Molecular phylogenetics and taxonomic reanalysis of the family Mithracidae MacLeay (Decapoda : Brachyura : Majoidea)

Abstract

Mithracid crabs comprise a primarily subtidal reef- and rubble-dwelling group inhabiting both tropical and subtropical seas. Despite their relative ubiquity in many hard-substrate environments, there has been little consensus about their phylogenetic relationships or whether their group rank should be that of subfamily or family. We have used a combined molecular dataset of two nuclear (18S, H3) and three mitochondrial (12S, 16S, COI) genes to build a preliminary molecular phylogeny of Majoidea in order to examine the membership of Mithracidae. We then built a second molecular phylogeny based on three mitochondrial genes to assess the internal composition of the family, and conducted comparative morphological examinations of genera and species that resolved in unexpected positions on the phylogram. Four genera are designated under new or resurrected names on the basis of molecular and morphological characters, while memberships of several other existing genera are modified. Following review of molecular and morphological characters, the genera Coelocerus, Cyclocoeloma, Cyphocarcinus, Leptopisa, Micippa, Picrocerodes, Stenocionops and Tiarinia are provisionally excluded from Mithracidae s.s., while Hemus and Pitho are included in it. A key to genera of Mithracidae is provided.