Interspecific competition affects genetic structure but not genetic diversity of Daphnia magna

Abstract

There are multiple forces structuring the genetic diversity of populations, and numerous studies have investigated the effects of the environment, space and stochastic processes. The effect of variation in interspecific interactions on genetic diversity and structure has rarely been assessed. Here, in a mescosm experiment, I studied clonal diversity and composition of the water-flea Daphnia magna in presence and absence of the sympatric interspecific competitors D. longispina and D. pulex. The results showed little effect of interspecific competition per se on clonal diversity of D. magna. Instead, the observed minimum population size was the most important factor for clonal diversity. But variation in interspecific competition had an effect on the clonal composition, and the presence of both interspecific competitors changed the clonal composition of D. magna. Thus, I conclude that interspecific competition had little effect on genetic diversity of D. magna but an evident effect on the genotypic composition, which may be important for the genetic diversity and structure on larger spatio-temporal scales. © 2011 Östman.