To be or not to be: the question of defining genera in the Old World Oraseminae (Hymenoptera: Eucharitidae)

Madagascar is a well-known hotspot for biodiversity as it contains some of the world’s most unique flora and fauna. Geologic and climatic history have likely sparked the evolution of Madagascar’s exclusive biota. Among the 5,800 invertebrates known to the island, there are a number of unique species of Eucharitidae (Hymenoptera: Chalcidoidea), a diverse family of specialized ant-parasitoid wasps. Beyond a few species descriptions, there has been little systematic study of Eucharitidae in Madagascar. Our research explores the diversity, distribution, phylogenetics, and biogeographic origins of Madagascan eucharitids. We review the known species of Madagascar and propose new species in two subfamilies, Oraseminae and Eucharitinae. Where these are placed depends on a justification of generic limits using the criterion of monophyly and morphological divergence from other recognized genera. We explore the origins and diversification of the family in the Old World using combined ribosomal and mitochondrial molecular data to construct parsimony, maximum likelihood and Bayesian phylogenies. We infer key evolutionary events using divergence dating analyses from fossil data from Baltic amber. Our results indicate multiple origins and rapid morphological divergence of Malagasy Eucharitidae from Afrotropical, Australian, and Oriental regions suggesting support for a Cenozoic dispersion hypothesis.