Human-induced range expansions result in a recent hybrid zone between sister species of ducks

Datasets include mtDNA and nuclear sequences in fasta and VCF file formats, respectively, as well as plink files used in population genetics study of two sister species of ducks, mottled (Anas fulvigula) and Mexican (A. diazi) ducks. Specifically, despite being non-migratory, both species are increasingly being recovered outside their formal ranges, with the northeastward and westward expansions of Mexican and mottled ducks, respectively, perhaps resulting in secondary contact today. We assessed genetic ancestry using thousands of autosomal loci across the ranges of both species, as well as sampled Mexican- and mottled-like ducks from across overlapping regions of south Texas. First, we confirm that both species are indeed range expanding, with genetically pure western Gulf Coast mottled ducks confirmed as far west as La Salle county, Texas, while Mexican ducks were recovered across Texas counties near the USA-Mexico border. Importantly, the first confirmed Mexican x mottled duck hybrids were found in-between these regions that likely represents a recently established contact zone that is on average ~100 km wide. We posit that climate- and land use- associated changes, including coastal habitat degradation coupled with increases in artificial habitat in interior regions of Texas are facilitating these range expansions. Consequently, continued monitoring of this recent contact event can serve to understand species’ responses in the Anthropocene, but also be used to revise operational survey areas for mottled ducks.