Acoustic and morphological dataset of seven anuran populations of two species from highland forests in Northeastern Brazil

Highlands are of paramount importance to the study of evolution as they are frequently implicated in historical and ecological processes that generate and maintain biological diversity. In northeastern Brazil, sparse rainforest remnants are located in highlands north of the São Francisco River, generally surrounded by the dry and open landscape of the Caatinga biome. Earlier studies suggest that these forests acted as historical refuges to the rainforest fauna and flora, especially during the climatic cycles of the Pleistocene. However, it is still unclear whether populations distributed in distinct highlands experienced phenotypic differentiation as a result of adaptation to the environmental conditions of each forest remnant. In this study, we used two frog species with wide geographic distributions, Dendropsophus oliveirai, a habitat specialist which breeds in permanent ponds, and Physalaemus cuvieri, a habitat generalist which breeds in temporary and permanent lentic environments, as models to investigate the relationships between environmental variation, geographic, genetic, and body size distance with advertisement call variation among populations inhabiting different highlands. We hypothesized that call variation would be strongly influenced by local environmental conditions, as sound signals are frequently adapted to the transmission environment. Our results indicate that acoustic variation among P. cuvieri populations is strongly influenced by environmental variation and moderate by geographic distance. In D. oliveirai, the environment is also the most influential factor in acoustic variation, followed by genetic and morphological variation. Besides that, the association between environmental and geographic factors suggests an indirect effect of geographic distance on acoustic variation in both species through an environmental gradient and also in genetic traits of the habitat specialist species. We believe that selective processes and isolation possibly act together in driving interpopulational acoustic variation with habitat-specific species being more affected by the isolation in suitable habitats.