Congruence between co-occurrence and trait-based networks is scale-dependent: a case study with flea parasites of small mammalian hosts.

We applied a novel framework based on network theory and a concept of modularity that estimates congruence between trait-based ( = functional) co-occurrence networks, thus allowing the inference of co-occurrence patterns and the determination of the predominant mechanism of community assembly. The aim was to investigate the relationships between species co-occurrence and trait similarity in flea communities at various scales (compound communities: across regions within a biogeographic realm or across sampling sites within a geographic region; component communities: across sampling sites within a geographic region; and infracommunities: within a sampling site). We found that compound communities within biogeographic realms were assembled via environmental or host-associated filtering. In contrast, functional and spatial/host-associated co-occurrence networks, at the scale of regional compound communities, mostly indicated either stochastic processes or the lack of dominance of any deterministic process. Analyses of congruence between functional and either spatial (for component communities) or host-associated (for infracommunities) co-occurrence networks demonstrated that assembly rules in these communities varied among host species. In component communities, stochastic processes prevailed, whereas environmental filtering was indicated in 4 and limiting similarity/competition in 9 of 31 communities. Limiting similarity/competition processes dominated in infracommunities, followed by stochastic mechanisms. We conclude that assembly processes in parasite communities are scale-dependent, with different mechanisms acting at different scales.

Dispersal-based versus niche-based processes as drivers of flea species composition on small mammalian hosts: inferences from species occurrences at large and small scales.

Biological communities may be assembled by both niche-based and dispersal-based (= historic) processes with the relative importance of these processes in community assembly being scale- and context-dependent. To infer whether (a) niche-based or dispersal-based processes play the main role in the assembly of flea communities parasitic on small mammals and whether (b) the main processes of flea community assembly are scale-dependent, we applied a novel permutation-based algorithm (PER-SIMPER) and the dispersal-niche continuum index (DNCI), to data on the species incidence of fleas and their hosts at two spatial scales. At the larger (continental) scale, we analysed flea communities in four biogeographic realms across adjacent continental sections. At the smaller (local) scale, we considered flea communities across two main regions (lowlands and mountains) and seven habitat types within Slovakia. Our analyses demonstrated that species composition of fleas and their small mammalian hosts depended predominantly on historical processes (dispersal) at both scale. This was true for the majority of biogeographic realms at continental scale (except the Nearctic) and both regions at local scale. Nevertheless, strong niche-based assembly mechanism was found in the Nearctic assemblages. At local scale, the intensity of dispersal processes was weaker and niche-driven processes were stronger between habitats within a region than between mountain and lowland regions. We provide historical and ecological explanations for these patterns. We conclude that the assembly of compound flea communities is governed, to a great extent, by the dispersal processes acting on their hosts and, to a lesser extent, by the niche-based processes.

Parasite counts or parasite incidences? Testing differences with four analyses of infracommunity modelling for seven parasite-host associations.

One of the challenges in studies of parasite community ecology is whether the input data for analyses should be parasite abundances/counts, i.e. count data (CD), or parasite incidences (presences/absences), i.e. incidence data (ID). We analysed species responses to environmental factors and species associations in the infracommunities of helminths and ectoparasites in four hosts from Europe (Sorex araneus and Myodes glareolus) and South Africa (Rhabdomys pumilio and Rhabdomys dilectus) and compared the results of four analyses [redundancy analysis (RD), RLQ analysis, joint species distribution modelling (JSDM) and Markov random fields (MRF)] that used either CD or ID as an input. In addition, we compared the differences between the CD and ID results of two analyses (JSDM and MRF) across parasite species between (a) host species within helminths and ectoparasites; (b) helminths and ectoparasites within a host species; and (c) parasite species with contrasting levels of intensity. The results of most analyses for the majority of parasite-host associations were qualitatively similar. However, models based on the ID input performed better than models based on the CD input in three out of four types of analyses (RDA, JSDM and MRF). The differences between the CD and ID models varied between host species (being the lowest in R. pumilio for JSDM and in S. araneus for MRF). However, they were not affected by the level of parasite intensity.

Circulation of Rickettsia species and rickettsial endosymbionts among small mammals and their ectoparasites in Eastern Slovakia.

Bacteria belonging to the genus Rickettsia are known as causative agents of vector-borne zoonotic diseases, such as spotted fevers, epidemic typhus and endemic typhus. Different species of ticks, mites and fleas could act as reservoirs and arthropod vectors of different pathogenic Rickettsia species. The aim of this work was to establish active surveillance of Rickettsia spp. in mites, ticks and fleas collected from small mammals (rodents and shrews) in Eastern Slovakia. A total of 964 animal ear biopsies, 871 mites, 667 ticks and 743 fleas were collected from small mammals in the Kosice region, Eastern Slovakia. All specimens were identified using specialized taxonomic keys, and were conserved in ethanol until DNA extraction was performed. After DNA extraction, identification of Rickettsia species was performed by PCR-based methods. The total prevalence of rickettsiae from ear biopsies was 4.6% (95% CI, 3.2-5.9), in tested mites 9.3% (95% CI, 7.4-11.2), 17.2% (95% CI, 14.3-20.1) in I. ricinus ticks and 3.5% (95% CI, 2.2-4.8) in fleas. Sequence analysis of the partial gltA gene and Rickettsia helvetica-, Rickettsia slovaca-, Rickettsia raoultii- species specific real-time PCR tests revealed the presence of R. helvetica, R. slovaca, unidentified Rickettsia and rickettsial endosymbionts. These pathogenic and symbiotic species were confirmed in the following ectoparasite species-Laelaps jettmari, Haemogamasus nidi, Laelaps agilis and Eulaelaps stabularis mites, Ixodes ricinus ticks, Ctenophthalmus solutus, C. assimilis and Megabothris turbidus fleas infesting host-Apodemus agrarius, A. flavicollis, Microtus arvalis and Myodes glareolus small mammals. These results confirm the circulation of R. helvetica, R. slovaca, unidentified Rickettsia and rickettsial endosymbionts in mites, ticks and fleas collected on small mammals in the Kosice region, Eastern Slovakia.

Associations between different Laelapidae (Mesostigmata: Dermanyssoidea) mites and small rodents from Lithuania.

Associations between species of Laelapidae (Mesostigmata: Dermanyssoidea) mites and small rodents have been studied insufficiently. The aim of this study was to investigate infestation patterns of small rodent species by laelapid mites at six locations in Lithuania. A total of 728 rodents were snap- and live-trapped in various locations during 2013-2016. Eight rodent species were identified, namely Apodemus flavicollis, Apodemus agrarius, Myodes glareolus, Micromys minutus, Mus musculus, Microtus oeconomus, Microtus arvalis and Microtus agrestis. A total of 343 (47.1%) rodents were found to be infested with up to eight species of parasitic mites from the Laelapidae family (n = 1363): Laelaps agilis, Laelaps hilaris, Hyperlaelaps microti, Haemogamasus nidi, Haemogamasus hirsutus, Eulaelaps stabularis, Hirstionyssus sunci and Myonyssus gigas. The dominant species of mite found on rodents was L. agilis (89.1%), found on 43.4% of all hosts. Abundance and mean intensity of infestation with mites varied among species of hosts and were highest for A. flavicollis. We document new geographical and host records for gamasid mites of eight rodent species in Lithuania.

Mysteries of host switching: Diversification and host specificity in rodent-coccidia associations.

Recent studies show that host switching is much more frequent than originally believed and constitutes an important driver in evolution of host-parasite associations. However, its frequency and ecological mechanisms at the population level have been rarely investigated. We address this issue by analyzing phylogeny and population genetics of an extensive sample, from a broad geographic area, for commonly occurring parasites of the genus Eimeria within the abundant rodent genera Apodemus, Microtus and Myodes, using two molecular markers. At the most basal level, we demonstrate polyphyletic arrangement, i.e. multiple origin, of the rodent-specific clusters within the Eimeria phylogeny, and strong genetic/phylogenetic structure within these lineages determined at least partially by specificities to different host groups. However, a novel and the most important observation is a repeated occurrence of host switches among closely related genetic lineages which may become rapidly fixed. Within the studied model, this phenomenon applies particularly to the switches between the eimerians from Apodemus flavicollis/Apodemus sylvaticus and Apodemus agrarius groups. We show that genetic differentiation and isolation between A. flavicollis/A. sylvaticus and A. agrarius faunas is a secondary recent event and does not reflect host-parasite coevolutionary history. Rather, it provides an example of rapid ecology-based differentiation in the parasite population.

Cryptosporidium infecting wild cricetid rodents from the subfamilies Arvicolinae and Neotominae.

We undertook a study on Cryptosporidium spp. in wild cricetid rodents. Fecal samples were collected from meadow voles (Microtus pennsylvanicus), southern red-backed voles (Myodes gapperi), woodland voles (Microtus pinetorum), muskrats (Ondatra zibethicus) and Peromyscus spp. mice in North America, and from bank voles (Myodes glareolus) and common voles (Microtus arvalis) in Europe. Isolates were characterized by sequence and phylogenetic analyses of the small subunit ribosomal RNA (SSU) and actin genes. Overall, 33·2% (362/1089) of cricetids tested positive for Cryptosporidium, with a greater prevalence in cricetids from North America (50·7%; 302/596) than Europe (12·1%; 60/493). Principal Coordinate analysis separated SSU sequences into three major groups (G1-G3), each represented by sequences from North American and European cricetids. A maximum likelihood tree of SSU sequences had low bootstrap support and showed G1 to be more heterogeneous than G2 or G3. Actin and concatenated actin-SSU trees, which were better resolved and had higher bootstrap support than the SSU phylogeny, showed that closely related cricetid hosts in Europe and North America are infected with closely related Cryptosporidium genotypes. Cricetids were not major reservoirs of human pathogenic Cryptosporidium spp.

Phylogenetic analysis of Puumala virus strains from Central Europe highlights the need for a full-genome perspective on hantavirus evolution.

Puumala virus (PUUV), carried by bank voles (Myodes glareolus), is the medically most important hantavirus in Central and Western Europe. In this study, a total of 523 bank voles (408 from Germany, 72 from Slovakia, and 43 from Czech Republic) collected between the years 2007-2012 were analyzed for the presence of hantavirus RNA. Partial PUUV genome segment sequences were obtained from 51 voles. Phylogenetic analyses of all three genome segments showed that the newfound strains cluster with other Central and Western European PUUV strains. The new sequences from Sumava (Bohemian Forest), Czech Republic, are most closely related to the strains from the neighboring Bavarian Forest, a known hantavirus disease outbreak region. Interestingly, the Slovak strains clustered with the sequences from Bohemian and Bavarian Forests only in the M but not S segment analyses. This well-supported topological incongruence suggests a segment reassortment event or, as we analyzed only partial sequences, homologous recombination. Our data highlight the necessity of sequencing all three hantavirus genome segments and of a broader bank vole screening not only in recognized endemic foci but also in regions with no reported human hantavirus disease cases.

Beta-diversity of ectoparasites at two spatial scales: nested hierarchy, geography and habitat type.

Beta-diversity of biological communities can be decomposed into (a) dissimilarity of communities among units of finer scale within units of broader scale and (b) dissimilarity of communities among units of broader scale. We investigated compositional, phylogenetic/taxonomic and functional beta-diversity of compound communities of fleas and gamasid mites parasitic on small Palearctic mammals in a nested hierarchy at two spatial scales: (a) continental scale (across the Palearctic) and (b) regional scale (across sites within Slovakia). At each scale, we analyzed beta-diversity among smaller units within larger units and among larger units with partitioning based on either geography or ecology. We asked (a) whether compositional, phylogenetic/taxonomic and functional dissimilarities of flea and mite assemblages are scale dependent; (b) how geographical (partitioning of sites according to geographic position) or ecological (partitioning of sites according to habitat type) characteristics affect phylogenetic/taxonomic and functional components of dissimilarity of ectoparasite assemblages and (c) whether assemblages of fleas and gamasid mites differ in their degree of dissimilarity, all else being equal. We found that compositional, phylogenetic/taxonomic, or functional beta-diversity was greater on a continental rather than a regional scale. Compositional and phylogenetic/taxonomic components of beta-diversity were greater among larger units than among smaller units within larger units, whereas functional beta-diversity did not exhibit any consistent trend regarding site partitioning. Geographic partitioning resulted in higher values of beta-diversity of ectoparasites than ecological partitioning. Compositional and phylogenetic components of beta-diversity were higher in fleas than mites but the opposite was true for functional beta-diversity in some, but not all, traits.

Genetic diversity of Bartonella genotypes found in the striped field mouse (Apodemus agrarius) in Central Europe.

We investigated the diversity of Bartonella in Apodemus agrarius, an important rodent of peri-domestic habitats, which has spread into Europe in the past 1000 years. Spleen samples of 344 A. agrarius from Eastern Slovakia were screened for the presence of Bartonella spp. using 16S-23S rRNA internal transcribed spacer region and bacteria were detected in 9% of rodents. Based on sequencing of three housekeeping genes (gltA, rpoB and groEL) Bartonella genotypes were ascribed to the species typical for mice and voles: B. grahamii, B. taylorii and B. birtlesii. However, the study also confirmed presence of genotypes belonging to the B. clarridgeiae/B. rochalimae clade, and the B. elizabethae/B. tribocorum clade, which are not commonly found in woodland rodents. In addition, a potential recombination event between these two genotypes was noted, which highlights an important role of A. agrarius in shaping Bartonella diversity and evolution.

Seasonal analysis of Rickettsia species in ticks in an agricultural site of Slovakia.

Many rickettsiae of the spotted fever group are emerging pathogens causing serious diseases associated with vertebrate hosts. Ixodidae ticks are known as their vectors. Investigation of the relative abundance of questing Ixodes ricinus and their infection with Rickettsia spp. in an agricultural site comprising a game reserve in Slovakia was the aim of this study. In total, 2198 I. ricinus (492 larvae, 1503 nymphs and 203 adults) were collected by flagging the vegetation along 100 m(2) transects in Rozhanovce (eastern Slovakia): 334, 595 and 1269 in 2011, 2012 and 2013, respectively. Considering questing nymphs and adults, the highest relative density of 81 individuals/100 m(2) was observed in May 2013, the lowest of 0.3 individuals/100 m(2) in March 2012. A total of 1056 ticks (853 nymphs, 100 females and 103 males; 2011: n = 329, 2012: n = 509 and 2013: n = 218) were individually screened by PCR-based methods for the presence of Rickettsia spp. The overall prevalences were 7.3% for nymphs, 15% for females, 7.8% for males; 7.0% in 2011, 8.4% in 2012, and 8.7% in 2013. The maximum prevalences were observed in July in nymphs and in May in adults. Sequencing showed infection with R. helvetica in 73 ticks (72.6% nymphs, 16.4% females, 11% males) and with R. monacensis in 11 ticks (8 nymphs, 3 females). The results showed the circulation of pathogenic Rickettsia species in the agricultural site and a potential risk for humans to encounter infected ticks.

Environment-related and host-related factors affecting the occurrence of lice on rodents in Central Europe.

We studied the effects of environment- (habitat, season) and host-related (sex, body mass) factors on the occurrence of four species of lice (Insecta:Phthiraptera:Anoplura) on six rodent species (Rodentia:Muridae). We asked how these factors influence the occurrence of lice on an individual host and whether different rodent-louse associations demonstrate consistent trends in these effects. We found significant effects of at least one environment-related and at least one host-related factor on the louse occurrence in five of six host-louse associations. The effect of habitat was significant in two associations with the occurrence of lice being more frequent in lowland than in mountain habitats. The effect of season was significant in five associations with a higher occurrence of infestation during the warm season in four associations and the cold season in one association. Host sex affected significantly the infestation by lice in three associations with a higher frequency of infestation in males. Host body mass affected the occurrence of lice in all five associations, being negative in wood mice and positive in voles. In conclusion, lice were influenced not only by the host- but also by environment-related factors. The effects of the latter could be mediated via life history parameters of a host.

Rickettsia species in fleas collected from small mammals in Slovakia.

Epidemiological and epizootiological studies of Rickettsia felis and other Rickettsia spp. are very important, because their natural cycle has not yet been established completely. In total, 315 fleas (Siphonaptera) of 11 species of Ceratophyllidae, Hystrichopsyllidae and Leptopsyllidae families were tested for the presence of Rickettsia species and Coxiella burnetii with conventional and specific quantitative real-time PCR assays. Fleas were collected from five rodent hosts (Myodes glareolus, Apodemus flavicollis, Apodemus agrarius, Microtus subterraneus, Microtus arvalis) and three shrew species (Sorex araneus, Neomys fodiens, Crocidura suaveolens) captured in Eastern and Southern Slovakia. Overall, Rickettsia spp. was found in 10.8% (34/315) of the tested fleas of Ctenophthalmus agyrtes, Ctenophthalmus solutus, Ctenophthalmus uncinatus and Nosopsyllus fasciatus species. Infected fleas were coming from A. flavicollis, A. agrarius, and M. glareolus captured in Eastern Slovakia. C. burnetii was not found in any fleas. R. felis, Rickettsia helvetica, unidentified Rickettsia, and rickettsial endosymbionts were identified in fleas infesting small mammals in the Kosice region, Eastern Slovakia. This study is the first report of R. felis infection in C. solutus male flea collected from A. agrarius in Slovakia.

Subtyping Cryptosporidium ubiquitum,a zoonotic pathogen emerging in humans.

Cryptosporidium ubiquitum is an emerging zoonotic pathogen. In the past, it was not possible to identify an association between cases of human and animal infection. We conducted a genomic survey of the species, developed a subtyping tool targeting the 60-kDa glycoprotein (gp60) gene, and identified 6 subtype families (XIIa-XIIf) of C. ubiquitum. Host adaptation was apparent at the gp60 locus; subtype XIIa was found in ruminants worldwide, subtype families XIIb-XIId were found in rodents in the United States, and XIIe and XIIf were found in rodents in the Slovak Republic. Humans in the United States were infected with isolates of subtypes XIIb-XIId, whereas those in other areas were infected primarily with subtype XIIa isolates. In addition, subtype families XIIb and XIId were detected in drinking source water in the United States. Contact with C. ubiquitum-infected sheep and drinking water contaminated by infected wildlife could be sources of human infections.

Variable effects of host characteristics on species richness of flea infracommunities in rodents from three continents.

We studied the effect of host gender and body mass on species richness of flea infracommunities in nine rodent host species from three biomes (temperate zone of central Europe, desert of the Middle East and the tropics of East Africa). Using season- and species-specific generalized linear mixed models and controlling for year-to-year variation, spatial clustering of rodent sampling and over-dispersion of the data, we found inconsistent associations between host characteristics and flea species richness. We found strong support for male-biased flea parasitism, especially during the reproductive period (higher species richness in male hosts than in females) in all considered European rodents (Apodemus agrarius, Myodes glareolus and Microtus arvalis) and in one rodent species from the Middle East (Dipodillus dasyurus). In contrast, two of three African rodent species (Lophuromys kilonzoi and Praomys delectorum) demonstrated a trend of female-biased flea species richness. Positive associations between body mass and the number of flea species were detected mainly in males (five of nine species: A. agrarius, M. glareolus, M. arvalis, D. dasyurus and Mastomys natalensis) and not in females (except for M. natalensis). The results of this study support earlier reports that gender-biased, in general, and male-biased, in particular, infestation by ectoparasites is not a universal rule. This suggests that mechanisms of parasite acquisition by an individual host are species-specific and have evolved independently in different rodent host-flea systems.

Micromammals as a reservoir for the zoonotic nematode Calodium hepaticum (syn. Capillaria hepatica) in recreational areas of Slovakia.

The hepatic nematode Calodium hepaticum is a zoonotic parasite primarily parasitising small mammals, but it can infect a wide range of mammal species, including humans. Due to its specific life cycle and transmission pattern, it is one of the least studied helminths in the world. The only documented findings of C. hepaticum from Slovakia (former Czechoslovakia) come from the 60s and 70s of the 20th Century, including nine human cases of the infection reported post-mortem. The present study was conducted in the area of these original records in the Tatra National Park (TANAP) and the Kosice Zoo. In TANAP, 484 small mammals of six shrew species (Insectivora: Soricidae) and eight rodent species (Rodentia: Muroidea) were collected. In the Kosice Zoo, 163 rodents from 10 species were sampled. All specimens were examined for the presence of C. hepaticum eggs using the artificial digestion method. The parasite was recorded in two shrew species (Sorex araneus and Neomys fodiens) and five rodent species (Arvicola amphibius, Microtus agrestis, Clethrionomys glareolus, Apodemus flavicollis, and Rattus norvegicus) from TANAP, while in the Kosice Zoo only a single individual of R. norvegicus was found to be infected.

The Impact of Altitude on Tick-Borne Pathogens at Two Mountain Ranges in Central Slovakia.

Ticks are ectoparasites of a wide range of animals and are important vectors of numerous pathogens affecting humans, livestock, and pets. This study investigates possible correlations between selected factors, altitude, soil pH, and a factor called 'amount' (number of ticks examined in pooled samples) on the occurrence of I. ricinus ticks positive for selected tick-borne microorganisms. Questing I. ricinus ticks were collected in 2016 and 2017 across various altitudes, at two mountain ranges in central Slovakia. Tick pools were screened for the presence of Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato (Bbsl), Babesia/Theileria spp., Rickettsia spp., and tick-borne encephalitis virus (TBEV) using molecular methods. Regression analysis was employed to evaluate relationships between selected factors and the occurrence of vector-borne microorganisms. This study revealed a statistically significant influence of altitude on the occurrence of A. phagocytophilum; increasing altitude of the sampling site was associated with increased probability of pathogen occurrence. For Babesia/Theileria spp., neither altitude nor soil pH significantly affected pathogen occurrence. The occurrence of Bbsl was notably impacted by both altitude and soil pH; higher altitudes were associated with a decreased probability of pathogen presence, whereas higher soil pH increased the likelihood of pathogen occurrence. The presence of Rickettsia in a pooled sample was not affected by altitude and soil pH, but the 'amount' factor was a significant predictor, increasing the probability of pathogen detection. Neither altitude nor soil pH had a significant impact on TBEV occurrence. The regression models showed moderate goodness-of-fit levels to the data, underscoring their utility in examining the role of altitude and soil pH on pathogen occurrence. However, they explained only a small portion of the overall variance in pathogen occurrence, indicating the presence of other significant factors not covered in this study.

Ixodiphagus hookeri (Hymenoptera: Encyrtidae) and Tick-Borne Pathogens in Ticks with Sympatric Occurrence (and Different Activities) in the Slovak Karst National Park (Slovakia), Central Europe.

Ticks are involved in the transmission a plethora of pathogens. To effectively control ticks and mitigate the risks associated with tick-borne diseases, it is important to implement tick control measures. These may include the use of acaricides as well as the development and implementation of an alternative, environmentally friendly tick management program that include practices such as habitat modification or establishing biological control. Ixodiphagus hookeri Howard is a tick-specific parasitoid wasp that predates on several species of ixodid ticks and could contribute to the control of the tick population. This work aimed to detect the presence of parasitoid wasps in ticks (Ixodidae) using genetic approaches. Several tick species of the genera Ixodes, Haemaphysalis, and Dermacentor, with a sympatric occurrence in the Slovak Karst National Park in southeastern Slovakia, were screened for the presence of wasps of the genus Ixodiphagus. The DNA of the parasitoids was detected in four tick species from three genera. This work presents the first molecular detection of parasitoids in two Dermacentor tick species, as well as the first molecular identification of Ixodiphagus wasps in Ixodes ricinus and Haemaphysalis concinna ticks from the Karst area. In the given area, it was observed that I. ricinus and H. concinna ticks are hyper-parasitized by wasps. Moreover, it was observed that wasps here can parasitize several tick species, some of which are of less significance for human and animal health (as they transmit fewer pathogens).

Structure of compound and component communities of fleas parasitic on small mammals in six different regions as revealed by environmental-based co-occurrence geometry analyses.

We inferred the patterns of co-occurrence of flea species in compound (across all host species) and component (across conspecific hosts) communities from six regions of the world (Mongolia, Northwest Argentina, Argentinian Patagonia, West Siberia, Slovakia, and South Africa) using the novel eigenvector ellipsoid method. This method allows us to infer structural community patterns by comparing species' environmental requirements with the pattern of their co-occurrences. We asked whether: (a) communities are characterized by species segregation, nestedness, or modularity; (b) patterns detected by the novel method conform to the patterns identified by traditional methods that search for non-randomness in community structure; and (c) the pattern of flea species co-occurrences in component communities is associated with host species traits. The results of the application of the eigenvector ellipsoid method suggested that the co-occurrence of flea species was random in all compound communities except in South Africa, where this community demonstrated a tendency to be nested. Flea species co-occurrences were random in many component communities. Species segregation was detected in the flea community of one host, whereas the flea communities of 14 hosts from different regions appeared to be nested. No indication of a modular structure in any community was found. The nestedness of flea component communities was mainly characteristic of hosts with a low relative brain mass. We concluded that the application of this novel method that combines data on species distribution and their environmental requirements allows better identification of the community structural patterns and produces more reliable results as compared with traditional methods.

Sex-biased parasitism is not universal: evidence from rodent-flea associations from three biomes.

The distribution of parasites among individual hosts is characterised by high variability that is believed to be a result of variations in host traits. To find general patterns of host traits affecting parasite abundance, we studied flea infestation of nine rodent species from three different biomes (temperate zone of central Europe, desert of Middle East and tropics of East Africa). We tested for independent and interactive effects of host sex and body mass on the number of fleas harboured by an individual host while accounting for spatial clustering of host and parasite sampling and temporal variation. We found no consistent patterns of the effect of host sex and body mass on flea abundance either among species within a biome or among biomes. We found evidence for sex-biased flea infestation in just five host species (Apodemus agrarius, Myodes glareolus, Microtus arvalis, Gerbillus andersoni, Mastomys natalensis). In six rodent species, we found an effect of body mass on flea abundance (all species mentioned above and Meriones crassus). This effect was positive in five species and negative in one species (Microtus arvalis). In M. glareolus, G. andersoni, M. natalensis, and M. arvalis, the relationship between body mass and flea abundance was mediated by host sex. This was manifested in steeper change in flea abundance with increasing body mass in male than female individuals (M. glareolus, G. andersoni, M. natalensis), whereas the opposite pattern was found in M. arvalis. Our findings suggest that sex and body mass are common determinants of parasite infestation in mammalian hosts, but neither of them follows universal rules. This implies that the effect of host individual characteristics on mechanisms responsible for flea acquisition may be manifested differently in different host species.