Evidence of paraphyly in the neotropical Porcellanid genus Neopisosoma (Crustacea : Anomura : Porcellanidae) based on molecular characters

Molecular data were used to evaluate the validity of the genus Neopisosoma Haig, 1960. Comparisons of morphological features within Neopisosoma sugges t the existence of two lineages, represented among others, by N. angustifro ns (Benedict, 1901) and N. neglectum Werding (1986). Both lineages of Neopi sosoma are more similar to two morphologically different species groups of the genus Pachycheles, than to congeners of the other group. Comparative mo rphology of larvae from N. angustifrons, N. neglectum and species of Pachyc heles shows that N. angustifrons closely resembles Pachycheles species, whi lst N. neglectum is set apart. Sequences of a 465 bp segment of the mitocho ndrial gene cytochrome oxidase I (COI) were obtained and used to infer phyl ogenetic relationships among N. angustifrons, N. neglectum, one species of Pachycheles and seven other species of porcellanids, representing three oth er genera. Results of the molecular analysis were congruent to results of c omparative morphological studies of larvae: N. angustifrons grouped with th e Pachycheles species, whereas N. neglectum is placed apart. This led us to the conclusion that the genus Neopisosoma is probably paraphyletic and tha t the criterion used by Haig (1960) is not reliable to define the genus. A revision on a world-wide basis of the genera included, and additional seque nce information will be necessary to satisfactorily resolve relationships w ithin the Porcellanidae.