 2009; Paraschiv and Isaia 2020). Insect sex determination was performed through dissection based on their genitalia (Duduman et al. 2019, 2022). Regarding the phoretic mites on the bodies of the beetles, after the species identification their numbers were recorded based on the location of attachment to the beetle bodies. The mite species were identified using identification keys provided by the scientific literature (Ghiliarov and Bregetova 1977; Kinn 1968; Khaustov 2000; Moser and Bogenschuütz 1984; Rahiminejad et al. 2011, Trach and Khustov 2018). To determine the attachment preference of the phoretic mites to their hosts, the bodies of the bark beetles were subdivided into several parts: head, thorax, abdomen, first, second and third pair of legs, elytral declivity, and under elytra (Paraschiv and Isaia 2020). Beetle sex determination was performed using a stereomicroscope. The taxonomical identification/cheking of the phoretic mites was performed using a Zeiss Axio Scope A 1 microscope. Photos of the phoretic mite species identified in this study were taken with a CX43 microscope equipped with a Promicam Lite Digital Camera. Voucher specimens of all mite species detected in this study are stored at the laboratory of the "Marin Drăcea" National Institute for Research and Development in Forestry, Voluntari, Ilfov. 2.3. Statistical Analysis The zoocenological analysis of mite communities was evaluated using the dominance index (D), categorized as follows: eudominant (> 30%), dominant (15.01–30%), sub-dominant (7.01–15%), resident (3.01–7%), and sub-resident ( 50%), constant (30.01–50%), subconstant (15.01–30%), accessory species (5.01–15%), and accidental occurrence (< 5%), as used in other studies (Gwiazdowicz et al. 2011; Paraschiv and Isaia 2020). Dominance (D) was calculated by dividing the total number of individuals of a phoretic mite species by the total number of phoretic mites. Frequency (F) was determined as the ratio of the total number of bark beetle with a specific species of phoretic mites to the total number of analyzed beetles. Phoresy rate was determind by the ratio between beetles that carried mites and total number of beetles analyzed. The application of the Shapiro-Wilk test confirmed the normal distribution of the data, and Levene's test verified the homogeneity of the data, thus meeting the requirements for the application of parametric tests. In order to evaluate if the intensity of phoresy and the phoresy rate were influenced by factors such as bark beetle species, collection date or beetle sex, and to determine the most phorezed body parts of the each bark beetle species and the attachment preference of each mite species for a specific body part of their hosts, One-Way ANOVA analysis of variance was conducted. The significance level of the differences between variables was established using Tukey's multiple test. Due to the low number of attached phoretic mites the attachment on the first, second and third pair of legs and the head in the case of Ips typographus and the attaachment on the head and the third pair of legs in the case of Ips duplicatus were not included in the statistical analyses. If the number of specimens for a species was insufficient for this analysis, or if individuals of a species did not exhibit a specific preference for any particular body part, it was noted that the species had no distinct attachment preference. The characterization and evaluation of the differences between the phoretic mite populations of the two bark beetle species were determined using diversity indices such as the Shannon diversity index (H’), Simpson index (1-D), Evenness index (e^H/S), and Berger-Parker index, along with the PERMANOVA test (Anderson 2014; Isaia et al. 2022; Magurran 2004). The application of the PERMANOVA test on the two communities was conducted based on Bray-Curtis dissimilarity and 9999 random permutations. To ensure that the effect of the dominant species ( Dendrolaelaps quadrisetus Berlese 1920) did not overly influence the analysis results, the data were transformed using the log10(x + 1) function (Isaia et al. 2022). To visualize the differences between the phoretic mite assemblage populations of the two bark beetle species, non-metric multidimensional scaling (NMDS) was employed (Revainera et al. 2019). For the primary data processing and graphical presentation of the dynamics of the phoretic rate in relation to the capture levels of the two bark beetle species, Microsoft Excel (Microsoft Corp., Redmond, Washington, USA) was used. Normality testing, homogeneity, and statistical differences were performed using STATISTICA 8.0 software (Weiß 2007). The diversity indices, PERMANOVA test, and NMDS were conducted with PAST 4.03 (Hammer and Harper 2001). 3. Results 3.1. The dynamics of insect flight and phoresy rates During the entire vegetation season, a total of 55,276 bark beetles were captured in the pheromone traps, 51,222 of them were I. typographus and 4,054 were I. duplicatus . The two species reached their peak flight intensity at different times. For I. typographus , the highest number of beetles was recorded in the second decade of May, while for I. duplicatus , the highest number of beetles was recorded in the first decade of July. Out of the total captured beetles, 2,413 specimens of I. typographus were subsequently analyzed to determine the phoretic mites, resulting a phoresy rate of 49.3%. For I. duplicatus , 1,935 beetles were analyzed, of which only 20.6% carried phoretic mites on their bodies. The differences between the two species were significant (df = 1, f = 133.8, p 0.05; df = 1, f = 2.09, p > 0.05). Regarding the dynamics of phoresy rates over time, significant fluctuations were observed for both I. typographus (df = 17, f = 5.195, p < 0.05) and I. duplicatus (df = 17, f = 4.7542, p < 0.05). For I. typographus (Fig. 2a), the phoresy rate reached its first peak at the beginning of the flight (May 9 – May 16), followed by two more peaks at the beginning of August (August 3 – August 10) and at the end of the flight (August 28 – September 3). Although at a considerably lower intensity, the phoresy rate for I. duplicatus exhibited peaks similar to those recorded for I. typographus (Fig. 2b). The first and most significant peak for I. duplicatus was recorded at the beginning of the flight (May 9 – May 16), followed by two additional peaks at the end of July (July 20 – July 27) and at the end of the flight (August 28 – September 3). Interestingly, the lowest of phoresy rates recorded for I. typographus was close in values to the peaks of phoresy rates of I. duplicatus , as a result of the phoretic load between the two species. 3.2. Species composition and zoocenological analysis The phoretic mites identified on the body of Ips typographus belong to nine species, namely: Dendrolaelaps quadrisetus (Berlese 1920), Dendrolaelaps disetus (Hirschmann 1960), Elattoma sp., Histiostoma piceae (Scheucher 1957), Paraleius leontonychus (Berlese 1910), Pleuronectocelaeno austriaca (Vitzthum 1926), Proctolaelaps fiseri (Samsinak 1960), Trichouropoda polytricha (Vitzthum 1923), and Uroobovella ipidis (Vitzthum 1923) (Table 1 ). The most frequent and dominant species on the bodies of I. typographus beetles was Dendrolaelaps quadrisetus , which represented more than half of the total (63.46%). Specimens of this species, along with specimens of the species Uroobovella ipidis , Histiostoma piceae , and Trichouropoda polytricha , accounted for a total of 98% of the entire mite population, while the other species were classified as having accidental dominance and accidental occurrence frequency. Only six species of mites were found on the bodies of I. duplicatus beetles, with their dominance being more evenly distributed compared to I. typographus (Table 1 ). Although Dendrolaelaps quadrisetus was one of the most dominant and frequent species, it was not the most abundant; that position was held by the genus Elattoma . Elattoma sp., Dendrolaelaps quadrisetus and Trichouropoda polytricha represented approximately 86% of the total mite population in the case of I. duplicatus . The frequency of the mite species identified on I. duplicatus was much lower, not exceeding 10% for any of the species. The species Elattoma sp. was the only species that was more abundant on the Ips duplicatus beetles compared to the Ips typographus beetles. Table 1 Phoretic mite species of Ips typographus and Ips duplicatus , their dominance, frequency and feeding behavior. Family Species Feeding Behavior a Ips typographus Ips duplicatus Abundance Dominance (%) b Frequency (%) b Abundance Dominance (%) b Frequency (%) b Digamasellidae Dendrolaelaps quadrisetus Predacious 1963 63.46 eudominant 34.29 constant 186 31.85 eudominant 9.6 accesory species Digamasellidae Dendrolaelaps disetus Predacious 2 0.07 accidental 0.08 accidental occurrence 0 - - Pygmephoridae Elattoma sp. Mycetophagous 5 0.16 accidental 0.2 accidental occurrence 197 33.73 eudominant 5.58 accidental Histiostomatidae Histiostoma piceae Unknown 376 12.28 sub-dominant 8.15 accessory species 62 10.62 sub-dominant 2.32 accidental occurrence Oribatulidae Paraleius leontonychus Unknown 11 0.36 accidental 0.5 accidental occurrence 0 - - Neotenogyniidae Pleuronectocelaeno austriaca Predacious 9 0.29 accidental 0.33 accidental occurrence 0 - - Melicharidae Proctolaelaps fiseri Predacious 27 0.88 accidental 0.95 accidental occurrence 1 0.17 accidental 0.05 accidental occurrence Trematuridae Trichouropoda polytricha Unknown 298 9.73 sub-dominant 9.15 accessory species 121 20.72 dominant 4.55 accidental occurrence Urodinychidae Uroobovella ipidis Unknown 391 12.77 sub-dominant 9.31 accessory species 17 2.91 accidental 0.77 accidental occurrence a According to Hofstetter et al. (2014) b Classification according to Gwiazdowicz et al. (2011) 3.3. Community diversity and structure The diversity indices show significant differences between the two analyzed communities of phoretic mites (Table 2 ). In the case of the Shannon (H), Simpson, and Evenness indices, the results indicate that the phoretic mite community associated with the bark beetle I. duplicatus is more diverse and uniformly distributed. The considerably higher value recorded for the Berger-Parker index in the phoretic mite community of I. typographus indicates that it was dominated by a single species. Table 2 Diversity indices of the two community Diversity index Ips typographus Ips duplicatus Shannon_H 1.13 1.409 Evenness_e^H/S 0.344 0.682 Simpson_1-D 0.5564 0.7297 Berger-Parker 0.6346 0.3373 The result of the permutational analysis of variance (PERMANOVA) indicates a significant difference in the composition of the phoretic mite communities associated with the two bark beetle species (F = 30.58, p < 0.001). The NMDS analysis shows that, although the two populations do not completely differentiate from each other, the community associated with the bark beetle Ips typographus is much more centered, showing a tendency to separate from the community of Ips duplicatus (Fig. 3). The low stress level of the NMDS plot (0.14) indicates a good fit of the distances between points, making it a valid representation of the composition of the two phoretic mite communities (Magurran 2004). 3.4. Location of phoretic mites on the bodies of bark beetles Significant differences were recorded between the average number of phoretic mites attached to different body parts for both bark beetle species. For Ips typographus , the highest average number of mites was recorded under the elytra (1.85), significantly differing from the other parts (df = 4, f = 38.44, p < 0.05): thorax (0.33), elytral declivity (0.27), elytra (0.27), and abdomen (0.23) (Fig. 5a). In the case of Ips duplicatus , the highest average number of mites was also found under the elytra (0.33), significantly differing from the other parts (df = 6, f = 10.43, p < 0.05) (Fig. 5b). The next preferred attachment sites were the elytral declivity (0.19), abdomen (0.17), and the thorax (0.16). Although the average number of phoretic mites differs between the two hosts, the results regarding the localization of mites on their bodies are similar, with the majority of mites located under the elytra in both species, followed by the thorax, abdomen, pairs of legs, and elytra. Additionally, the less frequented areas for mites were the heads of the hosts and pairs of legs 3 in both species of bark beetles. The distribution of phoretic mites on host bodies is not random; it varies depending on the host species and the species of phoretic mites. For both Ips duplicatus and Ips typographus , the majority of specimens of Dendrolaelaps quadrisetus were identified under the hosts' elytra, with the differences statistically supported by the other locations (DF 8; F 52.31; p < 0.05; DF 8; F 44.93; p < 0.05). Although the few specimens of Elattoma sp. detected on Ips typographus did not show a preference for any specific body part, those identified on Ips duplicatus were mainly located in the area between pairs of legs 1 and 2, on the abdomen or thorax, significantly differing (DF 8; F 4.772; p < 0.05) from the rest of the body parts. Notable differences in attachment between the two hosts were also observed for the species Histiostoma piceae , Trichouropoda polytricha , and Uroobovella ipidis . However, it is worth noting a particular behavior in some specimens of Histiostoma piceae located under the hosts’ elytra in hyperphoresis with some specimens of Dendrolaelaps quadrisetus (Fig. 6 ). The only specimen of Proctolaelaps fiseri identified on Ips duplicatus was found on the abdomen, whereas specimens identified on Ips typographus did not show a specific preference, with most located under and on the elytra (DF 8; F 1.376; p > 0.05). The attachment preference of the species Pleuronectocelaeno austriaca on Ips typographus was predominantly under the elytra (DF 8; F 3.224; p 0.05). The only two specimens of Dendrolaelaps disetus were identified on the thorax of Ips typographus . Table 3 Main location of mites on the hosts body Species Distribution of mites on the body of Ips duplicatus Distribution of mites on the body of Ips typographus Location Proportion of total mites (%) Location Proportion of total mites (%) Dendrolaelaps quadrisetus Under elytra 95 Under elytra 88 Dendrolaelaps disetus - Thorax 100 Elattoma sp . Abdomen 34 Did not not show a preference Thorax 31 Histiostoma piceae Abdomen 29 Elytra 36 Thorax 26 Abdomen 23 Paraleius leontonychus - Did not not show a preference Pleuronectocelaeno austriaca - Under elytra 78 Proctolaelaps fiseri Abdomen 100 Did not not show a preference Trichouropoda polytricha Elytral declivity 79 Elytral declivity 36 Thorax 23 Uroobovella ipidis Thorax 24 Thorax 34 Abdomen 24 Pairs of legs 1 25 4. Discussion 4.1. The dynamics of insect flight and phoretic rates From its first report in Romania in the mid-20th century (Negru and Ceianu 1957) until now, the northern bark beetle Ips duplicatus has become a commonly encountered species in Romania, particularly in spruce forests outside its natural range (Olenici et al. 2022). In the sample area where this study was conducted, this pest was reported for the first time in 2011 (Duduman et al. 2011). Several studies indicate that Ips duplicatus is a secondary pest that primarily colonizes trees aged between 30 and 70 years in the upper part of the crown, where the bark is thinner (Bakke 1975; Lekander et al. 1977; Postner 1974). The secondary character of this pest is also reflected in our study's results, where captures recorded for Ips typographus are significantly higher than those for the northern bark beetle. The advanced age of the trees in the sample area does not suit the preferences of Ips duplicatus , thereby maintaining the population at a low level. The fact that Ips typographus was the dominant species may also explain the preference of phoretic mites in choosing hosts for transportation to other habitats. The rate of phoresy for Ips typographus beetles varied between 29% and 65%, with an average of 49.3%, representing the highest phoresy rate recorded in Romania (Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016) and in Europe (Gwiazdowicz et al. 2011, 2012; Zach et al. 2016; Milosavljević et al. 2022; Moser and Bogenschuütz 1984; Moser et al. 1989a; Takov et al. 2009). These differences in results from studies conducted to date can be explained in various ways, starting from the method of preserving the bark beetles up to the moment of their analysis. In the case of beetles preserved in alcohol (ethanol), there is a risk that some phoretic mites may detach (Moser and Bogenschuütz 1984), which is the main reason why the beetles collected during the study were stored as quickly as possible at negative temperatures in freezers. Additionally, other factors that could influence the capture rate of phoretic mites might include the age of the bark beetle outbreak (Peralta Vázquez 2018), the dynamics and density of the host beetle population (Paraschiv and Isaia 2020), or the location where the beetles overwinters, with those overwintering in the litter having lower chances of being phoresed by mites (Annila 1969). These hypotheses may explain why Ips duplicatus beetles were significantly less phoresed than Ips typographus . The phoresy rate of phoretic mites on Ips duplicatus beetles varied from 3–45%, with an average of 20.6%. The fact that adult Ips duplicatus primarily overwinter in the litter (Olenici et al. 2009; Zhang 1995) may explain the low capture percentage of phoretic mites; however, from the results obtained (Fig. 1 b), the highest percentages were reached at the beginning of the flight of the hibernating generation, although they did not reach the values of the hibernating generation of Ips typographus (Fig. 1 a). The hypotheses suggesting that outbreak age, density, and population dynamics may influence the relationship between phoretic mites and bark beetles appear to be closer to the truth. Given that Ips duplicatus is a new species in the Romanian fauna and its presence in the study area was reported only in 2011, this may explain the low capture percentage. Furthermore, some species of mites might prefer individuals of the dominant species in the outbreak over other secondary species. In this context, the research conducted by Poliță et al. (2016), which analyzed the relationship between phoretic mites and bark beetles Ips typographus and Pityogenes chalcographus (Linnaeus, 1761) in spruce stands aged 80–110 years, yielded similar results, with Ips typographus specimens being more phoresed than Pityogenes chalcographus . Additionally, another study analyzing the populations of phoretic mites associated with bark beetles of pine trees in Portugal showed that the specimens of the primary pest Ips sexdentatus (Boerner 1776) carried more mites than the specimens of the secondary pest Hylurgus ligniperda (Fabricius 1787) (Vissa et al. 2019). Although the intensities varied between the two analyzed species, the percentages of phoretic mite captures on hosts peaked during similar periods. The first and most significant peak occurred at the beginning of the insect flight in the first decade of May, the second peak was reached in the second decade of July and early August, when the number of beetles caught in traps significantly decreased, and the last peak was observed at the end of August and the beginning of September, coinciding with the end of the adults' flight. The results obtained are similar with the research conducted by Paraschiv and Isaia (2020). Furthermore, their study indicates that most phoretic mites were transported by the hibernating generation of beetles and those from the second generation. Considering that both Ips typographus and Ips duplicatus typically have two generations per year in Romania (Olenici et al., 2009; Simionescu et al. 2000), this observation aligns with the results obtained in this study. Although phoretic mites did not show a preference for the sex of the beetles from either species, a finding confirmed in other studies (Paraschiv et al. 2018; Paraschiv and Isaia 2020), males transported more mites than females. This aspect may be due to the fact that males of both species come into contact with more females (Lubojacký and Holuša 2013; Simionescu et al. 2000), thus increasing the probability that males will be phoresed. In this regard, a study conducted in Georgia on the pathogens of Ips typographus beetles found that males were more infested with a species of protozoan than females (Burjanadze and Goginashvili 2009). 4.2. Species composition and zoocenological analysis The total number of phoretic mite species identified in this study on Ips typographus is the highest reported in Romania compared to the other three studies conducted to date (Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016). This result is greater than or comparable to the findings from studies conducted in the Czech Republic (Čejka and Holuša 2014; Holuša and Čejka 2020), Turkey (Cilbircioğlu et al. 2021), Serbia (Milosavljević et al. 2022), Bulgaria (Takpv et al. 2009), Georgia (Burjanadze et al. 2008), Poland (Gwiazdowicz et al. 2011), Slovakia (Zach et al. 2016), and Croatia (Wirth et al. 2016), but considerably lower than the results from other studies conducted in Germany (Moser and Bogenschuütz 1984), Sweden (Moser et al. 1989a), Poland (Gwiazdowicz et al. 2012, 2015), and Finland (Penttinen et al. 2013). The differences between these results can be explained by the methods of preserving and storing entomological material (Paraschiv and Isaia 2020), the specifics of the area where the insects were collected, the total number of beetles analyzed (Gwiazdowicz et al. 2011), or the methods used for identifying mites, whether on the bodies of the insects or in their galleries. For example, a study conducted in Russia that analyzed mites associated with Ips typographus both on their bodies and from galleries identified over 60 species of phoretic mites closely linked to their hosts (Khaustov et al. 2018). The species identified in this study on the bodies of Ips typographus beetles are relatively common species also found in other studies, although three of them are reported for the first time in Romania: Paraleius leontonychus , Dendrolaelaps disetus , and Elattoma sp. The most abundant and dominant species, Dendrolaelaps quadrisetus , has been found in Europe not only on Ips typographus (Moser and Bogenschuütz 1984; Penttinen et al. 2013; Takov et al. 2009) but also on specimens of Ips sexdentatus (Paraschiv et al. 2018; Vissa et al. 2019), Pityokteines curvidens (Pernek et al. 2012), Pityogenes chalcographus (Poliță et al. 2016), Ips duplicatus (Čejka and Holuša 2014), Orthotomicus erosus (Vissa et al. 2019), Hylurgus ligniperda (Vissa et al. 2019), Polygraphus polygraphus (Michalski et al. 1992), and Ips acuminatus (Cilbircioğlu et al. 2021). Furthermore, this species has also been found on various bark beetle species in North America, such as Ips pini , Dendroctonus frontalis , and Dendroctonus valens (Hofstetter et al. 2015). This species exhibits a generalist behavior regarding its phoretic host and inhabits a wide range of habitats (Moser 1996). The fact that this species was the most frequently encountered is not unexpected, as similar results have been reported in other studies (Gwiazdowicz et al. 2011, 2015; Holuša and Čejka 2020; Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016). On the contrary, the other species from the genus Dendrolaelaps identified in this study, Dendrolaelaps disetus , is specific to Ips typographus (Hofstetter et al. 2015) and has so far been found in Germany (Moser and Bogenschuütz 1984) and Poland (Skorupski and Gwiazdowicz 1998). Species from the genus Dendrolaelaps are predatory, typically feeding on small organisms found in the galleries of bark beetles (Kinn 1983). However, several studies indicate that Dendrolaelaps quadrisetus may also increase the mortality of bark beetles (Penttinen et al. 2013) by consuming their eggs and larvae (Khaustov et al. 2018; Maslov 2006; Pernek et al. 2008). Similar feeding behavior is exhibited by Proctolaelaps fiseri and Pleuronectocelaeno austriaca . Like Dendrolaelaps quadrisetus , Proctolaelaps fiseri is a generalist phoretic mite species, reported on several species of bark beetles (Hofstetter et al. 2015; Khaustov et al. 2018; Paraschiv and Isaia 2020) in various habitats across Eurasia and North America (Khaustov et al. 2018). The low number of specimens identified in this study aligns with results from other studies (Paraschiv and Isaia, 2020; Penttinen et al. 2013; Poliță et al. 2016), often being classified as a rare, accidental species. Pleuronectocelaeno austriaca has so far been found in association with Ips typographus (Hofstetter et al. 2015), Scolytus scolytus (Moser et al. 2010), and Scolytus laevis (Vitzthum 1926), having been reported in Romania (Manu et al. 2017), Poland (Gwiazdowicz et al. 2015), the Czech Republic (Holuša and Čejka 2020), and Austria (Moser et al. 2010; Vitzthum 1926). These reports may indicate that the range of this species is in Central and Eastern Europe. The low number of specimens may be attributed to the size of this phoretic mite species, which may obstract the attachment with the host (Moser et al., 1989a). The two species from the suborder Uropodina, namely Trichouropoda polytricha and Uroobovella ipidis , are commonly found in high abundance in several studies focusing on the phoretic mites associated with the bark beetle Ips typographus (Holuša and Čejka 2020; Khaustov et al. 2018; Manu et al. 2017; Moser et al. 1989a; Penttinen et al. 2013; Paraschiv and Isaia 2020; Takov et al. 2009), as well as other species of bark beetles (Hofstetter et al. 2015). The relationship between these two species and their hosts is unknown; they most likely use insects solely for transportation (Paraschiv and Isaia 2020). However, some studies suggest that species from the genera Trichouropoda and Uroobovella may act as vectors for spores of fungi that alter wood color (Cardoza et al. 2008; Roets et al. 2014), and Trichouropoda polytricha could be a predator of nematodes in the galleries of bark beetles (Kinn 1982). Histiostoma piceae inhabits the galleries of a large number of bark beetles (Hofstetter et al. 2015; Pernek et al. 2008, 2012; Wirth et al. 2016) across Eurasia, showing a greater affinity for habitats rich in fungal spores (Hofstetter et al. 2013). Specimens of this species can be vectors for certain pathogenic fungi that significantly reduce the resistance of host trees, ultimately leading to their death (Moser et al. 1989a). Thus, the relationship between this species and bark beetles can be beneficial for both organisms involved in the phoretic process. Although Paraleius leontonychus is most often found in low abundance (Cilbircioğlu et al. 2021; Moser and Bogenschuütz 1984; Pernek et al. 2008), it is a species with a wide distribution in the bark galleries of many insects (Ahadiyat and Akrami 2015). Its feeding behavior is unknown, although some authors suggest that it may be a detritivorous species (Penttinen et al. 2013; Pernek et al. 2008). Additionally, this species may act as a vector for pathogenic fungi (Moser et al. 1989b, 1997) The 12 species from the genus Elattoma known to date are considered mycetophagous, and some of them can transport spores of pathogenic fungi (Rahiminejad et al. 2011). These species form phoretic relationships with several bark beetles (Rahiminejad et al. 2011) but are considered as rare and infrequent (Moser et al. 1989a; Hofstetter et al. 2013). This observation aligns with the results obtained for Ips typographus beetles but not for Ips duplicatus , where specimens of the genus Elattoma were the most abundant, being, in fact, the only phoretic mite species that exhibited this preference. The only species from the genus Elattoma that forms phoretic relationships more with Ips duplicatus than with Ips typographus is Elattoma crossi (Khaustov et al. 2018). This species, which has been identified in the Siberian taiga (the native range of Ips duplicatus beetles), may have been introduced to Romania with the migration of the beetles towards Southeast Europe. However, since the species could not be accurately identified, this remains only a hypothesis. The only study that focused on identifying species of mites associated with Ips duplicatus , in Europe, identified only 3 species of phoretic mites on the bodies of the insects, namely Trichouropoda polytricha , Uroobovella ipidis , and Dendrolaelaps quadrisetus (Čejka and Holuša 2014), a significantly lower number compared to the 6 species identified in this study. However, it is worth mentioning that the study in the Czech Republic did not target Ips duplicatus beetles throughout the entire vegetation season but only a small sample of insects collected at the beginning of the flight period. The species Histiostoma piceae and Proctolaelaps fiseri are recorded for the first time as forming phoretic relationships with this host. This aspect can be explained by the large number of hosts used by these two species for transportation to other habitats (Hofstetter et al. 2015; Khaustov et al. 2018). 4.3. Community diversity and structure The species of phoretic mites and their abundance on the host varied between the native bark beetle species and the invasive species. Diversity indices indicate that the phoretic mite community of Ips duplicatus is more homogeneous and uniform than the bark beetle community of Ips typographus . Although the phoretic mite population of Ips typographus was richer in species, the importance and weight of the dominant species, Dendrolaelaps quadrisetus , was very high. This aspect is especially observable in the values obtained for the Berger-Parker index, which expresses the proportional importance of the most abundant species in a community (Berger and Parker 1970). The results of the PERMANOVA analysis show that the two communities differ significantly from each other. Similar results were obtained by Vissa et al. (2019), who analyzed the phoretic mite communities of three species of pine bark beetles in Portugal. These results further reinforce the proposed hypothesis that the phoretic mite communities of different species of bark beetles differ in terms of abundance and species structure. Although phoretic mite species, in general, exhibit a generalist behavior regarding host selection and are rather specific to certain habitats (Pfammatter et al. 2016), most species identified in this study recorded a higher number on Ips typographus beetles compared to Ips duplicatus beetles. It is possible that some species of phoretic mites, at the local level, may exhibit host specificity when selecting a host for transportation to a new subcortical microhabitat (Lindquist 1970), even though globally they are associated with a wide range of bark beetles. This hypothesis is supported by the findings of Knee et al. (2013), where, out of 29 analyzed species of bark beetles, approximately 70% of the identified phoretic mite species were associated with only one or two bark beeltles. Factors such as the phenology, behavior of the bark beetle, or the microhabitat created by the host in its galleries may play a significant role in host selection (Knee et al. 2013). Additionally, the fact that Ips duplicatus is a relatively new species in the respective area cannot be overlooked, which may have limited its ability to establish strong relationships with all the mite species identified in this study. Another factor that may have influenced the choice of vectors for transporting phoretic mites is the size of the two species of bark beetles, with Ips duplicatus being considerably smaller than Ips typographus (Olenici et al. 2009), thus the surface area for attachment being reduced, particularly disadvantaging species that do not have specialized organs for attachment to the phoront or those that are larger, such as Pleuronectocelaeno austriaca (Moser et al. 1989a). 4.4 Localization of phoretic mites on the bodies of bark beetles The attachment of phoretic mites to the bodies of bark beetles generally occurs using the anal pedicel, chelicerae, or special mouthpieces for attachment (Bartlow and Agosta 2021). The distribution of phoretic mites is not random; certain areas of the host's body are chosen based on the phoretic species (Houck and O'Connor 1991), as well as the possibility of being removed from the host's body (Cejka and Holusa 2014). Many studies that have examined this stage of the phoretic relationship have shown that the most prone areas for phoretic mite attachment to the host's body are under the elytra, followed by the thorax and abdomen (Cilbircioğlu et al. 2021; Gwiazdowicz et al. 2015; Manu et al. 2017; Moser and Bogenschuütz 1984; Moser et al. 1989a; Paraschiv et al. 2018; Paraschiv and Isaia 2020; Poliță et al. 2016). These results somewhat align with those obtained in this study, where most phoretic mites were identified on the bodies of Ips typographus beetles under the elytra, followed by the thorax, abdomen, elytra, and abdomen, while in the case of Ips duplicatus beetles, they were found under the elytra, followed by the abdomen, thorax, and legs. The reason that the area under the elytra was the most phoretic in both species is due to the large number of Dendrolaelaps quadrisetus individuals predominantly found in this area of the body (Khaustov et al. 2018). Species such as Trichouropoda polytricha and Uroobovella ipidis attach to the host's body using the anal pedicel in the thorax or abdomen area (Moser and Bogenschuütz 1984). However, this preference can be affected by intra- and interspecific competition, leading mites to choose other parts of the body (Paraschiv and Isaia 2020). This is evidenced in the observations of this study, where Uroobovella ipidis was identified on the thorax, followed by the abdomen in the case of Ips duplicatus beetles, and on the first pair of legs in the case of Ips typographus beetles. Histiostoma piceae does not have a specific preference for a particular attachment site on the host's body (Khaustov et al. 2018); however, observations made in this study indicate a preference for the thorax of the hosts. An interesting aspect is that this species has been documented as having a hyperphoretic behavior with Uroobovella ipidis mites (Khaustov et al. 2016). In this study, hyperphoretic behavior was observed with individuals of the Dendrolaelaps quadrisetus species, which may explains the results of other studies that identified Histiostoma piceae predominantly under the elytra (Moser and Bogenschuütz 1984; Paraschiv and Isaia 2020). In the case of Ips typographus beetles, the Elattoma sp. mites did not show a specific preference, while for Ips duplicatus beetles, they were found between the first and second pairs of legs on the thorax or abdomen. This behavior aligns with the observations made by Khaustov et al. (2018). Paraleius leontonychus uses its claws to attach to the bodies of its hosts (Ahadiyat and Akrami 2015; Penttinen et al. 2013), which may be a reason for its lack of preference in attaching to the host's body. The size of Pleuronectocelaeno austriaca individuals, which makes it difficult to attach to a phoront, could explain why most specimens of this species were found under the elytra, a behavior also reported in other studies of species in this genus (Cilbircioğlu et al. 2021; Pernek et al. 2012). The fact that Proctolaelaps fiseri did not show a preference for attachment is supported by the results of other studies (Khaustov et al. 2018; Paraschiv and Isaia 2020). 5. Conclusions In this study, the populations of phoretic mites associated with two species of bark beetles were analyzed, the native species Ips typographus and the invasive species Ips duplicatus . The comparative analysis between the phoretic mite populations of these two bark beetle species highlighted considerable differences in terms of the rate of phoresy, the dynamics of the phoresy rate, as well as the structure and abundance of the two communities. The distribution of mites on the host bodies varied depending on the mite species and the abundance of mites on the hosts. Among the 9 species of phoretic mites identified in this study, 3 are reported for the first time in Romania: Dendrolaelaps disetus , Elattoma sp., and Paraleius leontonychus . Although both the phoresy rate and its dynamics varied between the two hosts throughout the vegetation season, the maximum phoresy for both bark beetle species was reached at the beginning of the flight of the hibernating generation, indicating this as the most important moment for the dissemination of mites into new habitats. The most abundant species on the bodies of Ips typographus beetles was Dendrolaelaps quadrisetus , which accounted for over half of the entire population. In the case of Ips duplicatus bark beetles, the population was dominated by specimens of Dendrolaelaps quadrisetus and Elattoma sp., with the latter being the only species exhibiting this behavior in host selection. Declarations Author Contribution D.T. Investigation, Methodology, Entomological material analyzed, Formal analysis, Writing - oroginal draft; G.I. Conceptualization, Methodology, Writing– review & editing; M.M. Entomological material analyzed; Writing– review & editing; D.S. Conceptualization, Supervision, Writing– review & editing Acknowledgments: This research was funded by PN 23090102, funded by the Ministry of Research, Innovation and Digitalization of Romania and in the frame of the project number RO1567-IBB01/2025, Institute of Biology Bucharest, Romanian Academy. The authors are grateful to all students from the Faculty of Silviculture and Forest Engineering Brașov for their voluntary help in collecting the field data. References Ahadiyat A, Akrami MA (2015) Oribatid mite (Acari: Oribatida) associated with bark beetles (Coleoptera: Curculionidae: Scolytinae) in Iran, with a review on Paraleius leontonychus (Berlese) and a list of bark beetles in association with this species. 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Current Biology 27(12):578-580. https://doi.org/10.1016/j.cub.2017.03.073 Wirth SF, Weis O, Pernek M (2016) Comparison of phoretic mites associated with bark beetles Ips typographus and Ips cembrae from central Croatia. Šumarski list 140(11-12):549-560. https://doi.org/10.31298/sl.140.11-12.2 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 25 Aug, 2025 Read the published version in Experimental and Applied Acarology → 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. 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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-6528419","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":451249473,"identity":"b77493ad-5130-4a80-86b4-6ebad12ad4cc","order_by":0,"name":"Dragoș Toma","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYDCCAwgm44MEUrRIADGzAcla2CSI0sF3+/DjFx/+MNTxix1+VvGgxs6eQfrwAbxaJM+lmVnObGOQkJydZnYj4VhyYgNfGn73GZxhMDPmbWCQMLidYHYjsYE5gYGHx4CAFvZvxjx/QFrSvxUkNtTbE6GFx/gxDxtIS44ZQ2LDYcYGQlokz/CUMc5sk5CcOTunWCLh2PHENh42/H7hO8O++cOHPzb8/NLpGz/+qKm25+dhPoBXCwMkOpBihI2QeiBg/kCEolEwCkbBKBjJAADYjkAoMF6QwAAAAABJRU5ErkJggg==","orcid":"","institution":"National Institute for Research and Development in Forestry \"Marin Drăcea\"","correspondingAuthor":true,"prefix":"","firstName":"Dragoș","middleName":"","lastName":"Toma","suffix":""},{"id":451249474,"identity":"f4b4c250-e3f6-4536-aac3-5d80e803b6f0","order_by":1,"name":"Gabriela Isaia","email":"","orcid":"","institution":"Transylvania University of Brașov","correspondingAuthor":false,"prefix":"","firstName":"Gabriela","middleName":"","lastName":"Isaia","suffix":""},{"id":451249475,"identity":"31c200f2-1704-4e54-8d8d-2435180b7492","order_by":2,"name":"Minodora Manu","email":"","orcid":"","institution":"Institute of Biology Bucharest of Romanian Academy","correspondingAuthor":false,"prefix":"","firstName":"Minodora","middleName":"","lastName":"Manu","suffix":""},{"id":451249476,"identity":"22c9c1bd-a0e3-46fb-b559-61702348fe1f","order_by":3,"name":"Carol Dieter Simon","email":"","orcid":"","institution":"Transylvania University of Brașov","correspondingAuthor":false,"prefix":"","firstName":"Carol","middleName":"Dieter","lastName":"Simon","suffix":""}],"badges":[],"createdAt":"2025-04-25 11:23:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6528419/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6528419/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10493-025-01053-3","type":"published","date":"2025-08-25T15:57:08+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82088890,"identity":"127df3f7-66ed-4ac0-bfa4-4b318c18c96c","added_by":"auto","created_at":"2025-05-06 15:43:37","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":200833,"visible":true,"origin":"","legend":"\u003cp\u003eLocation of the study area (Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, Aero Grid, IGN, and theGIS User Community)\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/676788151a5138f3e27c9788.jpeg"},{"id":82088889,"identity":"e68eedc9-2b06-4131-afd4-9b0bd921d593","added_by":"auto","created_at":"2025-05-06 15:43:37","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":98349,"visible":true,"origin":"","legend":"\u003cp\u003ePhoresy rate (±SE) and abundance dynamics of \u003cem\u003eIps typographus \u003c/em\u003e(\u003cstrong\u003ea\u003c/strong\u003e)\u003cem\u003e \u003c/em\u003eand \u003cem\u003eIps duplicatus \u003c/em\u003e(\u003cstrong\u003eb\u003c/strong\u003e) based on pheromone trap captures during the season.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/d3fe91a9066b9a5fefb0aaaf.jpg"},{"id":82088073,"identity":"1f6cfc95-1f2e-4d6b-a227-c77caafd5d07","added_by":"auto","created_at":"2025-05-06 15:35:37","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":431348,"visible":true,"origin":"","legend":"\u003cp\u003ePhoretic mites species indentified on \u003cem\u003eIps duplicatus \u003c/em\u003eand \u003cem\u003eIps typographus\u003c/em\u003e beetles: a. \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e; b. \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e; c. \u003cem\u003eElattoma sp.\u003c/em\u003e; d. \u003cem\u003eHistiostoma piceae\u003c/em\u003e; e. \u003cem\u003eParaleius leontonychus\u003c/em\u003e; f. \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e; g. \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e; h. \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e; i. \u003cem\u003eUroobovella ipidis\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/b4d4b17929ee813d559b139c.jpg"},{"id":82088887,"identity":"7e0cfcf0-7b02-4be3-b07a-7efabca49bf4","added_by":"auto","created_at":"2025-05-06 15:43:37","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34464,"visible":true,"origin":"","legend":"\u003cp\u003eNon-metric, multidimensional scaling (NMDS) of the two communities of phoretic mites represented as Bray-Curtis dissimilarity. PERMANOVA test with 9999 random permutations was used for the comparison.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/bf1e89a60ceab1cad70824cd.jpg"},{"id":82088888,"identity":"e9eedf1d-c220-46d6-8de1-5da7b26a3c50","added_by":"auto","created_at":"2025-05-06 15:43:37","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":103215,"visible":true,"origin":"","legend":"\u003cp\u003ePlace of attachment of phoretic mites on the body of \u003cem\u003eIps typographus \u003c/em\u003e(\u003cstrong\u003ea\u003c/strong\u003e) and \u003cem\u003eIps duplicatus \u003c/em\u003e(\u003cstrong\u003eb\u003c/strong\u003e)\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/f25d02e1d668ec6ee8a4898a.jpg"},{"id":82088067,"identity":"2b3ce8c0-b5fd-4594-93cc-34a6b9a5e251","added_by":"auto","created_at":"2025-05-06 15:35:37","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":14726,"visible":true,"origin":"","legend":"\u003cp\u003eThe hyperphoretic relationship between \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e (A) and \u003cem\u003eHistiostoma piceae \u003c/em\u003e(B)\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/7d041db0a76fc676d4a9506c.jpg"},{"id":90344921,"identity":"7c4dbcbd-d4eb-4188-8e50-4d2c8ab1bf2f","added_by":"auto","created_at":"2025-09-01 16:07:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2225672,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6528419/v1/4c2f3ac7-c170-43f5-8312-74680baef79a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Phoretic mite communities associated with Ips typographus (Linnaeus, 1758) and Ips duplicatus (Sahlber, 1836) (Coleoptera: Scolytinae) in a Norway spruce stand","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eNorway spruce (\u003cem\u003ePicea abies\u003c/em\u003e (L.) H. Karst) is considered the most important gymnosperm species in Europe (Caudullo et al. 2016; Skr\u0026oslash;ppa 2003; Westin and Haapanen 2013), covering an area of approximately 30\u0026nbsp;million hectares (Jansson et al. 2013). In Romania, it is the second most widespread tree species (Șofletea and Curtu 2008), where, both in pure and mixed forests, it occupies around 28% of the country's forested area (Sidor et al. 2015). Considering its ecological and especially economic importance, due to the exceptional quality of its wood (Caudullo et al. 2016; Westin and Haapanen 2013), the range of Norway spruce has been expanded over the past two centuries through artificial plantations outside its natural ranges (Caudullo et al. 2016; Jansson et al. 2013; Nețoiu et al. 2008), in areas characteristic of deciduous species (Jansson et al. 2013; Klimo et al. 2000).\u003c/p\u003e \u003cp\u003eAbiotic factors such as severe storms or extreme drought weaken and physiologically impair Norway spruce stands, particularly those outside their natural range (Caudullo et al. 2016; Spiecker 2000), thus creating favorable conditions for the outbreaks of bark beetles (Caudullo et al. 2016; Simionescu et al. 2000; Wermelinger 2004). The most destructive and aggressive pest among the bark beetles of Norway spruce is the European spruce bark beetle, \u003cem\u003eIps typographus\u003c/em\u003e (Linne 1758) (Caudullo et al. 2016; Marini et al. 2013; Netherer et al. 2019; Simionescu et al. 2000; Wermelinger 2004). Considered to be a species that normally colonizes dead or dying trees, during mass outbreaks it can also attack healthy trees (Simionescu et al. 2000; Wermelinger 2004; Weslien et al. 1989). In the past century, \u003cem\u003eI. typographus\u003c/em\u003e outbreaks have led to the partial or total dieback of millions of cubic meters of spruce trees in Europe (Gr\u0026eacute;goire and Evans 2004).\u003c/p\u003e \u003cp\u003eRecently, \u003cem\u003eIps duplicatus\u003c/em\u003e (Sahlberg 1836), another bark beetle species of conifers, has expanded its range (Olenici et al. 2009, 2022; Wermelinger et al. 2020), being considered an invasive species in Europe (Olenici et al. 2022; Z\u0026uacute;brik et al. 2006) and introduced in quarantine list by the European Union (Holuša et al. 2012). Although it attacks several species within the genus \u003cem\u003ePicea\u003c/em\u003e and occasionally \u003cem\u003ePinus\u003c/em\u003e, \u003cem\u003eLarix\u003c/em\u003e, and \u003cem\u003ePseudotsuga\u003c/em\u003e (Duduman et al. 2013; Kaš\u0026aacute;k and Foit 2015; Pfeffer and Kn\u0026iacute;žek 1995; Wermelinger et al. 2020), it prefers Norway spruce stands, particularly those outside their natural range (Olenici et al. 2009, 2022; Wermelinger et al. 2020), where it causes outbreaks of varying intensity (Grodzki 2003; Holuša et al. 2003; Olenici et al. 2009, 2011). Sometimes, the attack of \u003cem\u003eI. duplicatus\u003c/em\u003e on Norway spruce trees occurs together with \u003cem\u003eI. typographus\u003c/em\u003e (Grodzki 2012), as the species share similar behavior and biology (Wermelinger et al. 2020). In Romania, \u003cem\u003eIps duplicatus\u003c/em\u003e is now present in the vast majority of Norway spruce cultivation areas (Olenici et al. 20022).\u003c/p\u003e \u003cp\u003eTree dieback in outbreak areas is not only the result of bark beetle attacks but also of pathogenic fungi with which the beetles associate and introduce into the wood (Lieutier 2002; Linnakoski et al. 2016; Moser et al. 2010; Paine et al. 1997; Wermelinger 2004). \u003cem\u003eI. typographus\u003c/em\u003e is considered the bark beetle species most commonly associated with pathogenic fungi (Krokene and Solheim 1996). Numerous studies have shown that, in addition to pathogenic fungi, bark beetle populations are closely linked to other organisms such as nematodes or mites (Forsse 1987; Hofstetter et al. 2015; Moser and Bogensch\u0026uuml;tz 1984). Mite species, due to their lack of specialized legs for traveling long distances, use bark beetles for dispersal through a phenomenon called phoresy (Bartlow and Agosta 2021; Camerik 2010; White et al. 2017). These mites mainly belong to the orders Mesostigmata and Trombidiformes (Moser and Roton 1971; Moser 1985; Vissa and Hofstetter 2017). For dispersal to occur, phoresy must include three fundamental stages: host location, attachment to the host, and detachment at the appropriate time (Bartlow and Agosta 2021). Phoresy does not involve parasitic relationships, although it can become antagonistic to host species over time. A large number of phoretic organisms attached to the host body can somewhat affect the host's locomotion ability (Gwiazdowicz et al. 2011). Moreover, when a phoretic relationship forms between two organisms, it can evolve into a parasitic relationship (White et al. 2017).\u003c/p\u003e \u003cp\u003eIn the case of \u003cem\u003eIps typographus\u003c/em\u003e, following the significant outbreaks it caused in Norway spruce stands across Europe (Bakke 1983; Simionescu et al. 2000; Wermelinger 2004), interest in this pest has grown considerably, leading to intensive studies on the relationship between bark beetle populations and their phoretic mites. To date, numerous studies have focused on this aspect, with over 60 species of phoretic mites being identified in close association with the European spruce bark beetle, \u003cem\u003eI. typographus\u003c/em\u003e (Gwiazdowicz 2008; Skorupski and Gwiazdowicz 1998). On the other hand, the phoretic mite species, their abundance, and the relationship they have with the bark beetle \u003cem\u003eIps duplicatus\u003c/em\u003e have been very little studied, with only one study conducted in Europe so far (Čejka and Holuša 2014). Furthermore, a comparative analysis of the phoretic mite populations associated with the two bark beetle species, which coexist and jointly attack trees in an outbreak, has not been conducted.\u003c/p\u003e \u003cp\u003eIn this context, through this study, we aim to determine and analyze the following aspects: (i) the populations of phoretic mites associated with \u003cem\u003eIps typographus\u003c/em\u003e and \u003cem\u003eIps duplicatus\u003c/em\u003e; (ii) the attachment preference of phoretic mite species based on their host; (iii) the dynamic of the phoresy of the two bark beetle species throughout the entire growing season; (iv) comparative analysis of phoretic mite populations based on their host.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Study area\u003c/h2\u003e \u003cp\u003eThe research was conducted in a Norway spruce stand near R\u0026acirc;șnov (45\u0026deg;35 N; 25\u0026deg;28 E), Brașov County, managed by the R\u0026acirc;șnov Town Forest Administration, in forest compartment 72B (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The stand is 80 years old and it is situated at an altitude of 715 m, at the lower limit of the Norway spruce range. \u003cem\u003eIps duplicatus\u003c/em\u003e has been reported in this area since 2011 (Duduman et al. 211).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Collection and analysis of entomological material\u003c/h2\u003e \u003cp\u003eBark beetles were collected using six intercept traps (wing type), three baited with a commercial pheromone AtraTYP specific to \u003cem\u003eIps typographus\u003c/em\u003e and three baited with a commercial pheromone AtraDUP specific to \u003cem\u003eIps duplicatus\u003c/em\u003e, both produced by the Raluca Ripan Institute of Chemistry, Romania. The distance between the two trap arrays was 25 m, while the distance between traps within the arrays was 50 m. The traps were set up on May 2, 2023, at 10\u0026ndash;12 m from the forest edge, and bark beetles were collected every 7\u0026ndash;11 days throughout the entire growing season, with the last collection in mid-September.\u003c/p\u003e \u003cp\u003eThe collected beetles were stored in a freezer at a temperature of -5\u0026deg;C to prevent the detachment of phoretic mites from their hosts (Moser and Bogenschu\u0026uuml;tz 1984; Paraschiv and Isaia 2020). Subsequently, from each capture, the bark beetles were identified, and a sample of 50 specimens was retained for the analysis of phoretic mites. If the number of bark beetles per trap was less than 50 specimens, all available specimens were analyzed (Blaženec and Jakuš 2009; Paraschiv and Isaia 2020). Insect sex determination was performed through dissection based on their genitalia (Duduman et al. 2019, 2022). Regarding the phoretic mites on the bodies of the beetles, after the species identification their numbers were recorded based on the location of attachment to the beetle bodies. The mite species were identified using identification keys provided by the scientific literature (Ghiliarov and Bregetova 1977; Kinn 1968; Khaustov 2000; Moser and Bogenschu\u0026uuml;tz 1984; Rahiminejad et al. 2011, Trach and Khustov 2018). To determine the attachment preference of the phoretic mites to their hosts, the bodies of the bark beetles were subdivided into several parts: head, thorax, abdomen, first, second and third pair of legs, elytral declivity, and under elytra (Paraschiv and Isaia 2020). Beetle sex determination was performed using a stereomicroscope. The taxonomical identification/cheking of the phoretic mites was performed using a Zeiss Axio Scope A 1 microscope. Photos of the phoretic mite species identified in this study were taken with a CX43 microscope equipped with a Promicam Lite Digital Camera. Voucher specimens of all mite species detected in this study are stored at the laboratory of the \"Marin Drăcea\" National Institute for Research and Development in Forestry, Voluntari, Ilfov.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Statistical Analysis\u003c/h2\u003e \u003cp\u003eThe zoocenological analysis of mite communities was evaluated using the dominance index (D), categorized as follows: eudominant (\u0026gt;\u0026thinsp;30%), dominant (15.01\u0026ndash;30%), sub-dominant (7.01\u0026ndash;15%), resident (3.01\u0026ndash;7%), and sub-resident (\u0026lt;\u0026thinsp;3%); and frequency (F) with the following classes: euconstant (\u0026gt;\u0026thinsp;50%), constant (30.01\u0026ndash;50%), subconstant (15.01\u0026ndash;30%), accessory species (5.01\u0026ndash;15%), and accidental occurrence (\u0026lt;\u0026thinsp;5%), as used in other studies (Gwiazdowicz et al. 2011; Paraschiv and Isaia 2020). Dominance (D) was calculated by dividing the total number of individuals of a phoretic mite species by the total number of phoretic mites. Frequency (F) was determined as the ratio of the total number of bark beetle with a specific species of phoretic mites to the total number of analyzed beetles. Phoresy rate was determind by the ratio between beetles that carried mites and total number of beetles analyzed.\u003c/p\u003e \u003cp\u003eThe application of the Shapiro-Wilk test confirmed the normal distribution of the data, and Levene's test verified the homogeneity of the data, thus meeting the requirements for the application of parametric tests. In order to evaluate if the intensity of phoresy and the phoresy rate were influenced by factors such as bark beetle species, collection date or beetle sex, and to determine the most phorezed body parts of the each bark beetle species and the attachment preference of each mite species for a specific body part of their hosts, One-Way ANOVA analysis of variance was conducted. The significance level of the differences between variables was established using Tukey's multiple test. Due to the low number of attached phoretic mites the attachment on the first, second and third pair of legs and the head in the case of \u003cem\u003eIps typographus\u003c/em\u003e and the attaachment on the head and the third pair of legs in the case of \u003cem\u003eIps duplicatus\u003c/em\u003e were not included in the statistical analyses. If the number of specimens for a species was insufficient for this analysis, or if individuals of a species did not exhibit a specific preference for any particular body part, it was noted that the species had no distinct attachment preference.\u003c/p\u003e \u003cp\u003eThe characterization and evaluation of the differences between the phoretic mite populations of the two bark beetle species were determined using diversity indices such as the Shannon diversity index (H\u0026rsquo;), Simpson index (1-D), Evenness index (e^H/S), and Berger-Parker index, along with the PERMANOVA test (Anderson 2014; Isaia et al. 2022; Magurran 2004). The application of the PERMANOVA test on the two communities was conducted based on Bray-Curtis dissimilarity and 9999 random permutations. To ensure that the effect of the dominant species (\u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e Berlese 1920) did not overly influence the analysis results, the data were transformed using the log10(x\u0026thinsp;+\u0026thinsp;1) function (Isaia et al. 2022). To visualize the differences between the phoretic mite assemblage populations of the two bark beetle species, non-metric multidimensional scaling (NMDS) was employed (Revainera et al. 2019).\u003c/p\u003e \u003cp\u003eFor the primary data processing and graphical presentation of the dynamics of the phoretic rate in relation to the capture levels of the two bark beetle species, Microsoft Excel (Microsoft Corp., Redmond, Washington, USA) was used. Normality testing, homogeneity, and statistical differences were performed using STATISTICA 8.0 software (Wei\u0026szlig; 2007). The diversity indices, PERMANOVA test, and NMDS were conducted with PAST 4.03 (Hammer and Harper 2001).\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. The dynamics of insect flight and phoresy rates\u003c/h2\u003e\n \u003cp\u003eDuring the entire vegetation season, a total of 55,276 bark beetles were captured in the pheromone traps, 51,222 of them were \u003cem\u003eI. typographus\u003c/em\u003e and 4,054 were \u003cem\u003eI. duplicatus\u003c/em\u003e. The two species reached their peak flight intensity at different times. For \u003cem\u003eI. typographus\u003c/em\u003e, the highest number of beetles was recorded in the second decade of May, while for \u003cem\u003eI. duplicatus\u003c/em\u003e, the highest number of beetles was recorded in the first decade of July.\u003c/p\u003e\n \u003cp\u003eOut of the total captured beetles, 2,413 specimens of \u003cem\u003eI. typographus\u003c/em\u003e were subsequently analyzed to determine the phoretic mites, resulting a phoresy rate of 49.3%. For \u003cem\u003eI. duplicatus\u003c/em\u003e, 1,935 beetles were analyzed, of which only 20.6% carried phoretic mites on their bodies. The differences between the two species were significant (df\u0026thinsp;=\u0026thinsp;1, f\u0026thinsp;=\u0026thinsp;133.8, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Both \u003cem\u003eI. typographus\u003c/em\u003e males (50.71%) and I. \u003cem\u003eduplicatus\u003c/em\u003e males (23.38%) were more phorezed than females (47.95%; 17.86%), but there were no significant differences (df\u0026thinsp;=\u0026thinsp;1, f\u0026thinsp;=\u0026thinsp;0.737, p\u0026thinsp;\u0026gt;\u0026thinsp;0.05; df\u0026thinsp;=\u0026thinsp;1, f\u0026thinsp;=\u0026thinsp;2.09, p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n \u003cp\u003eRegarding the dynamics of phoresy rates over time, significant fluctuations were observed for both \u003cem\u003eI. typographus\u003c/em\u003e (df\u0026thinsp;=\u0026thinsp;17, f\u0026thinsp;=\u0026thinsp;5.195, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and \u003cem\u003eI. duplicatus\u003c/em\u003e (df\u0026thinsp;=\u0026thinsp;17, f\u0026thinsp;=\u0026thinsp;4.7542, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). For \u003cem\u003eI. typographus\u003c/em\u003e (Fig. 2a), the phoresy rate reached its first peak at the beginning of the flight (May 9 \u0026ndash; May 16), followed by two more peaks at the beginning of August (August 3 \u0026ndash; August 10) and at the end of the flight (August 28 \u0026ndash; September 3). Although at a considerably lower intensity, the phoresy rate for \u003cem\u003eI. duplicatus\u003c/em\u003e exhibited peaks similar to those recorded for \u003cem\u003eI. typographus\u003c/em\u003e (Fig. 2b). The first and most significant peak \u003cem\u003efor I. duplicatus\u003c/em\u003e was recorded at the beginning of the flight (May 9 \u0026ndash; May 16), followed by two additional peaks at the end of July (July 20 \u0026ndash; July 27) and at the end of the flight (August 28 \u0026ndash; September 3). Interestingly, the lowest of phoresy rates recorded for \u003cem\u003eI. typographus\u003c/em\u003e was close in values to the peaks of phoresy rates of \u003cem\u003eI. duplicatus\u003c/em\u003e, as a result of the phoretic load between the two species.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Species composition and zoocenological analysis\u003c/h2\u003e\n \u003cp\u003eThe phoretic mites identified on the body of \u003cem\u003eIps typographus\u003c/em\u003e belong to nine species, namely: \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e (Berlese 1920), \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e (Hirschmann 1960), \u003cem\u003eElattoma\u003c/em\u003e sp., \u003cem\u003eHistiostoma piceae\u003c/em\u003e (Scheucher 1957), \u003cem\u003eParaleius leontonychus\u003c/em\u003e (Berlese 1910), \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e (Vitzthum 1926), \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e (Samsinak 1960), \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e (Vitzthum 1923), and \u003cem\u003eUroobovella ipidis\u003c/em\u003e (Vitzthum 1923) (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The most frequent and dominant species on the bodies of \u003cem\u003eI. typographus\u003c/em\u003e beetles was \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e, which represented more than half of the total (63.46%). Specimens of this species, along with specimens of the species \u003cem\u003eUroobovella ipidis\u003c/em\u003e, \u003cem\u003eHistiostoma piceae\u003c/em\u003e, and \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e, accounted for a total of 98% of the entire mite population, while the other species were classified as having accidental dominance and accidental occurrence frequency.\u003c/p\u003e\n \u003cp\u003eOnly six species of mites were found on the bodies of \u003cem\u003eI. duplicatus\u003c/em\u003e beetles, with their dominance being more evenly distributed compared to \u003cem\u003eI. typographus\u003c/em\u003e (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Although \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e was one of the most dominant and frequent species, it was not the most abundant; that position was held by the genus \u003cem\u003eElattoma\u003c/em\u003e. \u003cem\u003eElattoma\u003c/em\u003e sp., \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e and \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e represented approximately 86% of the total mite population in the case of \u003cem\u003eI. duplicatus\u003c/em\u003e. The frequency of the mite species identified on \u003cem\u003eI. duplicatus\u003c/em\u003e was much lower, not exceeding 10% for any of the species. The species \u003cem\u003eElattoma\u003c/em\u003e sp. was the only species that was more abundant on the \u003cem\u003eIps duplicatus\u003c/em\u003e beetles compared to the \u003cem\u003eIps typographus\u003c/em\u003e beetles.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePhoretic mite species of \u003cem\u003eIps typographus\u003c/em\u003e and \u003cem\u003eIps duplicatus\u003c/em\u003e, their dominance, frequency and feeding behavior.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"9\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFamily\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFeeding\u003c/p\u003e\n \u003cp\u003eBehavior\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cem\u003eIps typographus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cem\u003eIps duplicatus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbundance\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDominance (%)\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFrequency (%)\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbundance\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDominance (%)\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFrequency (%)\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDigamasellidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDendrolaelaps quadrisetus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePredacious\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1963\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63.46 eudominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.29 constant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e186\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.85 eudominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.6 accesory species\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDigamasellidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDendrolaelaps disetus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePredacious\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.07 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.08 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePygmephoridae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eElattoma\u003c/strong\u003e \u003cstrong\u003esp.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMycetophagous\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.16 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.2 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e197\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.73 eudominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.58 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHistiostomatidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eHistiostoma piceae\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnknown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e376\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.28\u003c/p\u003e\n \u003cp\u003esub-dominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.15 accessory species\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.62 sub-dominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.32 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOribatulidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eParaleius leontonychus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnknown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.36 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNeotenogyniidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePleuronectocelaeno austriaca\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePredacious\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.29 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.33 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMelicharidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eProctolaelaps fiseri\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePredacious\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.88 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.95 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTrematuridae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTrichouropoda polytricha\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnknown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.73\u003c/p\u003e\n \u003cp\u003esub-dominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.15 accessory species\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e121\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.72 dominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.55 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUrodinychidae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eUroobovella ipidis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnknown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e391\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.77\u003c/p\u003e\n \u003cp\u003esub-dominant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.31 accessory species\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.91 accidental\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.77 accidental occurrence\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"9\"\u003e\u003csup\u003e\u003cstrong\u003ea\u003c/strong\u003e\u003c/sup\u003e According to Hofstetter et al. (2014)\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"9\"\u003e\u003csup\u003e\u003cstrong\u003eb\u003c/strong\u003e\u003c/sup\u003e Classification according to Gwiazdowicz et al. (2011)\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Community diversity and structure\u003c/h2\u003e\n \u003cp\u003eThe diversity indices show significant differences between the two analyzed communities of phoretic mites (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). In the case of the Shannon (H), Simpson, and Evenness indices, the results indicate that the phoretic mite community associated with the bark beetle \u003cem\u003eI. duplicatus\u003c/em\u003e is more diverse and uniformly distributed. The considerably higher value recorded for the Berger-Parker index in the phoretic mite community of \u003cem\u003eI. typographus\u003c/em\u003e indicates that it was dominated by a single species.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDiversity indices of the two community\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDiversity index\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eIps typographus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eIps duplicatus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eShannon_H\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.409\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eEvenness_e^H/S\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.344\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.682\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSimpson_1-D\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5564\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.7297\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eBerger-Parker\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.6346\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3373\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe result of the permutational analysis of variance (PERMANOVA) indicates a significant difference in the composition of the phoretic mite communities associated with the two bark beetle species (F\u0026thinsp;=\u0026thinsp;30.58, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The NMDS analysis shows that, although the two populations do not completely differentiate from each other, the community associated with the bark beetle \u003cem\u003eIps typographus\u003c/em\u003e is much more centered, showing a tendency to separate from the community of \u003cem\u003eIps duplicatus\u003c/em\u003e (Fig. 3). The low stress level of the NMDS plot (0.14) indicates a good fit of the distances between points, making it a valid representation of the composition of the two phoretic mite communities (Magurran 2004).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4. Location of phoretic mites on the bodies of bark beetles\u003c/h2\u003e\n \u003cp\u003eSignificant differences were recorded between the average number of phoretic mites attached to different body parts for both bark beetle species. For \u003cem\u003eIps typographus\u003c/em\u003e, the highest average number of mites was recorded under the elytra (1.85), significantly differing from the other parts (df\u0026thinsp;=\u0026thinsp;4, f\u0026thinsp;=\u0026thinsp;38.44, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05): thorax (0.33), elytral declivity (0.27), elytra (0.27), and abdomen (0.23) (Fig. 5a). In the case of \u003cem\u003eIps duplicatus\u003c/em\u003e, the highest average number of mites was also found under the elytra (0.33), significantly differing from the other parts (df\u0026thinsp;=\u0026thinsp;6, f\u0026thinsp;=\u0026thinsp;10.43, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig. 5b). The next preferred attachment sites were the elytral declivity (0.19), abdomen (0.17), and the thorax (0.16). Although the average number of phoretic mites differs between the two hosts, the results regarding the localization of mites on their bodies are similar, with the majority of mites located under the elytra in both species, followed by the thorax, abdomen, pairs of legs, and elytra. Additionally, the less frequented areas for mites were the heads of the hosts and pairs of legs 3 in both species of bark beetles.\u003c/p\u003e\n \u003cp\u003eThe distribution of phoretic mites on host bodies is not random; it varies depending on the host species and the species of phoretic mites. For both \u003cem\u003eIps duplicatus\u003c/em\u003e and \u003cem\u003eIps typographus\u003c/em\u003e, the majority of specimens of \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e were identified under the hosts\u0026apos; elytra, with the differences statistically supported by the other locations (DF 8; F 52.31; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05; DF 8; F 44.93; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Although the few specimens of \u003cem\u003eElattoma\u003c/em\u003e sp. detected on \u003cem\u003eIps typographus\u003c/em\u003e did not show a preference for any specific body part, those identified on \u003cem\u003eIps duplicatus\u003c/em\u003e were mainly located in the area between pairs of legs 1 and 2, on the abdomen or thorax, significantly differing (DF 8; F 4.772; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) from the rest of the body parts.\u003c/p\u003e\n \u003cp\u003eNotable differences in attachment between the two hosts were also observed for the species \u003cem\u003eHistiostoma piceae\u003c/em\u003e, \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e, and \u003cem\u003eUroobovella ipidis\u003c/em\u003e. However, it is worth noting a particular behavior in some specimens of \u003cem\u003eHistiostoma piceae\u003c/em\u003e located under the hosts\u0026rsquo; elytra in hyperphoresis with some specimens of \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). The only specimen of \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e identified on \u003cem\u003eIps duplicatus\u003c/em\u003e was found on the abdomen, whereas specimens identified on \u003cem\u003eIps typographus\u003c/em\u003e did not show a specific preference, with most located under and on the elytra (DF 8; F 1.376; p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The attachment preference of the species \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e on \u003cem\u003eIps typographus\u003c/em\u003e was predominantly under the elytra (DF 8; F 3.224; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). \u003cem\u003eParaleius leontonychus\u003c/em\u003e did not show a significant preference for the host body (DF 8; F 0.996; p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The only two specimens of \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e were identified on the thorax of \u003cem\u003eIps typographus\u003c/em\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\" class=\"fr-table-selection-hover\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMain location of mites on the hosts body\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDistribution of mites on the body of\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eIps duplicatus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDistribution of mites on the body of\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eIps typographus\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"1\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLocation\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eProportion of total mites (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLocation\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eProportion of total mites (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDendrolaelaps quadrisetus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnder elytra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnder elytra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDendrolaelaps disetus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eElattoma\u003c/strong\u003e \u003cstrong\u003esp\u003c/strong\u003e.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdomen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\" rowspan=\"2\"\u003e\n \u003cp\u003eDid not not show a preference\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eHistiostoma piceae\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdomen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eElytra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdomen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eParaleius leontonychus\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDid not not show a preference\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePleuronectocelaeno\u003c/strong\u003e \u003cstrong\u003eaustriaca\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eUnder elytra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eProctolaelaps fiseri\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdomen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eDid not not show a preference\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eTrichouropoda polytricha\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eElytral declivity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eElytral declivity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eUroobovella ipidis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThorax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbdomen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePairs of legs 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.1. The dynamics of insect flight and phoretic rates\u003c/h2\u003e \u003cp\u003eFrom its first report in Romania in the mid-20th century (Negru and Ceianu 1957) until now, the northern bark beetle \u003cem\u003eIps duplicatus\u003c/em\u003e has become a commonly encountered species in Romania, particularly in spruce forests outside its natural range (Olenici et al. 2022). In the sample area where this study was conducted, this pest was reported for the first time in 2011 (Duduman et al. 2011). Several studies indicate that \u003cem\u003eIps duplicatus\u003c/em\u003e is a secondary pest that primarily colonizes trees aged between 30 and 70 years in the upper part of the crown, where the bark is thinner (Bakke 1975; Lekander et al. 1977; Postner 1974). The secondary character of this pest is also reflected in our study's results, where captures recorded for \u003cem\u003eIps typographus\u003c/em\u003e are significantly higher than those for the northern bark beetle. The advanced age of the trees in the sample area does not suit the preferences of \u003cem\u003eIps duplicatus\u003c/em\u003e, thereby maintaining the population at a low level. The fact that \u003cem\u003eIps typographus\u003c/em\u003e was the dominant species may also explain the preference of phoretic mites in choosing hosts for transportation to other habitats. The rate of phoresy for \u003cem\u003eIps typographus\u003c/em\u003e beetles varied between 29% and 65%, with an average of 49.3%, representing the highest phoresy rate recorded in Romania (Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016) and in Europe (Gwiazdowicz et al. 2011, 2012; Zach et al. 2016; Milosavljević et al. 2022; Moser and Bogenschu\u0026uuml;tz 1984; Moser et al. 1989a; Takov et al. 2009). These differences in results from studies conducted to date can be explained in various ways, starting from the method of preserving the bark beetles up to the moment of their analysis. In the case of beetles preserved in alcohol (ethanol), there is a risk that some phoretic mites may detach (Moser and Bogenschu\u0026uuml;tz 1984), which is the main reason why the beetles collected during the study were stored as quickly as possible at negative temperatures in freezers. Additionally, other factors that could influence the capture rate of phoretic mites might include the age of the bark beetle outbreak (Peralta V\u0026aacute;zquez 2018), the dynamics and density of the host beetle population (Paraschiv and Isaia 2020), or the location where the beetles overwinters, with those overwintering in the litter having lower chances of being phoresed by mites (Annila 1969). These hypotheses may explain why \u003cem\u003eIps duplicatus\u003c/em\u003e beetles were significantly less phoresed than \u003cem\u003eIps typographus\u003c/em\u003e. The phoresy rate of phoretic mites on \u003cem\u003eIps duplicatus\u003c/em\u003e beetles varied from 3\u0026ndash;45%, with an average of 20.6%. The fact that adult \u003cem\u003eIps duplicatus\u003c/em\u003e primarily overwinter in the litter (Olenici et al. 2009; Zhang 1995) may explain the low capture percentage of phoretic mites; however, from the results obtained (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), the highest percentages were reached at the beginning of the flight of the hibernating generation, although they did not reach the values of the hibernating generation of \u003cem\u003eIps typographus\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). The hypotheses suggesting that outbreak age, density, and population dynamics may influence the relationship between phoretic mites and bark beetles appear to be closer to the truth. Given that \u003cem\u003eIps duplicatus\u003c/em\u003e is a new species in the Romanian fauna and its presence in the study area was reported only in 2011, this may explain the low capture percentage. Furthermore, some species of mites might prefer individuals of the dominant species in the outbreak over other secondary species. In this context, the research conducted by Poliță et al. (2016), which analyzed the relationship between phoretic mites and bark beetles \u003cem\u003eIps typographus\u003c/em\u003e and \u003cem\u003ePityogenes chalcographus\u003c/em\u003e (Linnaeus, 1761) in spruce stands aged 80\u0026ndash;110 years, yielded similar results, with \u003cem\u003eIps typographus\u003c/em\u003e specimens being more phoresed than \u003cem\u003ePityogenes chalcographus\u003c/em\u003e. Additionally, another study analyzing the populations of phoretic mites associated with bark beetles of pine trees in Portugal showed that the specimens of the primary pest \u003cem\u003eIps sexdentatus\u003c/em\u003e (Boerner 1776) carried more mites than the specimens of the secondary pest \u003cem\u003eHylurgus ligniperda\u003c/em\u003e (Fabricius 1787) (Vissa et al. 2019).\u003c/p\u003e \u003cp\u003eAlthough the intensities varied between the two analyzed species, the percentages of phoretic mite captures on hosts peaked during similar periods. The first and most significant peak occurred at the beginning of the insect flight in the first decade of May, the second peak was reached in the second decade of July and early August, when the number of beetles caught in traps significantly decreased, and the last peak was observed at the end of August and the beginning of September, coinciding with the end of the adults' flight. The results obtained are similar with the research conducted by Paraschiv and Isaia (2020). Furthermore, their study indicates that most phoretic mites were transported by the hibernating generation of beetles and those from the second generation. Considering that both \u003cem\u003eIps typographus\u003c/em\u003e and \u003cem\u003eIps duplicatus\u003c/em\u003e typically have two generations per year in Romania (Olenici et al., 2009; Simionescu et al. 2000), this observation aligns with the results obtained in this study. Although phoretic mites did not show a preference for the sex of the beetles from either species, a finding confirmed in other studies (Paraschiv et al. 2018; Paraschiv and Isaia 2020), males transported more mites than females. This aspect may be due to the fact that males of both species come into contact with more females (Lubojack\u0026yacute; and Holuša 2013; Simionescu et al. 2000), thus increasing the probability that males will be phoresed. In this regard, a study conducted in Georgia on the pathogens of \u003cem\u003eIps typographus\u003c/em\u003e beetles found that males were more infested with a species of protozoan than females (Burjanadze and Goginashvili 2009).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.2. Species composition and zoocenological analysis\u003c/h2\u003e \u003cp\u003eThe total number of phoretic mite species identified in this study on \u003cem\u003eIps typographus\u003c/em\u003e is the highest reported in Romania compared to the other three studies conducted to date (Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016). This result is greater than or comparable to the findings from studies conducted in the Czech Republic (Čejka and Holuša 2014; Holuša and Čejka 2020), Turkey (Cilbircioğlu et al. 2021), Serbia (Milosavljević et al. 2022), Bulgaria (Takpv et al. 2009), Georgia (Burjanadze et al. 2008), Poland (Gwiazdowicz et al. 2011), Slovakia (Zach et al. 2016), and Croatia (Wirth et al. 2016), but considerably lower than the results from other studies conducted in Germany (Moser and Bogenschu\u0026uuml;tz 1984), Sweden (Moser et al. 1989a), Poland (Gwiazdowicz et al. 2012, 2015), and Finland (Penttinen et al. 2013). The differences between these results can be explained by the methods of preserving and storing entomological material (Paraschiv and Isaia 2020), the specifics of the area where the insects were collected, the total number of beetles analyzed (Gwiazdowicz et al. 2011), or the methods used for identifying mites, whether on the bodies of the insects or in their galleries. For example, a study conducted in Russia that analyzed mites associated with \u003cem\u003eIps typographus\u003c/em\u003e both on their bodies and from galleries identified over 60 species of phoretic mites closely linked to their hosts (Khaustov et al. 2018). The species identified in this study on the bodies of \u003cem\u003eIps typographus\u003c/em\u003e beetles are relatively common species also found in other studies, although three of them are reported for the first time in Romania: \u003cem\u003eParaleius leontonychus\u003c/em\u003e, \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e, and \u003cem\u003eElattoma\u003c/em\u003e sp.\u003c/p\u003e \u003cp\u003eThe most abundant and dominant species, \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e, has been found in Europe not only on \u003cem\u003eIps typographus\u003c/em\u003e (Moser and Bogenschu\u0026uuml;tz 1984; Penttinen et al. 2013; Takov et al. 2009) but also on specimens of \u003cem\u003eIps sexdentatus\u003c/em\u003e (Paraschiv et al. 2018; Vissa et al. 2019), \u003cem\u003ePityokteines curvidens\u003c/em\u003e (Pernek et al. 2012), \u003cem\u003ePityogenes chalcographus\u003c/em\u003e (Poliță et al. 2016), \u003cem\u003eIps duplicatus\u003c/em\u003e (Čejka and Holuša 2014), \u003cem\u003eOrthotomicus erosus\u003c/em\u003e (Vissa et al. 2019), \u003cem\u003eHylurgus ligniperda\u003c/em\u003e (Vissa et al. 2019), \u003cem\u003ePolygraphus polygraphus\u003c/em\u003e (Michalski et al. 1992), and \u003cem\u003eIps acuminatus\u003c/em\u003e (Cilbircioğlu et al. 2021). Furthermore, this species has also been found on various bark beetle species in North America, such as \u003cem\u003eIps pini\u003c/em\u003e, \u003cem\u003eDendroctonus frontalis\u003c/em\u003e, and \u003cem\u003eDendroctonus valens\u003c/em\u003e (Hofstetter et al. 2015). This species exhibits a generalist behavior regarding its phoretic host and inhabits a wide range of habitats (Moser 1996). The fact that this species was the most frequently encountered is not unexpected, as similar results have been reported in other studies (Gwiazdowicz et al. 2011, 2015; Holuša and Čejka 2020; Manu et al. 2017; Paraschiv and Isaia 2020; Poliță et al. 2016). On the contrary, the other species from the genus \u003cem\u003eDendrolaelaps\u003c/em\u003e identified in this study, \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e, is specific \u003cem\u003eto Ips typographus\u003c/em\u003e (Hofstetter et al. 2015) and has so far been found in Germany (Moser and Bogenschu\u0026uuml;tz 1984) and Poland (Skorupski and Gwiazdowicz 1998). Species from the genus \u003cem\u003eDendrolaelaps\u003c/em\u003e are predatory, typically feeding on small organisms found in the galleries of bark beetles (Kinn 1983). However, several studies indicate that \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e may also increase the mortality of bark beetles (Penttinen et al. 2013) by consuming their eggs and larvae (Khaustov et al. 2018; Maslov 2006; Pernek et al. 2008). Similar feeding behavior is exhibited by \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e and \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e. Like \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e, \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e is a generalist phoretic mite species, reported on several species of bark beetles (Hofstetter et al. 2015; Khaustov et al. 2018; Paraschiv and Isaia 2020) in various habitats across Eurasia and North America (Khaustov et al. 2018). The low number of specimens identified in this study aligns with results from other studies (Paraschiv and Isaia, 2020; Penttinen et al. 2013; Poliță et al. 2016), often being classified as a rare, accidental species. \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e has so far been found in association with \u003cem\u003eIps typographus\u003c/em\u003e (Hofstetter et al. 2015), \u003cem\u003eScolytus scolytus\u003c/em\u003e (Moser et al. 2010), and \u003cem\u003eScolytus laevis\u003c/em\u003e (Vitzthum 1926), having been reported in Romania (Manu et al. 2017), Poland (Gwiazdowicz et al. 2015), the Czech Republic (Holuša and Čejka 2020), and Austria (Moser et al. 2010; Vitzthum 1926). These reports may indicate that the range of this species is in Central and Eastern Europe. The low number of specimens may be attributed to the size of this phoretic mite species, which may obstract the attachment with the host (Moser et al., 1989a).\u003c/p\u003e \u003cp\u003eThe two species from the suborder Uropodina, namely \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e and \u003cem\u003eUroobovella ipidis\u003c/em\u003e, are commonly found in high abundance in several studies focusing on the phoretic mites associated with the bark beetle \u003cem\u003eIps typographus\u003c/em\u003e (Holuša and Čejka 2020; Khaustov et al. 2018; Manu et al. 2017; Moser et al. 1989a; Penttinen et al. 2013; Paraschiv and Isaia 2020; Takov et al. 2009), as well as other species of bark beetles (Hofstetter et al. 2015). The relationship between these two species and their hosts is unknown; they most likely use insects solely for transportation (Paraschiv and Isaia 2020). However, some studies suggest that species from the genera \u003cem\u003eTrichouropoda\u003c/em\u003e and \u003cem\u003eUroobovella\u003c/em\u003e may act as vectors for spores of fungi that alter wood color (Cardoza et al. 2008; Roets et al. 2014), and \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e could be a predator of nematodes in the galleries of bark beetles (Kinn 1982).\u003c/p\u003e \u003cp\u003e \u003cem\u003eHistiostoma piceae\u003c/em\u003e inhabits the galleries of a large number of bark beetles (Hofstetter et al. 2015; Pernek et al. 2008, 2012; Wirth et al. 2016) across Eurasia, showing a greater affinity for habitats rich in fungal spores (Hofstetter et al. 2013). Specimens of this species can be vectors for certain pathogenic fungi that significantly reduce the resistance of host trees, ultimately leading to their death (Moser et al. 1989a). Thus, the relationship between this species and bark beetles can be beneficial for both organisms involved in the phoretic process.\u003c/p\u003e \u003cp\u003eAlthough \u003cem\u003eParaleius leontonychus\u003c/em\u003e is most often found in low abundance (Cilbircioğlu et al. 2021; Moser and Bogenschu\u0026uuml;tz 1984; Pernek et al. 2008), it is a species with a wide distribution in the bark galleries of many insects (Ahadiyat and Akrami 2015). Its feeding behavior is unknown, although some authors suggest that it may be a detritivorous species (Penttinen et al. 2013; Pernek et al. 2008). Additionally, this species may act as a vector for pathogenic fungi (Moser et al. 1989b, 1997)\u003c/p\u003e \u003cp\u003eThe 12 species from the genus \u003cem\u003eElattoma\u003c/em\u003e known to date are considered mycetophagous, and some of them can transport spores of pathogenic fungi (Rahiminejad et al. 2011). These species form phoretic relationships with several bark beetles (Rahiminejad et al. 2011) but are considered as rare and infrequent (Moser et al. 1989a; Hofstetter et al. 2013). This observation aligns with the results obtained for \u003cem\u003eIps typographus\u003c/em\u003e beetles but not for \u003cem\u003eIps duplicatus\u003c/em\u003e, where specimens of the genus \u003cem\u003eElattoma\u003c/em\u003e were the most abundant, being, in fact, the only phoretic mite species that exhibited this preference. The only species from the genus \u003cem\u003eElattoma\u003c/em\u003e that forms phoretic relationships more with \u003cem\u003eIps duplicatus\u003c/em\u003e than with \u003cem\u003eIps typographus\u003c/em\u003e is \u003cem\u003eElattoma crossi\u003c/em\u003e (Khaustov et al. 2018). This species, which has been identified in the Siberian taiga (the native range of \u003cem\u003eIps duplicatus\u003c/em\u003e beetles), may have been introduced to Romania with the migration of the beetles towards Southeast Europe. However, since the species could not be accurately identified, this remains only a hypothesis.\u003c/p\u003e \u003cp\u003eThe only study that focused on identifying species of mites associated with \u003cem\u003eIps duplicatus\u003c/em\u003e, in Europe, identified only 3 species of phoretic mites on the bodies of the insects, namely \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e, \u003cem\u003eUroobovella ipidis\u003c/em\u003e, and \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e (Čejka and Holuša 2014), a significantly lower number compared to the 6 species identified in this study. However, it is worth mentioning that the study in the Czech Republic did not target \u003cem\u003eIps duplicatus\u003c/em\u003e beetles throughout the entire vegetation season but only a small sample of insects collected at the beginning of the flight period. The species \u003cem\u003eHistiostoma piceae\u003c/em\u003e and \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e are recorded for the first time as forming phoretic relationships with this host. This aspect can be explained by the large number of hosts used by these two species for transportation to other habitats (Hofstetter et al. 2015; Khaustov et al. 2018).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.3. Community diversity and structure\u003c/h2\u003e \u003cp\u003eThe species of phoretic mites and their abundance on the host varied between the native bark beetle species and the invasive species. Diversity indices indicate that the phoretic mite community of \u003cem\u003eIps duplicatus\u003c/em\u003e is more homogeneous and uniform than the bark beetle community of \u003cem\u003eIps typographus\u003c/em\u003e. Although the phoretic mite population of \u003cem\u003eIps typographus\u003c/em\u003e was richer in species, the importance and weight of the dominant species, \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e, was very high. This aspect is especially observable in the values obtained for the Berger-Parker index, which expresses the proportional importance of the most abundant species in a community (Berger and Parker 1970). The results of the PERMANOVA analysis show that the two communities differ significantly from each other. Similar results were obtained by Vissa et al. (2019), who analyzed the phoretic mite communities of three species of pine bark beetles in Portugal. These results further reinforce the proposed hypothesis that the phoretic mite communities of different species of bark beetles differ in terms of abundance and species structure. Although phoretic mite species, in general, exhibit a generalist behavior regarding host selection and are rather specific to certain habitats (Pfammatter et al. 2016), most species identified in this study recorded a higher number on \u003cem\u003eIps typographus\u003c/em\u003e beetles compared to \u003cem\u003eIps duplicatus\u003c/em\u003e beetles. It is possible that some species of phoretic mites, at the local level, may exhibit host specificity when selecting a host for transportation to a new subcortical microhabitat (Lindquist 1970), even though globally they are associated with a wide range of bark beetles. This hypothesis is supported by the findings of Knee et al. (2013), where, out of 29 analyzed species of bark beetles, approximately 70% of the identified phoretic mite species were associated with only one or two bark beeltles. Factors such as the phenology, behavior of the bark beetle, or the microhabitat created by the host in its galleries may play a significant role in host selection (Knee et al. 2013). Additionally, the fact that \u003cem\u003eIps duplicatus\u003c/em\u003e is a relatively new species in the respective area cannot be overlooked, which may have limited its ability to establish strong relationships with all the mite species identified in this study. Another factor that may have influenced the choice of vectors for transporting phoretic mites is the size of the two species of bark beetles, with \u003cem\u003eIps duplicatus\u003c/em\u003e being considerably smaller than \u003cem\u003eIps typographus\u003c/em\u003e (Olenici et al. 2009), thus the surface area for attachment being reduced, particularly disadvantaging species that do not have specialized organs for attachment to the phoront or those that are larger, such as \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e (Moser et al. 1989a).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Localization of phoretic mites on the bodies of bark beetles\u003c/h2\u003e \u003cp\u003eThe attachment of phoretic mites to the bodies of bark beetles generally occurs using the anal pedicel, chelicerae, or special mouthpieces for attachment (Bartlow and Agosta 2021). The distribution of phoretic mites is not random; certain areas of the host's body are chosen based on the phoretic species (Houck and O'Connor 1991), as well as the possibility of being removed from the host's body (Cejka and Holusa 2014). Many studies that have examined this stage of the phoretic relationship have shown that the most prone areas for phoretic mite attachment to the host's body are under the elytra, followed by the thorax and abdomen (Cilbircioğlu et al. 2021; Gwiazdowicz et al. 2015; Manu et al. 2017; Moser and Bogenschu\u0026uuml;tz 1984; Moser et al. 1989a; Paraschiv et al. 2018; Paraschiv and Isaia 2020; Poliță et al. 2016). These results somewhat align with those obtained in this study, where most phoretic mites were identified on the bodies of \u003cem\u003eIps typographus\u003c/em\u003e beetles under the elytra, followed by the thorax, abdomen, elytra, and abdomen, while in the case \u003cem\u003eof Ips duplicatus\u003c/em\u003e beetles, they were found under the elytra, followed by the abdomen, thorax, and legs. The reason that the area under the elytra was the most phoretic in both species is due to the large number of \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e individuals predominantly found in this area of the body (Khaustov et al. 2018). Species such as \u003cem\u003eTrichouropoda polytricha\u003c/em\u003e and \u003cem\u003eUroobovella ipidis\u003c/em\u003e attach to the host's body using the anal pedicel in the thorax or abdomen area (Moser and Bogenschu\u0026uuml;tz 1984). However, this preference can be affected by intra- and interspecific competition, leading mites to choose other parts of the body (Paraschiv and Isaia 2020). This is evidenced in the observations of this study, where \u003cem\u003eUroobovella ipidis\u003c/em\u003e was identified on the thorax, followed by the abdomen in the case of \u003cem\u003eIps duplicatus\u003c/em\u003e beetles, and on the first pair of legs in the case of \u003cem\u003eIps typographus\u003c/em\u003e beetles. \u003cem\u003eHistiostoma piceae\u003c/em\u003e does not have a specific preference for a particular attachment site on the host's body (Khaustov et al. 2018); however, observations made in this study indicate a preference for the thorax of the hosts. An interesting aspect is that this species has been documented as having a hyperphoretic behavior with \u003cem\u003eUroobovella ipidis\u003c/em\u003e mites (Khaustov et al. 2016). In this study, hyperphoretic behavior was observed with individuals of the \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e species, which may explains the results of other studies that identified \u003cem\u003eHistiostoma piceae\u003c/em\u003e predominantly under the elytra (Moser and Bogenschu\u0026uuml;tz 1984; Paraschiv and Isaia 2020).\u003c/p\u003e \u003cp\u003eIn the case of \u003cem\u003eIps typographus\u003c/em\u003e beetles, the \u003cem\u003eElattoma\u003c/em\u003e sp. mites did not show a specific preference, while for \u003cem\u003eIps duplicatus\u003c/em\u003e beetles, they were found between the first and second pairs of legs on the thorax or abdomen. This behavior aligns with the observations made by Khaustov et al. (2018). \u003cem\u003eParaleius leontonychus\u003c/em\u003e uses its claws to attach to the bodies of its hosts (Ahadiyat and Akrami 2015; Penttinen et al. 2013), which may be a reason for its lack of preference in attaching to the host's body. The size of \u003cem\u003ePleuronectocelaeno austriaca\u003c/em\u003e individuals, which makes it difficult to attach to a phoront, could explain why most specimens of this species were found under the elytra, a behavior also reported in other studies of species in this genus (Cilbircioğlu et al. 2021; Pernek et al. 2012). The fact that \u003cem\u003eProctolaelaps fiseri\u003c/em\u003e did not show a preference for attachment is supported by the results of other studies (Khaustov et al. 2018; Paraschiv and Isaia 2020).\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eIn this study, the populations of phoretic mites associated with two species of bark beetles were analyzed, the native species \u003cem\u003eIps typographus\u003c/em\u003e and the invasive species \u003cem\u003eIps duplicatus\u003c/em\u003e. The comparative analysis between the phoretic mite populations of these two bark beetle species highlighted considerable differences in terms of the rate of phoresy, the dynamics of the phoresy rate, as well as the structure and abundance of the two communities. The distribution of mites on the host bodies varied depending on the mite species and the abundance of mites on the hosts. Among the 9 species of phoretic mites identified in this study, 3 are reported for the first time in Romania: \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e, \u003cem\u003eElattoma\u003c/em\u003e sp., and \u003cem\u003eParaleius leontonychus\u003c/em\u003e. Although both the phoresy rate and its dynamics varied between the two hosts throughout the vegetation season, the maximum phoresy for both bark beetle species was reached at the beginning of the flight of the hibernating generation, indicating this as the most important moment for the dissemination of mites into new habitats. The most abundant species on the bodies of \u003cem\u003eIps typographus\u003c/em\u003e beetles was \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e, which accounted for over half of the entire population. In the case of \u003cem\u003eIps duplicatus\u003c/em\u003e bark beetles, the population was dominated by specimens of \u003cem\u003eDendrolaelaps quadrisetus\u003c/em\u003e and \u003cem\u003eElattoma\u003c/em\u003e sp., with the latter being the only species exhibiting this behavior in host selection.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eD.T. Investigation, Methodology, Entomological material analyzed, Formal analysis, Writing - oroginal draft; G.I. Conceptualization, Methodology, Writing\u0026ndash; review \u0026amp; editing; M.M. Entomological material analyzed; Writing\u0026ndash; review \u0026amp; editing; D.S. Conceptualization, Supervision, Writing\u0026ndash; review \u0026amp; editing\u003c/p\u003e\u003ch2\u003eAcknowledgments:\u003c/h2\u003e \u003cp\u003eThis research was funded by PN 23090102, funded by the Ministry of Research, Innovation and Digitalization of Romania and in the frame of the project number RO1567-IBB01/2025, Institute of Biology Bucharest, Romanian Academy. The authors are grateful to all students from the Faculty of Silviculture and Forest Engineering Brașov for their voluntary help in collecting the field data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAhadiyat A, Akrami MA (2015) Oribatid mite (Acari: Oribatida) associated with bark beetles (Coleoptera: Curculionidae: Scolytinae) in Iran, with a review on \u003cem\u003eParaleius leontonychus\u003c/em\u003e (Berlese) and a list of bark beetles in association with this species. 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Recently, \u003cem\u003eIps duplicatus\u003c/em\u003e (Sahlberg, 1836), another species of bark beetle, primarily affecting the genus \u003cem\u003ePicea\u003c/em\u003e, has expanded its range westwards in Europe. In spruce stands, bark beetle populations are closely associated with various organisms such as fungi, nematodes, and mites. Mites, due to the lack of specialized dispersal organs for covering long distances, use bark beetles through a phenomenon known as phoresy. While phoretic mites and their relationship with \u003cem\u003eIps typographus\u003c/em\u003e have been extensively studied in Europe, very few studies have focused on the populations of phoretic mites associated with \u003cem\u003eIps duplicatus\u003c/em\u003e. The aim of this study is to analyze and document the communities of phoretic mites and their complex relationship with the two species of bark beetles in the same location. The research was conducted in a stand located at the lower limit of spruce, where the two pest species have developed outbreaks together. Over 50,000 beetles were collected using wing-type pheromone traps, of which 4,348 were analyzed for the determination of phoretic mites (2,413 \u003cem\u003eIps typographus\u003c/em\u003e; 1,935 \u003cem\u003eIps duplicatus\u003c/em\u003e). In total, nine species of phoretic mites were identified, of which only six were found on \u003cem\u003eIps duplicatus\u003c/em\u003e. Among the nine species, \u003cem\u003eDendrolaelaps disetus\u003c/em\u003e (Hirschmann, 1960), \u003cem\u003eElattoma sp.\u003c/em\u003e, and \u003cem\u003eParaleius leontonychus\u003c/em\u003e (Berlese, 1910) are reported for the first time in Romania. The results highlighted that although \u003cem\u003eIps typographus\u003c/em\u003e beetles were significantly more phorezed than \u003cem\u003eIps duplicatus\u003c/em\u003e beetles throughout the entire flight period, the peaks of phoretic rates were similar. ONE-WAY PERMANOVA test revealed significant differences between the two phoretic mite communities, differences also highlighted by diversity indices. These differences are most likely due to the presence of certain mite species only on \u003cem\u003eIps typographus\u003c/em\u003e beetles, as well as differences between the populations of common species. Regarding the location of phoretic mites on the insects' bodies, this varied depending on the mite species and the host.\u003c/p\u003e","manuscriptTitle":"Phoretic mite communities associated with Ips typographus (Linnaeus, 1758) and Ips duplicatus (Sahlber, 1836) (Coleoptera: Scolytinae) in a Norway spruce stand","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-06 15:35:32","doi":"10.21203/rs.3.rs-6528419/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":"a911a0aa-8c0b-43b0-9fb5-a8b6c7e64555","owner":[],"postedDate":"May 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-01T16:02:25+00:00","versionOfRecord":{"articleIdentity":"rs-6528419","link":"https://doi.org/10.1007/s10493-025-01053-3","journal":{"identity":"experimental-and-applied-acarology","isVorOnly":false,"title":"Experimental and Applied Acarology"},"publishedOn":"2025-08-25 15:57:08","publishedOnDateReadable":"August 25th, 2025"},"versionCreatedAt":"2025-05-06 15:35:32","video":"","vorDoi":"10.1007/s10493-025-01053-3","vorDoiUrl":"https://doi.org/10.1007/s10493-025-01053-3","workflowStages":[]},"version":"v1","identity":"rs-6528419","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6528419","identity":"rs-6528419","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}