Meeting Abstract

P2.30  Monday, Jan. 5  Phenotypic integration of testosterone-mediated characters across distinct subspecies of the Dark-eyed Junco BERGEON BURNS, C.M.*; CAIN, K.E.; KETTERSON, E.D.; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington cbergeon@indiana.edu

Male dark-eyed juncos (Junco hyemalis) vary in how much they elevate testosterone (T) in response to a standardized injection of gonadotropin releasing hormone (GnRH). Responses to a GnRH challenge are repeatable across individuals and co-vary with significant phenotypic characters, including aggression and ornamentation (tail white). However, the question of whether such patterns are preserved as species diverge remains unanswered, as few studies have attempted direct comparisons of hormone-phenotype relationships across populations. If these relationships are highly integrated, we would expect similar patterns, but if hormone signal and hormone response evolve independently we might not. The white-winged junco (J. hyemalis aikeni) is a subspecies of dark-eyed junco endemic to the Black Hills of South Dakota. It is the largest of 15 named junco subspecies and the most highly ornamented. We asked whether hormone-phenotype relationships already identified within a population of Carolina junco (J. hyemalis carolinensis residing in Virginia) would generalize to the white-winged junco, and whether the responses would be stronger in this more ornamented population. During 2007 and 2008, we captured, measured, and administered GnRH challenges to breeding male white-winged juncos. We found similar within-population relationships between T and phenotype, suggesting generalizability. We also found greater elevation of T in response to GnRH in the white-winged junco as we had predicted. Our findings suggest stable hormone-phenotype relationships across populations maintained at least in part by variation in hormone signal, thus supporting the hypothesis of phenotypic integration.