Nine in one: integrative taxonomic evidence of hidden species diversity in the widespread Zambezi grunter, Parauchenoglanis ngamensis (Siluriformes: Auchenoglanididae), from southern and south-central Africa

The Zambezi grunter, Parauchenoglanis ngamensis, is currently distributed across four (sub)basins in southern and south-central Africa, namely the Okavango, upper Zambezi, Kwanza, and Kasai. The present study used a combination of molecular (barcoding), colour pattern, and other morphological data to explore the possible existence of hidden species diversity within this species. Based on the available samples, analyses of molecular data uncovered seven well-supported (.96–1.00 Bayesian posterior probabilities) candidate species, with 1.6%−8.5% genetic divergence between them. These, in addition to two more candidate species without genetic data, exhibited a combination of consistent colour pattern and other morphological differences that supported their distinction. The present study redescribes P. ngamensis, which is confined to the Okavango and upper Zambezi (sub)basins, and describes eight new species: two from the Kwanza Basin and six from the Kasai sub-basin. The fact that some of the species occur allopatrically, whereas others are sympatric and even syntopic indicates the complex palaeogeographical history of these basins. In addition, the high species diversity discovered in the Kasai sub-basin seems to be related to its highly peculiar hydrography. Accurate delimitation of species boundaries and mapping of their distribution is crucial for conservation assessments and guiding their protection.