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 investigated the distance-decay pattern (an increase in dissimilarity with increasing geographic distance) in regional assemblages of fleas and their small mammalian hosts, as well as their ...interaction networks, in four biogeographic realms. Dissimilarity of assemblages (βtotal) was partitioned into species richness differences (βrich) and species replacement (βrepl) components. Dissimilarity of networks was assessed using two metrics: (a) whole network dissimilarity (β
WN
) partitioned into species replacement (β
ST
) and interaction rewiring (β
OS
) components and (b)
D
statistics, measuring dissimilarity in the pure structure of the networks, without using information on species identities and calculated for hosts-shared-by-fleas networks (Dh) and fleas-shared-by-hosts networks (Df). We asked whether the distance-decay pattern (a) occurs among interactor assemblages or their interaction networks; (b) depends on the network dissimilarity metric used; and (c) differs between realms. The βtotal and βrepl of flea and host assemblages increased with distance in all realms except for host assemblages in the Afrotropics. βrich for flea and host assemblages increased with distance in the Nearctic only. In networks, β
WN
and β
ST
demonstrated a distance-decay pattern, whereas β
OS
was mainly spatially invariant except in the Neotropics. Correlations of Dh or Df and geographic distance were mostly non-significant. We conclude that investigations of dissimilarity in interaction networks should include both types of dissimilarity metrics (those that consider partner identities and those that consider the pure structure of networks). This will allow elucidating the predictability of some facets of network dissimilarity and the unpredictability of other facets.
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.
Epidemiological studies worldwide have reported a high prevalence and a great diversity of Bartonella species, both in rodents and their flea parasites. The interaction among Bartonella, wild ...rodents, and fleas reflects a high degree of adaptation among these organisms. Vertical and horizontal efficient Bartonella transmission pathways within flea communities and from fleas to rodents have been documented in competence studies, suggesting that fleas are key players in the transmission of Bartonella to rodents. Exploration of the ecological traits of rodents and their fleas may shed light on the mechanisms used by bartonellae to become established in these organisms. The present review explores the interrelations within the Bartonella-rodent-flea system. The role of the latter two components is emphasized.
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.
We investigated the role of environmental filtering as an underlying mechanism of assembly of compound communities of fleas parasitic on Palearctic small mammals at two spatial scales; a continental ...scale (encompassing regions across the entire Palearctic) and a regional scale (across sampling localities within Slovakia). We used the three-table ordination (the RLQ analysis) and its extended version that links species occurrences with geographic space, environmental variables, and species traits and phylogeny (the ESLTP analysis). We asked whether environmental filtering acts as an assembly rule of compound communities of fleas and, if yes, a) whether the effect of environment on species composition of compound communities of fleas differs between spatial scales and b) what are the relative importance of the abiotic and host environments. We found that compound communities of fleas are, to a great extent, assembled via environmental filters that represent interplay between filtering via abiotic environment and filtering via host composition. The relative importance of these two components of environmental filtering differed between spatial scales. Host composition had a stronger effect on flea assembly than abiotic environment on the continental scale, while the opposite was true for the regional scale. The likely reason behind this scale-dependence is that communities on the regional scale are mainly governed by ecological and epidemiological processes, while communities on the continental scale are mainly affected by evolutionary, biogeographic and historical forces.
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•Phylogenetic nestedness of a host spectrum followed its compositional nestedness in some, but not other, flea species.•Compositional nestedness of a host spectrum is generated by ...similar mechanisms in many flea species.•Compositional nestedness of a host spectrum may be simultaneously driven by different mechanisms in the same flea.•Mechanisms generating phylogenetic nestedness of a host spectrum differ between flea species.
We investigated compositional and phylogenetic nestedness in the host assemblages of 26 host-generalist fleas across regions within the Palearctic. We asked the following questions: (i) are host assemblages exploited by a flea species compositionally or phylogenetically nested (=C-nested and P-nested, respectively) across regions?; (ii) if yes, what are the processes that generate nestedness, and does phylogenetic nestedness follow the same processes as compositional nestedness?; and (iii) are the biological traits of a flea species associated with its host assemblages’ degree of nestedness? Nestedness was calculated for matrices with rows ordered either by decreasing region area (=a-matrices) or increasing distance from the centre of a flea’s geographic range (d-matrices). Significant C-nestedness was found in either a- (three fleas) or d-matrices (three fleas) or both (10 fleas). Significant P-nestedness was detected in either a- (three fleas) or d-matrices (four fleas) or both (two fleas). In some but not other species, P-nestedness followed C-nestedness. The probability of C-nestedness to be significant, as well as its degree for d-matrices, was associated with a flea’s morphoecological traits, whereas this was not the case for either a-matrices or the P-nestedness for either type of ordered matrices. We conclude that compositional, but not phylogenetic, nestedness is (i) generated by similar mechanisms in many flea species and (ii) may be simultaneously driven by different mechanisms in the same flea. In contrast, mechanisms promoting phylogenetic nestedness differ between flea species and seem to act separately.
We investigated the associations between ecological (density, shelter structure), morphological (body mass, hair morphology) and physiological traits (basal metabolic rate) of small mammals and ...ecological (seasonality of reproduction, microhabitat preferences, abundance, host specificity) and morphological (presence and number of combs) traits of their flea parasites that shape host selection processes by fleas. We adapted the extended version of the three‐table ordination and linked species composition of flea assemblages of host species with traits and phylogenies of both hosts and fleas. Fleas with similar trait values, independent of phylogenetic affinities, were clustered on the same host species. Fleas possessing certain traits selected hosts possessing certain traits. Fleas belonging to the same phylogenetic lineage were found on the same host more often than expected by chance. Certain phylogenetic lineages of hosts harbored certain phylogenetic lineages of fleas. The process of host selection by fleas appeared to be determined by reciprocal relationships between host and flea traits, as well as between host and flea phylogenies. We concluded that the connection between host and flea phylogenies, coupled with the connection between host and flea traits, suggests that the species compositions of the host spectra of fleas were driven by the interaction between historical processes and traits.
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•In mammal-flea interaction networks, the phylogenetic signal for mammals was stronger than for fleas.•The phylogenetic signal for hosts, but not for fleas, was environmentally ...structured.•The phylogenetic diversity of hosts and fleas was not associated with the phylogenetic signals in interaction networks.
The structure of ecological interaction networks is associated with evolutionary histories of the interacting species. This is reflected by the phylogenetic signals (PS) in these networks when closely related species interact with similar partners because some traits inherited from the ancestors may determine ecological interactions. We investigated PS for small mammalian hosts and fleas in 80 regional interaction networks from four biogeographic realms (the Palearctic, the Nearctic, the Afrotropics, and the Neotropics). We asked (i) whether the relative strength of PS in host-flea networks is similar between hosts and fleas and/or between realms; (ii) how environmental variation affects the PS of hosts and fleas in their interaction networks; and (iii) whether the PS for hosts or fleas is affected by the phylogenetic diversity of either hosts or fleas, respectively. We found that the PS for hosts was stronger than that for fleas in all realms. An environmental effect on the PS for hosts, but not for fleas, was found in three of the four realms (except the Neotropics). In the Palearctic and the Nearctic, a stronger PS was characteristic for cooler and/or drier regions, whereas the opposite was the case for the Afrotropics in regard to precipitation. The phylogenetic diversity of regional host and flea assemblages was not associated with the values of the respective PS in any realm. We conclude that the pattern of the relative strength of the PS for hosts and fleas in their interaction networks is similar in different biogeographic realms with vastly different host and flea faunas. However, the environmental effects on the PS are geographically variable and might be associated with the history of host-flea associations, as well as the spatial pattern of environmental variation, within a realm.
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•Species from the regional pool that may inhabit a locality but are absent from it constitute dark diversity.•Dark diversity of flea assemblages of the same host across regions was ...affected by environmental factors.•Flea dark diversity of a host species within a region was affected by the degree of host sociality and structure of its shelter.•There was no association between flea dark diversity of a host and its phylogeny.
An assemblage of species in a locality comprises two components, namely (i) species that are present (realised diversity) and (ii) species from the regional pool that may potentially inhabit this locality due to suitable ecological conditions, but that are absent (dark diversity). We investigated factors affecting the dark diversity of component communities of fleas parasitic on small mammals in the northern Palearctic at two scales. First, we considered the dark diversity of flea assemblages of the same host (for 13 host species) across regions and tested for the effects of environmental factors and the number of available host species on the dark diversity of within-region flea assemblages. Second, we considered the dark diversity of fleas across host species within a region (for 20 regions) and asked whether within-host dark diversity is associated with host phylogeny and/or traits. We found that the dark diversity of flea assemblages harboured by small mammals varied substantially (i) within the same host species across space (in 12 of 13 host species) and (ii) between host species within a region (in eight of 20 regions). The size of the dark diversity of flea assemblages of the same host across regions was generally affected by environmental factors (mainly by the amount of green vegetation), whereas the size of the dark diversity of flea assemblages of a host species within a region was affected by host traits (mainly by the degree of host sociality and the structure of its shelter and, to a lesser degree, by its geographic range size) but was not associated with host phylogenetic affinities. We conclude that application of the dark diversity concept to parasite communities across space or hosts allows a better understanding of the factors affecting the species richness and composition of these communities.
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