The role of glaciations in the evolutionary history of a widely distributed Neotropical open habitat bird

Abstract

Aim: The Neotropics constitute the most biodiverse region of the world, yet its patterns of diversification and speciation differ among Neotropical areas and are not equally well understood. Particularly, avian evolutionary processes are understudied in the open habitats of temperate South America, where the role of glacial cycles is not clear. We analysed the evolutionary history of a Neotropical widespread bird species as a case study to evaluate its continental-scale patterns and processes of diversification, with a focus on Patagonia. Location: Open habitats of the Neotropics. Taxon: Vanellus chilensis (Aves, Charadriiformes). Methods: We obtained reduced representation genomic and mitochondrial data from the four subspecies of V. chilensis to perform a phylogenetic/phylogeographical analysis and study the evolutionary history of the species. We complemented these analyses with the study of vocalizations, a reproductive signal in birds. Results: The initial diversification event within V. chilensis, approximately 600,000 years ago, split a Patagonian lineage from one containing individuals from the rest of the Neotropics. We found considerable gene flow between these two lineages and a contact zone in northern Patagonia, and showed that genomic admixture extends to northwestern Argentina. Shallower divergence was detected between the two nonPatagonian subspecies, which are separated by the Amazon River. Vocalizations were significantly different between the two main lineages and were intermediate in their temporal and frequency characteristics in the contact zone. Main Conclusions: Patagonian populations of V. chilensis are clearly differentiated from those of the rest of the Neotropics, possibly as a consequence of Pleistocene glaciations. A secondary contact zone in northern Patagonia with extensive gene flow among lineages appears to be the consequence of post-glacial, northward expansion of the Patagonian populations. Future analyses focused on the dynamics of the contact zone will allow us to establish whether the species continues to diverge or is homogenizing.