Phylogenetic patterns in regional flea assemblages from 6 biogeographic realms: strong links between flea and host phylogenetic turnovers and weak effects of phylogenetic originality on host specificity

Abstract

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.

Relationships between functional alpha and beta diversities of flea parasites and their small mammalian hosts

“…Another, not necessarily alternative, reason for the positive relationships between flea and host functional diversities may result from the tight relationship between flea and host phylogenetic diversities (Krasnov et al ., 2023 a ; but see Yaxley et al ., 2023 ) since many traits of both fleas and hosts are phylogenetically conserved. In fleas, phylogenetically conserved traits include, for example, body size (Surkova et al ., 2018 ), latitudinal position and size of geographic range (Krasnov et al ., 2018 a , 2018 b ) and characteristic abundance (Krasnov et al ., 2011 ), whereas in hosts, such traits include, among others, body size (Capellini et al ., 2010 ), relative brain mass (Antoł and Kozłowski, 2020 ) and dispersal distance (Whitmee and Orme, 2012 ).…”

“…We recognize that these explanations are highly speculative and warrant further investigation. Interestingly, environmental factors affecting flea beta diversity within a realm differed between functional (this study) and phylogenetic (Krasnov et al ., 2023 a ) beta diversities. This supports the recent ideas that (a) phylogenetic diversity might be an unreliable surrogate of functional diversity and (b) the relationship between phylogenetic diversity and functional diversity is context dependent (Yaxley et al ., 2023 ).…”

“…These data were averaged across 30 arc-second grids separately for each region. Sources of data on the latitudes and longitudes of the regions’ centres, as well on environmental variables, can be found elsewhere (Krasnov et al ., 2023 a ). Then, each category of environmental variables for each realm was subjected to principal component analyses, and the original values were subsequently substituted with the scores of the first principal components.…”

“…The resulting 3 composite environmental variables were a vegetation variable (reflecting the amount of green vegetation), an air temperature variable and a precipitation variable. These composite variables reflected an increase in the respective original variables (amount of green vegetation, air temperature and precipitation) and explained from 72 to 97% of the variation in the environmental factors (see details in Krasnov et al ., 2023 a ).…”

“…Studies that have dealt with the relationship between phylogenetic diversities of parasites and their hosts also demonstrated that geographic patterns of this relationship differed depending on the measure of diversity considered. Indeed, flea phylogenetic alpha diversity depended on the phylogenetic alpha diversity of their small mammalian hosts in the Palearctic only but not in the Nearctic, Neotropics or Afrotropics (Krasnov et al ., 2019 a ; see also Krasnov et al ., 2012 ), whereas a positive relationship between parasite and host phylogenetic beta diversity (Clark et al ., 2018 ) has been observed in 6 biogeographic realms (Krasnov et al ., 2023 a ).…”