Fine-scale genetic structure of two carabid species with contrasted levels of habitat specialization.

Using microsatellite markers, we compared the genetic structure of populations of two carabid species, one described as a generalist (commonly found in forest and in open habitats) and the other known as a forest specialist. Both species were sampled in the same forest plots, which were separated from each other by either open or forested areas. At the local scale considered (13.6 km separating the most distant plots), genetic differentiation was substantial for both species studied, but populations of the forest specialist Carabus punctatoauratus appeared to be more spatially structured than those of C. nemoralis. Isolation by distance analyses showed that nonforested areas are partial barriers to gene flow for both species studied, although more clearly for the forest specialist. Between and within forests, dispersal capacity of the generalist C. nemoralis was shown to be higher than that of the specialist C. punctatoauratus.