88.2 Friday, Jan. 6 Variation in the Glucocorticoid Stress Response and Behavior along a Gradient of Invasive House Sparrows (Passer domesticus) LIEBL, A.L*; GARRINGER, A.R.; WILEY, D.D; SIERRA, A.S.; MARTIN, L.B.; Univ. of S. Florida, Tampa, FL email@example.com
Many invasive species show extensive phenotypic variation among populations of different ages. With the short time in which invasions typically occur, genetic evolution is an unlikely explanation for these differences, particularly in recently introduced populations. Behavioral plasticity, which can be mediated by stress hormones (e.g. glucocorticoids; GCs), is a more likely driver of colonization success in many species. In fact, behaviors such as exploration, innovation, and neophobia have been correlated with invasion success. Few direct tests of behavioral plasticity have been conducted in a species undergoing range expansion, though. Here, we predicted populations at an invasion front would be most exploratory and innovative, and least neophobic. To mediate these changes, we expected a damped GC response to restraint at the invasion front and increased capacity for GC regulation. To test this, we caught house sparrows (Passer domesticus) from 8 cities in Kenya, the site of one of the most recent introductions of this species. House sparrows arrived in each city at different times, creating a gradient of established (60 yrs) to recently introduced (>5 yrs) populations. We measured behavioral variation by exposing individuals from each population to six behavioral tests. Additionally, we measured GC regulation by measuring baseline and restraint induced GCs as well as GC receptor density in the hippocampus. Contradictory to our hypothesis, individuals from established populations released more GCs in response to restraint. Receptor density and behavior analysis are still ongoing. The results of this study contribute to studies of invasion behavior as well as coping styles generally.