Meeting Abstract
Hormonal systems enable individuals to maintain homeostasis in the face of environmental challenges, linking environmental variability with variation in behavior and life history traits within an individual. Additionally, information about the environment can be conveyed by maternal hormones to influence offspring phenotypes. We take advantage of the adaptive radiation of the threespine stickleback fish, Gasterosteus aculeatus , to ask how environmental differences among populations influence this signaling process in eight populations from southcentral Alaska and southern British Columbia. In these regions, oceanic stickleback have repeatedly colonized freshwater habitats following the last glacial recession, permitting assessment of phenotype shifts from regional, oceanic ancestral surrogates to locally adapted freshwater forms. Here we evaluate natural variation in maternal cortisol and its effects on offspring characteristics. Plasma cortisol levels of ovulated, wild females were measured immediately post capture and an hour after a stressor. Clutches were split for measurement of cortisol and to fertilize for offspring production. Fry were reared under identical laboratory conditions across populations. We provide evidence of regional differences in maternal plasma, egg, and offspring cortisol levels, as well as fry growth and feeding performance. We examine possible reasons for regional differences in the plastic responses of hormone systems, transgenerational consequences of those responses, and the evolutionary trajectories under divergent selective regimes in the two regions.
