Morphological identification and molecular data (mtDNA COI) were used to resolve the taxonomic identity of a non-native freshwater shrimp in the Cape Floristic Region (CFR) of South Africa and to evaluate levels of genetic diversity and differentiation in the species' core natural distribution. The species was morphologically and genetically identified as Caridina africana Kingsley, 1882, whose main natural distribution is in the KwaZulu-Natal (KZN) Province, more than 1200 km from the point of new discovery. Subsequently, sequence data from natural populations occurring in seven rivers throughout KZN showed the presence of nuclear copies of the mtDNA COI gene (NUMTs) in 46 out of 140 individuals. Upon removal of sequences containing NUMTs, levels of genetic diversity were low in the alien population (possibly as a consequence of a bottleneck event), while varying levels of genetic diversity and differentiation were found in natural populations, indicating habitat heterogeneity, fragmentation and restricted gene flow between rivers. Following the present study, the alien shrimp has survived the Western Cape's winter and dispersed into a nearby tributary of the Eerste River System, hence posing an additional potential threat to endangered endemics. Understanding the biology of this alien species will aid detection and eradication procedures.
Since the study of Richard and Clark (2009), additional material of Caridina africana Kingsley, 1882 has been examined and as a consequence C. nilotica var. paucipara Weber, 1897 is considered to be a junior synonym of C. africana. Material of Caridina serratirostris De Man, 1892, C. angulata Bouvier, 1905, C. brachydactyla De Man, 1908 and C. moeri Woltereck, 1984 is reported, and redescribed. Caridina serratirostris and C. angulata are reported for the first time from the African mainland, both species being previously known from Madagascar. The first record of C. brachydactyla from the African continent is also noted. Furthermore, Caridina nilotica var. natalensis De Man, 1908 and Caridina nilotica var. brevidactyla J. Roux, 1920 are considered to be junior synonyms of C. brachydactyla. Part of the type series of C. brachydactyla was examined for the present study and this material together with the description and figures of the rostrum illustrated by De Man (1892) as Caridina wyckii appear to be three different species: C. brachydactyla s. str. and probably two new species. These are not described due to lack of additional material available for study. However, two new African species are described and an identification key is provided.
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