A multilocus approach to explore the phylogeny of a mega-diverse taxon: the case of Hycleus (Coleoptera, Meloidae)

Molecular phylogenetic studies involving mega-diverse genera represent a major challenge in systematics. In this context, Hycleus, the most speciose genus of the beetle family Meloidae, with at least 430 species, represents an interesting model to explore the phylogeny of a mega-diverse taxon. The systematic of this genus has never been investigated, but its members were divided into three “sections” according to the mesosternal morphology, whereas some lineages have been detected according to additional morphological characters. Previous molecular studies pointed out the close relation among Hycleus and both genera Ceroctis (59 species) and Paractenodia (5 species), forming a complex of ca 500 species. In the attempt to study the phylogenetic relationships among the species of this mega-diverse taxon, we tested about one hundred species (92 Hycleus, 16 Ceroctis and 3 Paractenodia) with both mitochondrial (COI) and nuclear (CAD, 28S, ARGK, Wingless) markers. Our Maximum Likelihood and Bayesianbased results showed that the three Hycleus “sections” are polyphyletic and lack of a taxonomic value, whereas some of the groups morphologically described were confirmed and well supported. Furthermore, the monophyly of the complex Hycleus-Ceroctis-Paractenodia was verified, suggesting that a new taxonomic arrangement of these taxa is required. However, in most cases, the basal nodes of the trees remained unsolved, therefore, to better define the deepest phylogenetic relationships, the application of novel markers is required.