Redescription of Petrolisthes edwardsii (de Saussure) and description of a new, sibling species from the eastern Pacific based on different colour, morphology and genetic identity (Crustacea: Anomura: Porcellanidae)

Petrolisthes edwardsii (de Saussure, 1853) has been viewed as a morphologically variable species with a wide distribution in the tropical and subtropical eastern Pacific. The original description of this species is rather inaccurate, and for more than a century there has been confusion regarding the final repository of type specimens. Material recently collected in the tropical eastern Pacific revealed two different colour morphs, also distinguishable through subtle discrete and continuous differences. Detailed examination of the adult morphology of these two morphotypes and phylogenetic analysis of DNA sequences of a fragment of the mitochondrial COI gene were consistent in the separation of the two forms, irrespective of the geographic origin of the specimens. Therefore, we treat these forms as different species. One form is newly described as Petrolisthes donadio n. sp., the other redescribed as P. edwardsii. The two species live in sympatry across most of their geographic range, and occupy similar habitats. A possible geographical mode of speciation is discussed.