Contributions of temporal and spatial variation to the diversity of soil-dwelling testate amoeba assemblages in a swampy forest

Abstract

Understanding the spatial and temporal variation in protist communities is essential for comprehensive studies on diversity and biogeography, yet most research focuses on either spatial or temporal processes, ignoring their combined effects. Here we use an additive partitioning approach to estimate the contribution of temporal and spatial components to the total taxonomical (morphospecies) diversity of testate amoebae in a swampy forest (the forest-steppe zone, Russia) during a snow-free season (from April to November). Testate amoebae have been chosen as model organisms for the study because they are a diverse and abundant group of protists that play important roles in soil communities mostly as consumers in decomposer food webs. Our results indicate that seasonality considerably contributed to the variation in the total species richness (γ) of both live and empty shell assemblages of testate amoebae (48 and 38 %, respectively). The beta component of species richness related to the spatial variation among sampling plots explained 22 % of γ-diversity in live assemblages and 28 % in empty shell assemblages. Beta diversity (both as species richness and species composition) decreased towards the end of the snow-free season. Spring assemblages were dominated by hydrophilous species of testate amoebae, whereas xerophilic species were more abundant in autumn. Our results imply that the snowmelt phase could be an important factor setting the heterogeneity of testate amoeba assemblages in the early spring, whereas in the rest of snow-free season the assemblages were considerably controlled by substrate moisture. Overall, temporal sampling is essential for adequate estimates of species diversity of soil-dwelling testate amoebae.