Dissertation Research: Adaptive behavioral and physiological changes among populations undergoing range expansion

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Non-native species cause major ecological and economic damage in their introduced range; it is important to identify predictors of invasiveness to prevent future invasions. This information might also prove to be important is assessing the vulnerability of native species to environmental change. One of the most recent introduction events, the house sparrow (Passer domesticus) to Kenya, is still expanding beyond the site of initial introduction. Kenyan house sparrows do not have high genetic diversity, however still exhibit extensive behavioral and physiological variation; interestingly, the observed variation is correlated with the estimated age of the population. House sparrows closest to the edge of the range are more exploratory and release more stress hormones (glucocorticoids) in response to stressors than those closer to the site of initial introduction. However, what these trait differences mean in terms of fitness along the range expansion is unknown; further, how these differences arise given the lack of genetic diversity is also unknown. The goal of the present research is to determine A) if increased exploration and stress hormones grant a fitness advantage at the range edge, but a disadvantage in more familiar habitats; and B) whether these differences arise due to differences in maternal care during offspring development. To test these questions, observation of natural parental care as well as manipulattion of a mother's ability to provision during the nestling period in nestbox colonies will be carried out in Kenya. The PI predicts that increased exploration and stress hormones increase fitness at the edge of a range, but decrease it at the site of introduction. Further, it is also expected that food supplementation will generate offspring most like those naturally occurring at the site of introduction and a reduction of provisioning will produce offspring similar to those at the range edge. The proposed study will strengthen international collaborations and provide research opportunities for underrepresented minority STEM undergraduates.