Taxonomic review of Perisesarma (Decapoda: Brachyura: Sesarmidae) and closely related genera based on morphology and molecular phylogenetics: new classification, two new genera and the questionable phylogenetic value of the epibranchial tooth

摘要

The crab genus Perisesarma De Man, 1895 has been shown to be a polyphyletic taxon comprising morphologically heterogeneous species. Some members of the genus have a close phylogenetic relationship with the sister genus Parasesarma De Man, 1895, with which it shares many morphological similarities, except for the existence of an epibranchial tooth in Perisesarma. This study uses morphological and molecular approaches to reconstruct phylogenetic relationships of Perisesarma and related genera and to evaluate the phylogenetic importance and taxonomic usefulness of the epibranchial tooth. As genetic markers we use two mitochondrial and one nuclear gene. A comparative morphological analysis reveals that a clean separation between species of Parasesarma and Perisesarma is not possible, because of intermediate conformations of the epibranchial tooth. In our molecular analysis, most species of Perisesarma cluster solidly together with species of Parasesarma, but without being reciprocally monophyletic. Morphology and genetics also indicate that the West African species of Perisesarma and the Indo-Pacific P. fasciatum are markedly different from all other species of the genus. Therefore, we here suggest with robust double support a new classification, transferring most species of Perisesarma to Parasesarma and the three West African representatives and P. fasciatum into new genera, thereby restricting the genus Perisesarma to the type species P. dusumieri.