Meeting Abstract

68.1  Saturday, Jan. 5  The environmental and physiological factors modulating immunity in an opportunistic breeder SCHULTZ, EM*; HAHN, TP; Univ. of California, Davis

In order to be optimally suited to the current environment, organisms must choose when and how to allocate limited energy resources to the most essential physiological process. This conflict often results in a trade-off between investing in future survival (e.g., immune function) or current reproduction. Much research on these tradeoffs has focused on seasonally breeding organisms that constrain reproduction to times of year when environmental conditions are benign. In contrast, organisms such as the red crossbill Loxia curvirostra specialize on conifer seeds which are unpredictably available in space and time, and so have evolved temporally flexible reproductive schedules allowing them to reproduce 10 months a year if seeds are abundant. In this study we examined variation in allocation to three measures of constitutive innate immunity: differential white blood cell counts, hemolysis-hemagglutination and microbial killing assays. We compared those results between breeding and non-breeding individuals across seasons (summer, winter) and years of high and low food availability. In general, crossbills are able to invest more in both reproduction and immunity if environmental conditions are benign (summer, good cone crop). However, if environmental conditions are harsh (winter, poor cone crop), immunity tends to be lower, even in good cone years. Data collected from this summer (a poor cone year) will be used to augment prior data. Results from this study will provide novel information regarding environmental and physiological modulators of immunity in free-living animals, as well as providing a unique opportunity to investigate how harsh environmental conditions and reproductive effort may interact to shape investment patterns and life history evolution.