Systematics of Neotropical freshwater crabs Trichodactylinae based on multi-genes and morphological data: new tribe and new combinations

The generic system of the Neotropical crabs of the subfamily Trichodactylinae H. Milne Edwards, 1853 has remained quite stable over the last 30 years, but the recognition or not of the genus Mikrotrichodactylus Pretzmann, 1968 has been a matter of debate: erected as a subgenus, it was treated with generic status in Rodríguez’ classificatory system but some subsequent works considered it a junior synonym of Trichodactylus Latreille, 1828.

Based on this scenario, an integrative analysis based on molecular (using two mitochondrial, 16 S rRNA and COI, and one nuclear, Histone 3, genes) and morphological (using diagnostic characters traditionally used on the identification of the family) data was performed in order to clarify the phylogenetic position of the genera within Trichodactylinae. The inferred phylogeny recovered three great lineages within Trichodactylinae with high support values in both Bayesian Inference and Maximum Likelihood phylogenetic analyses, corroborated the non-monophyletic status of Trichodactylus, and confirmed the full generic status of Mikrotrichodactylus.

A taxonomic rearrangement of Trichodactylinae is proposed but the positioning of “ Trichodactylus ” quinquedentatus Rathbun, 1893 remains doubtful and was treated herein as a taxon inquirendum et incertae sedis. This taxon seems to be closer related to Rodriguezia Bott, 1969, and Avotrichodactylus Pretzmann, 1968; however, more data are needed before additional taxonomic adjustments concerning its positioning within the subfamily is proposed.

In the current proposal, Trichodactylus is composed by four species, Mikrotrichodactylus by six species, Avotrichodactylus and Rodriguezia by three each, in addition to “ Trichodactylus ” quinquedentatus.