Multigene analysis reveals that Pseudopalaemon Sollaud, 1911 is a junior synonym of the widespread genus Macrobrachium Spence Bate, 1868 (Decapoda: Caridea: Palaemonidae)

Pseudopalaemon Sollaud, 1911 is a species-poor genus of freshwater palaemonid shrimps endemic to South America, especially the Amazon Basin. Morphologically, the differentiation between Pseudopalaemon and Macrobrachium Spence Bate, 1868 is based solely on the presence or absence of a mandibular palp. Previous phylogenetic studies, based on inclusion of a single species, have nevertheless questioned the reliability of this character as the sole taxonomic criterion for differentiating these two genera. Herein we provide genetic data for three out of a total of seven species, currently included in the genus, including its type species. The results clearly demonstrate that Pseudopalaemon is fully nested within Macrobrachium and furthermore does not constitute a monophyletic group. Therefore, Pseudopalaemon is herein considered to be a junior synonym of Macrobrachium.