Meeting Abstract

S3.2  Sunday, Jan. 4  Hormones and life history evolution HAU, M; Max Planck Institute for Ornithology, Germany mhau@orn.mpg.de

Steroid hormones have pleiotropic effects on behavior, physiology and morphology. They also regulate major transitions between phases of the annual cycle in animals. These actions make steroid hormones ideal candidates for mediating life history trade-offs, such as the one between investment in fecundity versus self-maintenance. Intraspecific studies have supported such a role for both corticosterone and testosterone in avian species. We conducted an interspecific comparison of corticosterone and testosterone concentrations in free-living males from various passerine species living in a temperate or a tropical site. Species included in this study varied in life history strategies (annual adult survival rates; breeding season lengths) and body sizes. Breeding season length and survival rates explained most of the variation in baseline corticosterone, whereas maximal stress-induced corticosterone concentrations were best explained by body mass and survival rate. Breeding season length contributed strongly to explaining variation in testosterone concentrations. These data support the hypothesis that these two hormones are part of the physiological system that underlies avian life history strategies. We will discuss these findings in the context of hormone evolution.