Abstract
Sampling of remote inland aquatic habitats in South Africa has constantly been yielding novel endemic freshwater crab species (Potamonautes MacLeay,1838). During the present study, we report on the discovery and description of two new freshwater crab species (Potamonautes baziya sp. nov., and P. mariepskoppie sp. nov.) from Afrotemperate forested mountain regions in the Eastern Cape and Mpumalanga provinces of South Africa, respectively. Phylogenetic evidence derived from DNA sequence data of three partial mitochondrial loci (12S rRNA, 16S rRNA and cytochrome oxidase subunit one, COI) corroborates the evolutionary distinction of the two novel species. In addition, morphological and ecological data for the two new species further delineate their evolutionary distinction from congeneric sister species. A comparison of the taxonomically important gonopods 1 and 2 and carapace features among the sister species and other known freshwater crabs of South Africa was further used to provide evidence for the distinction of the two novel species. The discovery of two new species suggest that remote mountainous areas or unsampled regions in South Africa likely harbor several novel species, reiterating a call to document aquatic inland biodiversity in forested and mountainous regions of the country.
Highlights
The alpha taxonomy of South African freshwater crabs (Potamonautes MacLeay, 1838) is well-established and an exemplar of one of the best studied inland aquatic crustacean groups in the Afrotropical region (Daniels 2017; Daniels et al 2012, 2019; Peer et al 2015, 2017; Phiri & Daniels 2014, 2016)
The ML and BI phylogenetic analyses based on the 1278 nucleotides of the three combined mtDNA loci, comprising 600 bp, 316 bp and 362 bp fragments for cytochrome oxidase subunit one (COI), 12S rRNA and 16S rRNA, respectively, retrieved a monophyletic and statistically well-supported Potamonautes MacLeay, 1838 (Fig. 1)
The southern African mountain stream species comprised one clade, with P. baziya sp. nov., from the Baziya forest station in the Eastern Cape as sister to two Drakensberg Mountain endemic species, P. clarus Gouws, Stewart & Coke, 2000 and P. depressus Krauss,1843. The latter clade was in turn sister to species from the Cape Folds Mountain (CFM), with P. sp. nov. from Hogback as sister to P. parvispina Stewart, 1997, and this clade was sister to P. parvicorpus Daniels, Stewart & Burmeister, 2001 sister to P. brincki Bott, 1960 sister to P. tuerkayi Wood & Daniels, 2016
Summary
The alpha taxonomy of South African freshwater crabs (Potamonautes MacLeay, 1838) is well-established and an exemplar of one of the best studied inland aquatic crustacean groups in the Afrotropical region (Daniels 2017; Daniels et al 2012, 2019; Peer et al 2015, 2017; Phiri & Daniels 2014, 2016). The discovery of new freshwater crab species was largely galvanized by the application of molecular tools such as allozyme electrophoresis and more recently DNA sequencing (Daniels 2017; Daniels et al 2014, 2019, 2020b; Gouws et al 2000, 2001; Peer et al 2015, 2017; Phiri & Daniels 2014, 2016). The continued discovery of new freshwater crab species can be attributed to the fact that large areas of the country remain unsampled. These areas should be the focus of future systematic surveys, in areas or biomes where habitats are naturally fragmented, creating an ideal template for allopatric speciation
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