Dispersal ability is associated with contrasting patterns of beta diversity in African small mammal communities

Aim: Spatial processes and environmental filtering are important factors shaping community composition, but their effects are rarely tested across all aspects and components of beta diversity. We investigate both of these factors to explain patterns of taxonomic, functional and phylogenetic beta diversity of small mammals across Sub-Saharan Africa. We predict that groups with poorest dispersal ability will experience the highest taxonomic and phylogenetic turnover but a nesting of functional diversity independent of dispersal. Location: Africa. Taxa: Rodents, bats, shrews. Methods: We amassed a continent-spanning dataset of 97 bat assemblages, 166 rodent assemblages and 153 shrew assemblages comprising a total of 183, 225 and 109 species, respectively, from six bioregions of Sub-Saharan Africa. We calculated three aspects of beta diversity: taxonomic, functional and phylogenetic. For each of these, we first calculated total beta diversity based on the Sørensen index (β_sor) and then decomposed this into turnover (β_sim) and nestedness (β_nes) components. We then used Moran's Eigenvector Maps to examine the relationships between each aspect of beta diversity and environmental gradients (environmental filtering) and geographical distance between sites (spatial processes). Results: We found consistent patterns across the three taxa in all aspects of beta diversity, with taxonomic beta diversity being greatest and phylogenetic beta diversity being lowest. The turnover component was typically greater than the nestedness component for taxonomic and functional beta diversity, but not for phylogenetic beta diversity, for all three groups. Beta diversity was also linked with the dispersal ability of the three groups, with the highest levels of beta diversity found in shrews, intermediate levels in rodents and the lowest levels in bats. Main Conclusions: Spatial processes, which are linked to the dispersal abilities of the three taxa of small mammal, dominate environmental drivers in structuring African small-mammal communities with phylogenetic comparisons suggesting a relatively permeable continent.