We investigated phylogenetic patterns in flea assemblages from 80 regions in 6 biogeographic realms and asked whether (a) flea phylogenetic turnover is driven by host phylogenetic turnover, environmental dissimilarity or geographic distance; (b) the relative importance of these drivers differs between realms; and (c) the environmental drivers of flea phylogenetic turnover are similar to those of host phylogenetic turnover. We also asked whether the phylogenetic originality of a flea species correlates with the degree of its host specificity and whether the phylogenetic originality of a host species correlates with the diversity of its flea assemblages. We found that host phylogenetic turnover was the best predictor of flea phylogenetic turnover in all realms, whereas the effect of the environment was weaker. Environmental predictors of flea phylogenetic turnover differed between realms. The importance of spatial distances as a predictor of the phylogenetic dissimilarity between regional assemblages varied between realms. The responses of host turnover differed from those of fleas. In 4 of the 6 realms, geographic distances were substantially better predictors of host phylogenetic turnover than environmental gradients. We also found no general relationship between flea phylogenetic originality and its host specificity in terms of either host species richness or host phylogenetic diversity. We conclude that flea phylogenetic turnover is determined mainly by the phylogenetic turnover of their hosts rather than by environmental gradients. Phylogenetic patterns in fleas are manifested at the level of regional assemblages rather than at the level of individual species.

We used data on the species composition of regional assemblages of fleas and their small mammalian hosts from 6 biogeographic realms and applied a novel method of step-down factor analyses (SDFA) and cluster analyses to identify biogeographic (across the entire globe) and ecological (within a realm across the main terrestrial biomes) clusters of these assemblages. We found that, at the global scale, the clusters of regional assemblage loadings on SDFA axes reflected well the assemblage distribution, according to the biogeographic realms to which they belong. At the global scale, the cluster topology, corresponding to the biogeographic realms, was similar between flea and host assemblages, but the topology of subtrees within realm-specific clusters substantially differed between fleas and hosts. At the scale of biogeographic realms, the distribution of regional flea and host assemblages did not correspond to the predominant biome types. Assemblages with similar loadings on SDFA axes were often situated in different biomes and vice versa. The across-biome, within-realm distributions of flea vs host assemblages suggested weak congruence between these distributions. Our results indicate that dispersal is a predominant mechanism of flea and host community assembly across large regions.

South Africa has a diverse fauna of ixodid tick species, several of which are of medical or veterinary importance. Elucidation of which host or environmental characteristics determine the composition and abundance of tick assemblages is, therefore, highly relevant to disease management and wildlife conservation efforts. Here, we analysed the similarity in ixodid tick assemblages of three wildlife and three livestock species in a natural (Great Fish River Reserve) and anthropogenic (an adjacent farm) habitat in South Africa. We compared tick infracommunities of three wild host species between the reserve and the farm; of three wild host species within the reserve and of wild and livestock species on the farm (considering body size). Hosts examined in this study harboured the adults and immature stages of 11 tick species belonging to five ixodid genera. Notably, several tick species of South African wildlife have successfully made the switch to livestock and thus both wild hosts and livestock now contribute to the pool of maintenance hosts for these ticks as well as their associated pathogens. This is an important consideration when translocating wildlife or livestock as part of farming or conservation activities.

We investigated the patterns of phylogenetic and functional (dis)similarity in the species composition of host spectra between co-habitating generalist flea species in regional assemblages from four continents (Europe, Asia, North America and Africa) using a recently developed ordination approach (Double Similarity Principal Component Analysis). From the functional perspective, we considered physiological [body mass and basal metabolic rate (BMR)] and ecological (shelter depth and complexity) host traits. We asked (a) whether host phylogeny, physiology or ecology is the main driver of (dis)similarities between flea host spectra and (b) whether the patterns of phylogenetic and functional (dis)similarity in host spectra vary between flea assemblages from different continents. Phylogenetic similarity between the host spectra was highest in Africa, lowest in North America and moderate in Europe and Asia. In each assemblage, phylogenetic clusters of hosts dominating in the host spectra could be distinguished. The functional similarity between the host spectra of co-occurring fleas was low for shelter structure in all assemblages and much higher for body mass and BMR in three of the four assemblages (except North America). We conclude that host phylogeny and shelter structure are the main drivers of (dis)similarity between the host spectra of co-habitating fleas. However, the effects of these factors on the patterns of (dis)similarity varied across continents.

We studied patterns of compositional, functional, and phylogenetic α- and β-diversity in flea and gamasid mite infracommunities of small Siberian mammals, taking into account host-associated (species) and environmental (biome or sampling period) factors. We asked: (a) How do these factors and their interactions affect infracommunity diversity? (b) Does infracommunity composition, in terms of species, traits, and phylogenetic lineages, deviate from random? (c) Are species, traits, and phylogenetic lineages in infracommunities clustered or overdispersed?, and (d) Do patterns of diversity differ between the three diversity facets and/or the two ectoparasite taxa? We found that the α-diversity of infracommunities was strongly affected by host species, biome, and sampling period. The highest proportion of infracommunity diversity in both taxa was associated with the interaction between either host species and biome or host species and sampling period. Infracommunities of both taxa within, as well as between, host species, biomes, and sampling periods were characterized by the clustering of species, traits and lineages. The patterns of the effects of host species, biome, and sampling period on infracommunity diversity were congruent among the three diversity facets in both fleas and mites. We conclude that the assembly patterns in ectoparasite infracommunities mirror those characteristics of component and compound communities.

We studied the compositional turnover in infracommunities and component communities of ecto- and endoparasites infesting a bat, Miniopterus natalensis (Chiroptera, Miniopteridae), across seven sampling sites using the zeta diversity metric (measuring similarity between multiple communities) and calculating zeta decline and retention rate (both scales) and zeta decay (component communities). We asked whether the patterns of zeta diversity differ between (a) infracommunities and component communities; (b) ecto- and endoparasites and (c) subsets of communities infecting male and female bats. The pattern of compositional turnover differed between infracommunities and component communities in endoparasites only. The shape of zeta decline for infracommunities indicated that there were approximately equal probabilities of ecto- and endoparasitic species to occur on/in any bat individual within a site. The shape of zeta decline for component communities suggested the stochasticity of ectoparasite turnover, whereas the turnover of endoparasites was driven by niche-based processes. Compositional turnover in component communities of ectoparasites was more spatially dependent than that of endoparasites. Spatial independence of compositional turnover in endoparasites was due to subcommunities harboured by female bats. We conclude that the patterns of compositional turnover in infracommunities were similar in ecto- and endoparasites, whereas the patterns of turnover in component communities differed between these groups.

To model the colonization of a novel host by fleas, Synosternus cleopatrae and Xenopsylla ramesis, we established experimental lines maintained for 15 generations on a principal or a novel host (either co-occurring with a flea or not). We compared the blood meal size and the energy expended for digestion by fleas from the 15th generation of each line on these hosts between hosts within a line and between lines within a host asking (a) whether fleas adapt to a novel host (increased blood consumption/decreased energy expended for digestion); (b) if yes, whether this adaptation leads to the loss of ability to exploit an original host, and (c) whether the success of adaptation to a novel host depends on its ecological co-occurrence with a flea. The blood consumption and digestion energetics of fleas fed on the principal host differed from those on other hosts. The effect of the principal host on feeding performance differed between fleas, with S. cleopatrae consuming less blood and expending more energy for digestion on the principal than on any other host, whereas the opposite was true for X. ramesis. No changes in feeding performance on a novel host over generations were found. We propose several explanations for the lack of adaptation to a novel host over time. We explain the poor performance of S. cleopatrae on its principal host via its immune response mounting pattern. We argue that the principal host of a parasite is not necessarily the host on which the parasite demonstrates the best performance.

Both parasitism and social contact are common sources of stress that many gregarious species encounter in nature. Upon encountering such stressors, individuals secrete glucocorticoids and although short-term elevation of glucocorticoids is adaptive, long-term increases are correlated with higher mortality and deleterious reproductive effects. Here, we used an experimental host-parasite system, social rodents Acomys cahirinus and their characteristic fleas Parapulex chephrenis, in a fully-crossed design to test the effects of social contact and parasitism on stress during pregnancy. By analysing faecal glucocorticoid metabolites, we found that social hierarchy did not have a significant effect on glucocorticoid concentration. Rather, solitary females had significantly higher glucocorticoid levels than females housed in pairs. We found a significant interaction between the stressors of parasitism and social contact with solitary, uninfested females having the highest faecal glucocorticoid metabolite levels suggesting that both social contact and infestation mitigate allostatic load in pregnant rodents. Therefore, the increased risk of infestation that accompanies group-living could be outweighed by positive aspects of social contact within A. cahirinus colonies in nature.

Thirty warthogs, Phacochoerus africanus, were collected in the Pongola Game Reserve, South Africa and examined for helminths. Gastrointestinal helminth assemblages comprised Gastrodiscus aegyptiacus, the cestode genus Moniezia and seven species of nematodes. A single warthog harboured a metacestode of Taenia hydatigena in the mesenteries. No helminths were found in the heart, lungs or liver of the warthogs. Probstmayria vivipara and Murshidia spp. were the most prevalent as well as abundant helminth species, followed by Physocephalus sexalatus. The incidence of Moniezia did not differ between hosts of different sex or age. Numbers of Murshidia spp. were not affected by host sex, but were higher in adults than in juveniles. Conversely, burdens of Trichostrongylus thomasi were not affected by host age, but were higher in males than in females. While not highly significant, helminth assemblages in male warthogs were more species rich than in females. Helminth communities in the three genera of wild sub-Saharan suids are largely unique, but Ph. africanus and Hylochoerus meinertzhageni share more worm species with each other than with Potamochoerus larvatus, possibly because the former two are more closely related. Overlap between helminth communities of African wild suids and those of other suids and Tayassuidae worldwide is limited.

The β-diversity of fleas parasitic on small mammals in 45 regions of the Palearctic was partitioned into species [species contributions to β-diversity (SCBD)] and site ( = assemblage) contributions [local contributions to β-diversity (LCBD)]. We asked what are the factors affecting SCBD and LCBD and tested whether (a) variation in ecological, morphological, life history and geographic traits of fleas can predict SCBD and (b) variation in flea and host community metrics, off-host environmental factors, host species composition of flea assemblages can predict LCBD. We used spatial variables to describe geographic distribution of flea assemblages with various LCBD values. SCBD significantly increased with an increase in abundance and a decrease in phylogenetic host specificity of a flea as well as with size and latitude of its geographic range, but was not associated with any morphological/life history trait. LCBD of flea assemblages did not depend on either flea or host species richness or environmental predictors, but was significantly affected by compositional uniqueness ( = LCBD) of regional host assemblages and variables describing their species composition. In addition, variation in LCBD was also explained by broad-to-moderate-scale spatial variables. We conclude that SCBD of fleas could be predicted via their ecological and geographic traits, whereas LCBD of their assemblages could be predicted via host composition.

To understand existence, patterns and mechanisms behind phylogenetic heritability in the geographic range size (GRS) of parasites, we measured phylogenetic signal (PS) in the sizes of both regional (within a region) and continental (within a continent) geographic ranges of fleas in five regions. We asked whether (a) GRS is phylogenetically heritable and (b) the manifestation of PS varies between regions. We also asked whether geographic variation in PS reflects the effects of the environment's spatiotemporal stability (e.g. glaciation disrupting geographic ranges) or is associated with time since divergence (accumulation differences among species over time). Support for the former hypothesis would be indicated by stronger PS in southern than in northern regions, whereas support for the latter hypothesis would be shown by stronger PS in regions with a large proportion of species belonging to the derived lineages than in regions with a large proportion of species belonging to the basal lineages. We detected significant PS in both regional and continental GRSs of fleas from Canada and in continental GRS of fleas from Mongolia. No PS was found in the GRS of fleas from Australia and Southern Africa. Venezuelan fleas demonstrated significant PS in regional GRS only. Local Indicators of Phylogenetic Association detected significant local positive autocorrelations of GRS in some clades even in regions in which PS has not been detected across the entire phylogeny. This was mainly characteristic of younger taxa.

We revisited the role of dissimilarity of host assemblages in shaping dissimilarity of flea assemblages using a non-linear approach. Generalized dissimilarity models (GDMs) were applied using data from regional surveys of fleas parasitic on small mammals in four biogeographical realms. We compared (1) model fit, (2) the relative effects of host compositional and phylogenetic turnover and geographic distance on flea compositional and phylogenetic turnover, and (3) the rate of flea turnover along gradients of host turnover and geographic distance with those from earlier application of a linear approach. GDMs outperformed linear models in explaining variation in flea species turnover and host dissimilarity was the best predictor of flea dissimilarity, irrespective of scale. The shape of the relationships between flea compositional turnovers along host compositional turnover was similar in all realms, whereas turnover along geographic distance differed among realms. In contrast, the rate of flea phylogenetic turnover along gradients of host phylogenetic turnover differed among realms, whereas flea phylogenetic turnover did not depend on geographic distance in any realm. We demonstrated that a non-linear approach (a) explained spatial variation in parasite community composition better than and (b) revealed patterns that were obscured by earlier linear analyses.

To reveal factors responsible for spatial variation in parasite community composition we studied patterns of similarity in helminth species composition in two closely-related rodents (Rhabdomys pumilio and Rhabdomys dilectus) that differ in their social and spatial behaviour and live under different environmental conditions across 20 localities in South Africa. We asked whether the two hosts harbour similar assemblages, whether these are more dissimilar between than within hosts and if host social structure, behaviour or environment affects similarity patterns in helminth infracommunities within and among localities. We also investigated whether similarity in species composition of helminth component communities decreases with an increase of geographic distance between host populations. We found that the pattern of space use by the hosts rather than their social behaviour promotes differences in helminth species composition between host species as well as among host populations from different localities. The rate of distance decay of similarity in species composition of helminth component communities differed between the two hosts due to difference in the degree of environmental variation across their geographic ranges. We conclude that patterns of spatial variation in helminth species composition are driven mainly by host spatial behaviour and, to a lesser extent, by environment-associated factors.

Environmental fluctuations are expected to require special adaptations only if they are associated with a decrease in fitness. We compared reproductive performance between fleas fed on alternating (preferred and non-preferred) hosts and fleas fed solely on either a preferred or a non-preferred host to determine whether (1) host alternation incurs an immediate negative effect, and, if yes, then (2) whether this effect is greater in a host specialist (Parapulex chephrenis) than in host generalists (Xenopsylla conformis and Synosternus cleopatrae). We also compared flea performance under alternating host regimes with different host order (initial feeding on either a preferred or a non-preferred host). An immediate negative effect of alternating hosts on reproductive performance was found in P. chephrenis only. These fleas produced 44·3% less eggs that were 3·6% smaller when they fed on alternating hosts as compared with a preferred host. In contrast, X. conformis and S. cleopatrae appeared to be able to adapt their reproductive strategy to host alternation by producing higher quality offspring (on average, 3·1% faster development and 2·1% larger size) without compromising offspring number. However, the former produced eggs that were slightly, albeit significantly, smaller when it fed on alternating hosts as compared with a preferred host. Moreover, host order affected reproductive performance in host generalists (e.g. 2·8% larger eggs when the first feeding was performed on a non-preferred host), but not in a host specialist. We conclude that immediate effects of environmental fluctuation on parasite fitness depend on the degree of host specialization.

We studied nestedness and its relationships with beta-diversity in flea communities harboured by three closely related rodent species (Rhabdomys pumilio, Rhabdomys intermedius, Rhabdomys dilectus) at two spatial scales (within and among host populations) in South Africa and asked (a) whether variation in species composition of flea communities within and among host populations follows a non-random pattern; if yes, (b) what are the contributions of nestedness and species turnover to dissimilarity (= beta-diversity) among flea communities at the two scales; and (c) do the degree of nestedness and its contribution to beta-diversity differ among host species (social vs solitary) and between scales. We found that nestedness in flea assemblages was more pronounced (a) in social than solitary host species and (b) at lower (among host individuals within populations) than at higher scale (among host populations). We also found that higher degree of nestedness was associated with its higher contribution to beta-diversity. Our findings support earlier ideas that parasite community structure results from the processes of parasite accumulation by hosts rather than from the processes acting within parasite communities.

We tested Szidat's rule (the more primitive the host, the more primitive the parasites it harbours) by analysing the relationships between phylogenetic clade ranks of fleas and their small mammalian hosts in four biogeographic realms (Afrotropics, Neotropics, Nearctic and Palearctic). From the host perspective, we tested the association between host clade rank and the mean clade rank of all fleas collected from this host. From the flea perspective, we tested the relationships between flea clade rank and the mean clade rank of hosts on which this flea was recorded. First, we tested whether the analysis of the relationships between host and flea clade ranks should be controlled for phylogenetic dependence among either host or flea species. Then, we tested for the associations between host and flea clade ranks separately for each realm using either a phylogenetic general least-squares analysis or an ordinary least-squares analysis. In all realms, the mean clade rank of fleas parasitic on a given host increased with an increase of this host's clade rank, and the mean clade rank of hosts recorded on a given flea increased with an increase of this flea's clade rank, suggesting that Szidat's rule, at least to some extent, holds for fleas.

We studied the structure of chigger mite (Trombiculidae) communities parasitic on a South African rodent, Rhabdomys pumilio. We aimed to determine whether: (a) different chigger species differ in preferences for certain body areas of a host and (b) chigger assemblages among body areas of the same host individual, are structured and if so, whether the structure of these assemblages is aggregative or segregative. Rhabdomys pumilio is parasitized by seven chigger species belonging to six genera. The three most abundant species (Leptotrombidium sp. nr. muridium, Schoutedenichia sp. and Neoschoengastia sp. A) displayed a non-random distribution across the host body, with the two most abundant species (L. sp. nr. muridium and Schoutedenichia sp.) significantly associated with the tail area. In addition, whenever non-randomness of chigger co-occurrence in the same body area was recorded, it indicated positive but not negative co-occurrences of different species. This might be due to similarity of chigger species in resource needs and strategies to avoid host defence efforts.

To understand mechanisms behind positive interspecific co-occurrences in flea infracommunities, we asked whether co-infestation results in an increase of flea fitness (quantity and/or quality of the offspring). We studied reproductive performance of Xenopsylla ramesis and Parapulex chephrenis when they exploited their characteristic host (Meriones crassus and Acomys cahirinus, respectively) either alone or together with another species. We used egg production, the number of new imagoes, pre-imaginal survival and egg size as fitness-related variables and predicted that fitness will be higher in fleas feeding in mixed- than in single-species groups. In both fleas, mean number of eggs produced per female flea did not depend on experimental treatment. No effect of single- vs mixed-species infestation on the mean number of new imagoes per female and the number of emerged imagoes per egg was found for X. ramesis, whereas both these numbers were higher in mixed- than in single-species groups for P. chephrenis. X. ramesis produced eggs of similar size independently of treatment, whereas eggs produced by P. chephrenis in mixed-species groups were significantly larger than eggs produced in single-species groups. We conclude that an increase in reproductive performance as a response to co-infestation may be one of the mechanisms behind aggregative structure of flea infracommunities. However, this response may vary among flea species.