Meeting Abstract

P1.14  Saturday, Jan. 4 15:30  Stress hormone diminishes directional selection on call rate in the green treefrog DAVIS, A.G.*; LEARY, C.J.; Univ. of Mississippi; Univ. of Mississippi agdavis@go.olemiss.edu

There is growing evidence indicating that environmental stressors can influence mate choice by females but whether such effects are related to circulating stress hormone levels (e.g., glucocorticoids) remains largely unexplored. We examined the effects of circulating glucocorticoids on mate choice in female green treefrogs, Hyla cinerea. Specifically, we examined whether circulating corticosterone (CORT) level could alter preferences for call rate – an acoustic feature that is under strong directional selection via mate choice by females in most anuran species. Amplexed gravid females were captured in the field and either not treated, injected with saline only, or injected with 4, 8 or 16 μg of CORT in saline vehicle. Females were placed in an acoustic chamber 1 hr after treatment and phonotactic responses to broadcast conspecific calls that differed in call rate (2.5 vs. 1.25 calls/sec) were examined in a dual speaker playback design. Females that were untreated, injected with saline only, or injected with a low dose (4 μg) of CORT exhibited a preference for calls broadcast at a high rate. However, females that were injected with 8 or 16 μg of CORT exhibited a significantly greater probability of choosing calls broadcast at the low call rate. Our results thus indicate that CORT diminishes directional selection on call rate in this species. Such hormonally-mediated variation in female mate choice could influence signal evolution.