Ontogenetic and evolutionary change of external morphology of the neotropical shrimp Potimirim (Holthuis, 1954) explained by a molecular phylogeny of the genus

Abstract

A phylogenetic analysis of a fragment of the mitochondrial gene 16S was used to test the monophyletic status of Potimirim. Existing doubts on the taxonomic status of Potimirim brasiliana (once P. glabra) and P. potimirim (once P. mexicana) were clarified. Potimirim mexicana and P. potimirim are distinct species according to molecular data and appendix masculina morphology. A new species (Potimirim sp. 1) from Puerto Rico was revealed with molecular data, and it is evolutionarily related to P. potimirim and P. mexicana according to our analysis. We found out three distinct species under the name P. glabra. Then, we recommend the application of the name P. glabra for the populations of the Pacific slope of Central America and revalidation of P. brasiliana for the Brazilian ones. The need for a new name to those “P. glabra” of the Caribbean is highlighted, and it was provisionally referred as Potimirim sp. 2. The ontogenetic (juveniles to adults) development of the appendix masculina of P. brasiliana was observed and compared to the other species of Potimirim (adults). In the light of our phylogenetic hypothesis, we postulate a pattern of character addition for the evolution of the appendix masculina of Potimirim. This hypothesis is plausible for two key reasons. First, Potimirim is a monophyletic group according to our hypothesis. Second, the shape of appendix masculina found in adults of P. americana is similar and comparable to those found in the earliest juvenile stages of P. brasiliana, a derived species according to our phylogeny (P. americana, ((P. mexicana, Potimirim sp. 1, P. potimirim), (P. glabra, (P. brasiliana, Potimirim sp. 2)))). As so, the basal P. americana retain the ancestral morphological state of the appendix masculina when compared to the other species of Potimirim. In our interpretation the ontogeny of the appendix masculina recapitulated the proposed phylogeny, giving further support to it.