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J.1-4: Population genetics of American black ducks in coastal North Carolina

Presented by Daniel M. Lawson - Email: dlawso@udel.edu

North Carolina represents the southern extent of the American black ducks (Anas rubripes, hereafter, black duck) breeding range. Due to the presence of mallards (Anas platyrhynchos) on the breeding grounds and observed hybridization between the two species, we assessed genetic integrity, hybridization rates, and population structure of this local breeding population. Genomic and mitochondrial DNA was extracted from chorioallantoic membranes and contour feathers found at monitored nests and prepared for analysis using high-throughput DNA sequencing methods (ddRADseq). First, we tested for parentage and sibship across 40 North Carolina black ducks with the program COLONY. Next, nuclear and mitochondrial population structure, genetic diversity, and differentiation was assessed across samples, and across 290 genetically vetted mallards, black ducks, and mallard-black duck hybrids that served as genetic references. Despite a high level of interrelatedness among our samples , nucleotide diversity remains high (~0.0074), suggesting sufficient gene flow from other black ducks and/or mallards into the breeding North Carolina population. Interestingly, we are also able to confirm that two black duck sisters nested within 10 meters from each other, suggesting natal philopatry. Finally, we report a hybridization level of 45% (N =18), covering three filial generations. Of identified hybrids, ~47% (N = 8) were the result of game-farm mallard X black duck pairings. Thus, we conclude that due to high rates of interspecific hybridization and successive backcrossing events, introgression from wild and game-farm mallards is occurring into this population of breeding black ducks.
Session: Eastern Mallards & Brown Ducks (Friday, August 30,13:20 to 15:00)