Secondary contact followed by gene flow between divergent mitochondrial lineages of a widespread Neotropical songbird (Zonotrichia capensis)

Abstract

Understanding how genetic and phenotypic differences that arise in geographically isolated populations influence the outcome of secondary contact advances our knowledge of speciation. In the present study, we investigate the secondary contact between divergent lineages of a widespread Neotropical songbird, the Rufous-collared sparrow (Zonotrichia capensis). Zonotrichia capensis is morphologically and behaviourally diverse, and shows a pattern of lineage diversification produced by a Pleistocene expansion and colonization of South America from a probable Central American origin. Consistent with previous results, we find three lineages throughout the species range, showing between 1.5% and 2.5% divergence in mitochondrial control region sequences. These lineages come into secondary contact in the Dominican Republic, La Paz (Bolivia), and North-eastern Argentina. We use DNA microsatellite data to study a broad secondary contact zone in North-eastern Argentina, finding that Bayesian clustering analyses do not assign individuals to their respective mitochondrial lineages. Overall, we did not observe nuclear genetic discontinuities in the study area. We conclude that, if genetic, morphological, and/or cultural differences accumulated among lineages during isolation, they were insufficient to prevent gene flow after secondary contact.