The response of life‐history traits to a new species in the community: a story of Drosophila parasitoids from the Rhône and Saône valleys

In the present study, we investigated the evolution of life‐history traits in the main species of a community, after the arrival of a new competitor. Two parasitoid species, Leptopilina heterotoma and Asobara tabida, are present throughout the Rhône and Saône valleys, whereas a third species, Leptopilina boulardi, is slowly extending its distribution northwards. In the presence of L. boulardi, competing parasitoids experience a higher mortality and lower host availability. Resources should thus be re‐allocated between traits according to these new factors. We compared life‐history traits of populations of L. heterotoma and A. tabida in areas with and without L. boulardi. As predicted by both Price's balanced mortality hypothesis and the theory of life‐history traits, we found that investment in reproduction is higher in southern populations for both native species, coupled with higher travelling abilities. However, only A. tabida paid their higher fecundity by a lower longevity. The absence of a clear trade‐off between these traits in L. heterotoma may be explained by a lower metabolic rate in southern populations. These results highlight the importance of the community change over climate in the evolution of life‐history traits in this parasitoid community. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.