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

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 analyzed
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/phylogeographic 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 non-Patagonian 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.