Body size and genetic variation in the White-tipped Plantcutter (Phytotoma rutila: Cotingidae) suggest ecological divergence across the Chaco–Andes dry forest belt

Abstract

Dry forests characterize many of the biomes of southern South America and the Andes, such as the Chaco and the inter-Andean valley forests, which form a continuous belt (Chaco–Andes dry forest belt). Some of the taxa that inhabit this forest belt present genetic and phenotypic differentiation between edges of the region, which suggests the action of divergent evolutionary processes between forests (i.e., parapatric divergence). In order to test this hypothesis, we studied the morphological and phylogeographic variation of the White-tipped Plantcutter Phytotoma rutila (Cotingidae) and evaluated predictions of genetic and morphological evolutionary processes (e.g., local adaptation). The results supported that the environmental gradient along the Chaco–Andes dry forests might be promoting diversification because we found that body size of the White-tipped Plantcutter varied according to a step cline related to altitude, and thus parapatric processes might be responsible for this pattern. There are other taxa co-distributed across the study region presenting similar patterns of geographic variation, which suggests the action of concerted evolutionary phenomena in the Chaco–Andes dry forest.