Immune defence, dispersal and local adaptation

Abstract

To determine the influence of dispersal on the expression of immune traits, we conducted a reciprocal transfer experiment. Chorthippus biguttulus grasshoppers from two populations were released as juveniles into their native and transfer environments. After recapture as adults, we found that an immune trait, the amount of phagocytically active cells, was significantly reduced in the transfer environments. In contrast, adult body mass differed between the two habitats, but was not reduced in the transfer environments. The results suggest that dispersal to a new environment can reduce the expression of immune traits, while otherwise not influencing body condition. One reason for such an effect could be that the parasite community in the foreign environment might be relatively maladapted, which would lead to reduced demands for resource allocation to immune traits