Turnover and nestedness in subtropical dung beetle assemblages along an elevational gradient

Aim: We investigated changes in dung beetle beta-diversity components along a subtropical elevational gradient, to test whether turnover or nestedness-related processes drive the dissimilarity of assemblages at spatial and temporal scales. Location: An elevational gradient (200-1,600 m a.s.l.) of the Atlantic Forest in southern Brazil. Methods: We investigated the extent to which beta-diversity varied along the elevational gradient (six elevations) at both spatial (among sites at different elevations) and temporal (different months at the same site) scales. We compared both the turnover and nestedness-related dissimilarity of species and genera using multiple-site or multiple-month measures and tested whether these measurements were different from random expectations. Results: A mid-elevation peak in species richness along the elevational gradient was observed, and the lowest richness occurred at the highest elevations. We found two different groups of species, lowland and highland species, with a mixing of groups at intermediate elevations. The turnover component of beta-diversity was significantly higher for both spatial (i.e. elevational) and temporal changes in species composition. However, when the data for genera by site were considered, the elevational turnover value decreased in relative importance. Nestedness-related processes are more important for temporal dissimilarity patterns at higher elevation sites. Main conclusions: Spatial and temporal turnover of dung beetle species is the most important component of beta-diversity along the elevational gradient. High-elevation assemblages are not subsets of assemblages that inhabit lower elevations, but this relationship ceases when beta-diversity is measured at the generic level. Environmental changes across elevations may be the cause of the differential establishment of distinctive species, but these species typically belong to the same higher taxonomic rank. Conservation strategies should consider elevational gradients in case-specific scenarios as they may contain distinct species assemblages in lowlands vs. highlands.