Phylogenetic relationships among the species of the Cameroonian endemic freshwater crab genus Louisea Cumberlidge, 1994 (Crustacea, Brachyura, Potamonautidae), with notes on intraspecific morphological variation within two threatened species.

Louisea Cumberlidge, 1994 (Crustacea, Brachyura, Potamonautidae) currently includes four endemic Cameroonian freshwater crab species whose phylogenetic relationships were previously unresolved. In the present study, phylogenetic analyses are carried out involving three mtDNA loci (COI, 12S rRNA, and 16S rRNA). The COI locus revealed divergence times of 5.6 million years ago (myr) for when L.balssi (Bott, 1959) diverged from L.edeaensis (Bott, 1969); 4.1 myr for when L.edeaensis diverged from L.yabassi Mvogo Ndongo, von Rintelen & Cumberlidge, 2019; and 2.48 myr for when the later species diverged from L.nkongsamba Mvogo Ndongo, von Rintelen & Cumberlidge, 2019. Three genetic lineages were found within L.nkongsamba that are supported by uncorrected p-distances and the haplotype network. Morphological variation in some taxonomically important characters was found within both L.nkongsamba and L.yabassi. No correlation, however, was found between the morphotypes within these species and the uncovered genetic lineages. Recognition of species boundaries and of subpopulations of species will prove valuable when making informed conservation decisions as part of the development of species action plans for these rare and threatened freshwater crabs.