Ecological immunology of lestid damselflies: Explaining variation in immune defense against parasitic water mites

This thesis tests predictions of the emerging theory of ecological immunology using variation in immune expression of Lestes dryas Kirby, Lestes focipatus Rambur, Lestes unguiculatus Hagen and Lestes congener Hagen to a generalist parasitic water mite, Arrenurus planus Marshall. Immune responses of the four lestid species were compared as they relate to prevalence and intensity of mite infection; these measures of parasitism did not fully explain among-species variation. Within-species variation in immunity of L. forcipatus was related to time of season, but not to host body size or asymmetry, measures of host condition. When L. forcipatus were allowed to respond to Sepahdex beads at a fixed temperature across season, no seasonal pattern in immunity was observed and a positive correlation between condition and immune response in males was detected. These results implicate seasonal variation in temperature as being a major factor in determining immune responsiveness of lestid damselflies.