Hiding in the hills: evidence for two novel mountain-dwelling freshwater crabs of Potamonautes (Decapoda: Brachyura: Potamonautidae) from South Africa

Abstract

Specimens of freshwater crabs (PotamonautesMacLeay, 1838) collected from mountainous regions in the Limpopo and Mpumalanga provinces of South Africa could not be assigned to species level and possibly represented novel lineages. The phylogenetic placement of these two potential novel lineages were investigated with the use of DNA sequence data from three mitochondrial loci (cytochrome oxidase c subunit one - COI, 12S rRNA, and 16S rRNA) and one nuclear locus (histone 3 (H3)), using a maximum likelihood and Bayesian Inference approach incorporating all Potamonautes species described from southern Africa. In addition, a divergence time estimation was undertaken on the tree topology to determine the timing of cladogenesis. Morphometric analyses were also conducted on the two undescribed lineages and co-distributed, phylogenetically closely-related species (P. flavusjoDaniels, Phiri & Bayliss, 2014 and P. mariepskoppieDaniels, Barnes, Marais & Gouws, 2021) using discriminant function analyses of carapace and pereiopod variables. Phylogenetic results revealed that the two novel species are sister groups and related to a clade of endemic subtropical species present in north-eastern South Africa, while the divergence time estimation indicates Mio/Pliocene cladogenesis. The morphometric results corroborate the phylogenetic distinction between the two novel lineages and co-distributed sister species. Potamonautes wolkbergin. sp. and P. aurantiusn. sp. are described and compared with other congeneric South African taxa.