Turnover, richness difference and nestedness of rodent assemblages along the southern Andes elevation gradient

Abstract

Beta diversity in ecological communities can reflect adaptations of species to differences in climate, environmental characteristics and site history, as well as local ecological dynamics. These dissimilarities among communities may reflect different processes as species replacement and richness difference or nestedness, which can be generated by different factors. Assemblages in mountain regions are expected to exhibit high beta diversity due to sharp environmental variation and historical events promoting isolation. Diversity patterns of small mammals along elevation gradients in the southern dry Andes exhibit high richness among high elevations and a humped shape pattern for abundances. However, it is not clear how beta diversity changes along this gradient, or the processes involved in this variation. Here we aim to evaluate small mammal beta diversity patterns along the elevation gradient. Therefore, we decomposed beta diversity into spatial turnover, richness differences and richness differences as a result of nestedness. Assemblage structure variation was assessed qualitatively and quantitatively. Also, we evaluate the local contribution of beta diversity (LCBD) and species contribution to beta diversity, to identify priority conservation sites and species. Our results show contrasting patterns among qualitative and quantitative beta diversity components. The former was mainly explained by species turnover, while the latter showed a higher contribution of richness difference than species turnover. Most components of beta diversity decreased with elevation, except for abundance turnover that showed an opposite trend. Furthermore, LCBD was higher at lower and mid-elevation sites and exhibited a negative relationship with species richness and abundance.