Relationships between local and regional species richness in flea communities of small mammalian hosts: saturation and spatial scale

Abstract

The number of species coexisting in a community may be regulated by local factors (e.g., competitive interactions), or by regional processes (e.g., dispersal from a regional species pool). The relative importance of local and regional processes can be inferred from the shape of the relationship between local and regional species richness. We investigated this relationship in communities of fleas parasitic on small mammals at two spatial scales: between the richness of fleas on individual hosts (infracommunities) and that of fleas on host populations (component communities), and between the richness of component communities and that of the entire regional species pool. We tested linearity (proportional sampling) versus curvilinearity with an asymptote (species saturation) by plotting "local" against "regional" species richness of fleas either among host species or within host species among populations. At the two spatial scales, we found consistent curvilinear relationships between species richness of the more "local" communities and richness of the more "regional" communities. This was true across all host species in the data set and for geographic subsets, even after controlling for the influence of sampling effort on estimates of species richness, and that of host phylogeny in interspecific analyses. We also tested for density compensation in species-poor communities. There was no strong evidence for density compensation at the infracommunity level, although its existence at the component community level appeared likely. Our results suggest that identical patterns in local-versus-regional species richness observed on two different spatial scales arise via different mechanisms: infracommunities appear saturated with flea species most likely because of local processes, such as host immune defenses, whereas component communities are saturated with species through interspecific competition, possibly among larval stages.

Coevolution between multiple helminth infestations and basal immune investment in mammals: cumulative effects of polyparasitism?

“…Such variability may then induce too much statistical noise to successfully extract evolutionary signal. In order to minimize this risk, we have only retained studies for which helminth diversity was estimated at a regional scale (sensu Krasnov et al (2006)) for each mammal species. In fact, recent studies have highlighted that parasite diversity may be highly repeatable in mammals at this spatial scale (see Krasnov et al (2005) for fleas; Krasnov et al (2008) for gamasid mites; Bordes and Morand (2008) for helminths).…”

Drivers of symbiont diversity in freshwater snails: a comparative analysis of resource availability, community heterogeneity, and colonization opportunities

“…An extensive body of previous research has highlighted the diversity of parasites distributed among either among individual hosts within a region or between host species spanning distinct geographic regions (Guégan et al 1992; Kennedy and Bush 1994; Morand et al 2000; Guernier et al 2004; Hechinger and Lafferty 2005; Krasnov et al 2006; Dunn et al 2010; Poulin 2014; Johnson et al 2016). Nonetheless, identifying the drivers of symbiont at the more intermediate scales remains a major research priority, particularly at the population- to metacommunity scale at which diversity can be influenced by factors ranging from the species interactions, habitat heterogeneity, and especially by colonization opportunities (Ricklefs 2004; Cronin and Reeve 2005; Goater et al 2014).…”

Assessing species saturation: conceptual and methodological challenges

“…Finally, Krasnov et al . () analysed records of flea diversity on 28 small mammal species. In this study, the species pool was defined as all flea species present on a host species, i.e.…”