Professor University of Bergen Bergen, Hordaland, Norway
The origin of the Malagasy insect fauna is poorly known but likely initiated by rare overseas dispersal, primarily from the African mainland. Due to a historical shift in the direction of wind and water currents after northward drifting of the Madagascar plate during the Oligocene, it has been argued that colonization from Africa to Madagascar should be older than Miocene age and that more recent faunal interchange has occurred mainly from Madagascar to the mainland. Based on molecular phylogenetic analyses of sixteen beetle lineages, we reconstructed the ancestral distribution and approximate age for colonizing Madagascar and eventually the return and seeding of new lineages on the African mainland. While nine lineages on the island are older than 50 Ma, many others arrived during the last 20 Ma. Dispersal back to the mainland occurred in eight of these lineages, both the Paleogene and Neogene, indicating that historical wind and water current systems were not as important as theory may suggest. Furthermore, the frequent recolonization of the mainland generated an increased overall diversity and illustrates how the island function as a diversification agent in the Afrotropics.