Rivers, Environment, and Climate: Shaping an Oven Frog's Evolution in the Chaco and Pampa Lowlands of South America

ABSTRACT Aim Pleistocene climatic oscillations induced climatic, environmental, and eustatic changes in the Chacoan‐Pampean Plain (CPP), profoundly impacting species' distribution, genetic diversity, population dynamics, and lineage diversification. Herein, we investigated how riverine barriers, landscape, and climate influenced the distribution and diversification of frogs of the South American lowlands. Location The mid‐latitude South American plains, including the Chaco and the Pampa biomes. Taxon Oven frog Leptodactylus latinasus . Methods We used mitochondrial sequences and genome‐wide SNP data throughout the species' distribution to assess population structure, infer phylogenetic relationships, and estimate divergence times. Also, we implemented spatially explicit models, demographic analyses, and tested alternative hypotheses of isolation and migration. We used ecological niche modelling (ENM) to reconstruct changes in geographical distribution and potential ancestral areas. Results We detected strong intraspecific phylogeographic structure, with significant breaks coinciding with interglacial periods, while cold phases were associated with bottlenecks and secondary contact events. We observed an intergradation zone between the Paraná River and the Chacoan‐Pampean biome limit, supported by significant bidirectional gene flow between nuclear groups. Main Conclusions Our findings highlight the effects of the climatic fluctuations on population dynamics and lineage divergence, the role of the Paraná River as a semipermeable barrier, the Chaco‐Pampa ecotone as an environmental barrier, and the influence of sea level changes on lineage isolation and connectivity. The biogeographic pattern and divergence times of L. latinasus are concordant with the diversification of other frogs co‐occurring in the CPP.