Molecular systematics and evolutionary history of the genus Carabus (Col. Carabidae)

Despite the number of evolutionary, ecological and conservation studies that are conducted on Carabus, the global evolutionary history of the genus remains poorly understood. Here, we analysed 7.5 kilobases of DNA sequence data (six mitochondrial and four nuclear genes) from a worldwide sample of 45% of the known subgenera (99 species and 14 subspecies). We compared the nuclear and mitochondrial phylogenies obtained from Maximum likelihood and Bayesian analyses through topological tests of congruence and dating analyses. Our results mostly corroborate the monophyly of the morphological subgroups of Carabus. However, current morphological and molecular data appear unable to accurately infer the deep branchings within the genus. We show that Carabus originated ca. 16.7-25.1 Ma, approximately 25 Myr later than previously estimated. Major groups of Carabus are subdivided into clades that diverged from each other in a relatively short period of time around 10 Ma (6.6-14.8). This time frame suggests that the present-day distribution of Carabus subgroups may be explained by isolation resulting from Eurasian forest fragmentation brought on by Miocene climate changes and by mountain orogenesis. Finally, we highlight several conflicts between mitochondrial and nuclear topologies that may be explained by mitochondrial introgression.