A Genetic Wallace's Line Across Wyoming - Genetic Structure of North American Rosy Finches

Abstract

North American rosy-finches (genus Leucosticte ) are cunently classified by the American Ornithologists' Union (1998) as three species - the Brown-capped Rosy-Finch, L. australis, with a breeding range largely restricted to the Colorado Rockies, but extending barely into southeast Wyoming and northern New Mexico, the Black Rosy-Finch, L. atrata, breeding from Utah north through western Wyoming (including GTNP) and west to Idaho and Nevada, and the Gray-crowned Rosy-Finch, L. tephrocotis, breeding from the Sierra Nevada through the Cascades and from northern Montana through the Rockies to Alaska. Based on previous results for a surprising genetic break for black bears (Ursus americanus) across Wyoming, I was interested in the degree of genetic differentiation among populations of rosy-finches, particularly between Brown-capped Rosy-Finches in Colorado and Black Rosy-Finches in Wyoming. Because the mating system is largely unknown, and because of reports in the literature of highly male-biased sex ratios (e.g., 6 males per female; French, 1959), I was also interested in using genetic markers to assess patterns of parentage in rosy-finches. Because of its striking plumage (often indicative of strong sexual selection) I was particularly interested in the Black Rosy-Finch. Using polymorphic microsatellites (nuclear DNA) we have now analyzed an initial sample of individuals from the three North American forms, including three sets of nestling Black Rosy­ Finches and the behavioral father at one of the nests.