Phylogeographic patterns in Leptodactylus troglodytes (Anura, Leptodactylidae) bring new insights to the history of the Caatinga

Leptodactylus troglodytes is a Caatinga associated anuran, also occurring at the northeastern part of the Cerrado savannas. In this study we examine genetic structure and population demographic history throughout this distribution. We sampled the nuclear genome at ~14,000 loci for 159 samples from 61 localities with RAdseq. Additionally, we included six other Leptodactylus species as outgroups to investigate biogeography of the South American dry diagonal. Leptodactylus troglodytes is more closely related to morphologically divergent but geographically proximate species (L. caatingae and L. cf. fuscus) than to the similar L. bufonius at the Chaco, suggesting convergence. In L. troglodytes, estimates of population structure vary from three to nine populations, but incorporation of geography resulted in three main populations occupying i) the Caatinga biome north of the São Francisco River, ii) the Caatinga biome south of the São Francisco River, and iii) the northeastern Cerrado. Admixtured individuals are especially abundant at the Cerrado-Caatinga ecotone and near the São Francisco river mouth. Estimates of population size through time suggest independent demographies for the three populations, varying from expansion to retractions occurring at different epochs. Taken together, genetic structure and demography support geographic distance, past climate changes and current/ past geographic barriers as major factors influencing the evolutionary history of this species.