Three parallel radiations of Canthonini dung beetles in Madagascar

摘要

Madagascar has an exceptionally large fauna of more than 250 species of endemic dung beetles. Based on molecular phylogenies, the species descend from eight independent overseas colonisations, of which four have given rise to big radiations. Here, we analyse the tribe Canthonini with three parallel radiations following the respective colonisations at 64-44. Mya (Arachnodes-Epilissus, 101 species), 30-19. Mya (Epactoides, 37 species), and 24-15. Mya (Apotolamprus-Nanos, 61 species). All three radiations have taken place in forests, but there are also substantial differences between them. The oldest radiation exhibits the greatest ecological diversification, including monophyletic groups of primate and cattle dung specialists and multiple shifts to arboreal foraging. Analysis of pairs of sister species suggests allopatric speciation in the oldest and the youngest, apparently non-adaptive, radiations, whereas in Epactoides closely related species have diverged ecologically and have largely overlapping geographical ranges, suggestive of adaptive radiation in parapatry or regional sympatry.