Specialization and habitat: spatial and environmental effects on abundance and genetic diversity of forest generalist and specialist Carabus species.

Habitat specialist species are supposed to be more susceptible to variations in local environmental characteristics than generalists. To test this hypothesis, we conducted a comparative analysis on abundance and genetic diversity of forest carabids differing in their habitat requirements. Four species were sampled in forests characterized by abiotic, landscape and biotic environmental variables. A statistical framework based on canonical correspondence analysis was used for one habitat generalist and one habitat specialist species to determine the relative contribution of environmental variables in structuring inter- and intrapopulational genetic diversity depicted by microsatellites. Our results showed that sympatric species differed in their sensitivity to environmental variables. The same variables were found to be important in analyses of abundance and genetic data. However, specialization was not related to a greater sensitivity to local environmental characteristics. The strong impact of spatial variables on genetic data suggested that genetic variation among populations would largely reflect the response of individual species to dispersal opportunities more than the effect of habitat quality.