Life history and immune defense in two garter snake ecotypes II - A common garden experiment.

PALACIOS, M. G.; SPARKMAN, A. M.; BRONIKOWSKI, A. M.

Seattle, Washington, EEUU

Congreso; Annual Meeting of the Society for Integrative and Comparative Biology.; 2010

Society for Integrative and Comparative Biology.

Recent ecoimmunological theory proposes a link between pace of life and immune defense, such that fast-living species/populations are predicted to rely more on innate immunity (and less on acquired immunity) than slow-living ones. We previously found support for this prediction in two life-history ecotypes of the garter snake, Thamnophis elegans. Fast-living snakes that live in lakeshore habitats have higher levels of natural antibodies, complement-mediated lysis, and bactericidal competence (all measures of innate immunity) than slow-living snakes that live in meadow habitats. In this study, we conducted a common garden experiment to test whether the observed differences in immune defense between ecotypes are fixed (under genetic control) or are mainly plastic responses to different environmental conditions in lakeshore and meadow habitats. Wild-caught gravid dams were brought into the lab, gave birth, and their offspring were raised in a common environment. Four-month- old snakes reflected their original habitat immune phenotype for natural antibodies and complement activity, with lakeshore snakes having higher levels of both immune measures. These differences, however, were no longer detected when the snakes were measured at sixteen months of age. Bactericidal competence (measured only at sixteen months) did not differ between ecotypes. Our results suggest that differences in immune activity at an early age are due to maternal effects that disappear after several months in a common environment. Thus, the observed variation in immune defense between these two life-history ecotypes seems to be a plastic response to environmental factors. We discuss these results in the light of differences in temperature and food availability between the lakeshore and meadow habitats.