Phylogeographic structure suggests environmental gradient speciation in a montane frog from the northern Andes of Colombia

摘要

Allopatric speciation has been posed as the main mechanism affecting amphibian diversification. In contrast, the role of alternative mechanisms such as ecological speciation has received less attention, and empirical evidence of this mechanism in shaping species richness gradients remains elusive in the tropics. Highly heterogeneous landscapes can favor both allopatric and ecological speciation either by producing physical barriers to dispersal or by inducing selective pressures on lineages distributed along environmental gradients (e.g., climatic gradients). Based on explicit predictions under the ecological speciation hypothesis, we tested whether the phylogeographic, acoustic, morphological, and climatic features differ across the range of Pristimantis viejas, a frog species distributed along a wide altitudinal gradient in the northern Andes of Colombia. In agreement with our predictions, we found two highly differentiated lineages within P. viejas, showing striking differences in molecular diversity, acoustic, and climatic distribution. Importantly, we found that variation of such characteristics is highly congruent with variation in elevational ranges of these two lineages (P. viejas distributed in the lowlands and a cryptic sister lineage distributed in the highlands), and our evidence suggest that the divergence of these lineages was influenced by temperature-related variables. These results support a temperature-driven speciation process which may influence the amphibian diversity patterns in tropical mountains. Last, we describe and name the new cryptic lineage distributed in the highlands. We highlight that an integrative framework in phylogeographic studies should not only focuses on the identification of hidden lineages and their associated processes but also, when multiple lines of evidence are available, it should conduct to their formal description as species are the units for multiple biodiversity disciplines.