Anuran altitudinal distribution in an Atlantic Forest hill: band area and Rapoport effect driving it

We evaluated how anuran species richness and composition changed along altitude, whether species distribution was consistent with predictions of the mid-domain effect, Rapoport effect and the possible existence of Rapoport rescue effect. Our study was conducted in the Salto Morato Natural Reserve, southern Brazil, between February 2013 and August 2015. We sampled anurans in sites between 25–918 m a.s.l. using Visual Encounter Surveys method. We ran simple linear regressions to evaluate altitude and band area effects on species richness and the species turnover along altitudinal gradient estimating beta diversity. We used cluster analysis to show those most similar altitudinal bands in species composition. We tested whether Rapoport effect explained species altitudinal variation, by simple linear regression between altitudinal range and the midpoint range of each species. We compared anuran species richness with that expected by the mid-domain effect, by simple linear regression determining whether species richness predicted by this effect was adjusted to empirical richness. We recorded 41 anuran species. Anuran species richness decreased in a linear fashion with increasing altitude and increased as the area of the altitude band increased. Anuran species turnover increased with distance among altitudinal bands. Similarity analysis indicated the existence of two primary groups. There was a significant relationship between species’ altitudinal range and midpoints, as predicted by Rapoport effect. There was no significant relationship between anuran species richness and that predicted by the mid-domain effect. This study contributed for the understanding of the anuran species distribution altitudinal effects in the Atlantic Forest biome and other areas and reinforced the tendency for a reduction in species richness with increasing altitude. Keywords: amphibian, elevational gradient, mid-domain effect, rainforest, Rapoport rule