Glucocorticoids, acoustic communication and sexual selection in treefrogs

January 3 – Febuary 28, 2021

Meeting Abstract

S9-12  Wed Jan 6 18:30 – 19:00  Glucocorticoids, acoustic communication and sexual selection in treefrogs Leary, CJ; University of Mississippi

Despite evidence that elevated glucocorticoids (GCs) can reduce investment in reproductive behaviors and growing interest in understanding how the stress response relates to fitness, there has been little emphasis on the role of GCs in sexual selection. I will discuss ongoing research in my lab examining the role of GCs in intra- and intersexual selection in the green treefrog, Hyla cinerea. In this species, males competing for mates engage in vocal contests using distinct amplitude-modulated aggressive signals. We have shown that hearing these calls can increase circulating levels of GCs in other males, especially small males that characteristically lose aggressive contests. Acoustic modulation of GC levels during male interactions, in turn, alters temporal aspects of male advertisement calls. For example, GC administration results in a rapid decrease in the duration of male advertisement calls and vocal effort. I show that these GC-mediated effects on vocal attributes are evident in natural populations i.e., circulating GC levels explain a significant proportion of the variation in the calls of chorusing males. I will present results from recent phonotaxis experiments showing that GC-mediated effects on the characteristics of male advertisement calls have a significant impact on mate choice by females, with females showing strong preferences for the calls of males with low GC levels. I will then present results showing that the strength of female preferences for male call characteristics may be contingent upon circulating GC levels, with weaker preferences exhibited by females with high GC levels. Together, these findings indicate that GCs can play a major role in both intra- and intersexual selection. I will discuss these findings in the context of selection on the stress response.

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