Estrutura populacional intraespecífica e diversidade genética de Osteocephalus taurinus (Anura: Hylidae) no interflúvio Purus-Madeira, Amazônia Central

Abstract

The Amazon rainforest is the most biodiverse biome in the world, where amphibians are one of the biological groups with the highest levels of cryptic diversity reported across taxa. Despite noticeable efforts, processes driving differentiation among populations and speciation remains largely unknown in this biome, especially based on dense sampling over refined scales. We studied the population structure and genetic diversity of the Manaus slender ledged tree frog, Osteocephalus taurinus, along a geographic gradient of approximately 900 km. Using molecular markers including mitochondrial and nuclear genes, and microsatellites, we estimate the phylogenetic relationships, population structure, and patterns of intraspecific genetic variation and geographic differentiation through the study area. Our data recovered six genetic groups: two corresponding to O. taurinus and O. oophagus from its type locality, Reserva Ducke, at northern of Amazonas River. The third group corresponds to an O. taurinus population isolated at right bank of upper Madeira River. However, evidence for restricted gene flow was detected along the upper Madeira River. Within Purus-Madeira interfluve, the remaining three O. taurinus populations replace each other latitudinally along geographical and environmental gradients, with two contact zones identified. One contact zone is concordant between mitochondrial and nuclear DNA and corresponds to an ecotone region between closed- open rainforests. Following the riverine barrier hypothesis, natural selection by means of genetic drift is expected to cause differentiation among populations by large Amazonian rivers as vicariant barriers. Within continuous forested regions, abrupt transitions on gene frequencies are suggestive of narrow contact or tension zones. In those areas, selection is expected to be favored by local adaptation to different environmental conditions, given selection against dispersing migrants from immediate but environmentally distinct regions and against hybrids.