The history of the Caatinga: exploring phylogeographic patterns and evolutionary processes in three amphibians with next-generation sequencing data

Abstract

The Caatinga is the least studied and protected biome in Brazil. Its most striking feature is the water deficit caused by long and intense dry seasons, for which the biota is highly adapted. Despite this general condition of dryness, abiotic factors vary regionally and associations between environmental conditions and distribution patterns of diversity suggest historic relationships and a role in diversification. Information on the history of the biome are scarce and local, but suggest interactions with adjacent biomes related to past climate changes. Paleoindicators indicate partial replacement of the Caatinga by rain forests in the Pleistocene, while niche palaeomodeling supports a fairly stable Caatinga for the same period. By gathering the available information, along with insights from a phylogeographic study we conducted with microsatellite markers and one endemic frog, we were able to better formulate alternative biogeographical scenarios, but we still lack a proper dataset to reliably evaluate the different diversification hypotheses. In this project we propose to collect and process a large number of markers for the three amphibian species targeted in the original project, using Restriction site-associated DNA sequencing (RAD-seq) in the Carstens laboratory, Ohio State University, United States. We expect to obtain ~1000 loci per species based in previous experience with the use of this sequencing technology. To deal with this amount of data we'll explore a new model-based approach to fit population genetic models using a diffusion approximation to the joint frequency allele spectrum (dadi). This model-based approach will enable us to test or rank the designed biogeographic scenarios. (AU)