A new species of Potamonautes from São Tomé Island, Central Africa, with redescriptions of P. margaritarius (A. Milne-Edwards, 1869) from São Tomé, and P. principe Cumberlidge, Clark and Baillie, 2002, from Príncipe (Decapoda: Potamonautidae)

Abstract

Surveys of the freshwater crabs of two islands in the Gulf of Guinea, Central Africa, allowed a revision of the taxonomy of two little-known island endemic species, based for the first time on adult males: Potamonautes margaritarius (A. Milne-Edwards, 1869) from São Tomé, and of P. principe Cumberlidge, Clark and Baillie, 2002, from Príncipe (Brachyura; Potamonautidae). A new species of Potamonautes from southern São Tomé (Potamonautes saotome sp. nov.) is also described that is genetically distinct and has a clearly separate geographic distribution from P. margaritarius from northern São Tomé. The new species from southern São Tomé can be recognized by a suite of characters of the carapace, thoracic sternum, and gonopods. The taxonomy of P. margaritarius (A. Milne-Edwards, 1869) is stabilized by selecting a neotype from northern São Tomé. Potamonautes principe from Príncipe is the most distinct of the three taxa, with a more swollen carapace that has smooth anterolateral margins, and a shorter, straighter male first gonopod. All three taxa are morphologically distinct species that have also been clearly distinguished as evolutionarily separate lineages by mtDNA analysis and haplotyping in an earlier study. Previous phylogenetic evidence supports two separate island colonization events at different times in the past from different ancestral populations, one to São Tomé and another to Príncipe that resulted in the establishment of the endemic freshwater crab faunas of these two islands.