Combining barcodes and genomics to study diversification: The case of the House Wren Troglodytes aedon

CAMPAGNA, LEONARDO; LIJTMAER, DARÍO A.; KOPUCHIAN, CECILIA; TUBARO, PABLO L.

Congreso; 7th International Barcode of Life Conference; 2017

Background: COI-based analyses using barcode libraries often discover divergent intraspecific lineages, which are frequently interpreted as having limited gene flow. However, to confirm this one should use nuclear markers, which are better suited for studying gene flow and can currently be obtained at large scale using genomic techniques. Here we combine mitochondrial and genomic data (ddRADseq) to study the evolutionary history of the House Wren, Troglodytes aedon, focusing on the southern cone of South America. Results: COI data from around 90 specimens from Argentina, Bolivia and Uruguay revealed the presence of at least 3 continental lineages with up to 5% divergence. These lineages, however, were not geographically structured: only one lineage is present in Patagonia but representatives from two or three different lineages can be found in particular localities in Northern and Central Argentina (i.e. lineages are largely sympatric in some areas). Our genomic analysis of thousands of markers did not differentiate these lineages and instead suggested high levels of gene flow among mitochondrial clades, with the sole exception of a few birds from Northern Bolivia. The subtle nuclear differentiation among mitochondrial lineages could be partially explained by isolation by distance. These results suggest the presence of divergent mitochondrial lineages in a largely panmictic population. This pattern could be due to ancient isolation by barriers that are no longer effective and/or the consequence of a widely distributed species with a very large effective population size that retains mitochondrial diversity. Significance: By showing contrasting mitochondrial and genomic patterns of diversification in a widespread passerine, this study highlights that analyzing nuclear and mitochondrial data together allows for a more complete understanding of evolutionary history. These results also emphasize the need for precaution when mitochondrial patterns are interpreted on their own in evolutionary analyses.