Evidence of hidden diversity and taxonomic conflicts in five stream fishes from the Eastern Zimbabwe Highlands freshwater ecoregion

Abstract

Stream fishes of the Eastern Afromontane region are among the least studied vertebrates in this region, despite the potential for harbouring cryptic diversity. The present study examined mitochondrial cytochrome oxidase subunit I (COI) sequence divergence in 153 specimens of stream fishes belonging to four genera and three families, [(Amphilius and Zaireichthys (Amphiliidae); Chiloglanis (Mochokidae); and Hippopotamyrus (Mormyridae)], in the Eastern Zimbabwe Highlands (EZH) freshwater ecoregion to explore the extent to which the current taxonomy conceals the ichthyofaunal diversity in the region. The General Mixed Yule Coalescent (GMYC) species delineation method identified 14 clusters within five currently recognised 'species' from the EZH ecoregion. Only one of these clusters represents a named species, while 13 of them represent candidate or undescribed species. Our results revealed that effective conservation of this region's unique biota is limited by the incomplete knowledge of taxonomic diversity and inaccurate mapping of species distribution ranges.

Deep genetic and morphological divergence in the Hippopotamyrus ansorgii species complex (Teleostei: Mormyridae) in southern Africa

“…Findings from the present study support a growing body of literature which shows that many of the species that were previously considered to have broad geographic ranges across multiple isolated river systems in southern Africa are complexes comprising several historically isolated lineages, with some of them representing novel species (Chakona et al, 2018;Eccles et al, 2011;Kramer et al, 2012;Maake et al, 2014;Riddin et al, 2016). There are at least seven lineages within the H. ansorgii complex that need to be formally described following generation of additional data and detailed examination of a comprehensive number of voucher specimens.…”

“…longilateralis Kramer &Swartz, 2010, were described from the Upper Zambezi and Kunene rivers, respectively, with additional lineages still awaiting the determination of their taxonomic status (Kramer et al, 2004;Kramer & Swartz, 2010). A recent study that focused on populations from the eastern Zimbabwe highlands freshwater ecoregion uncovered existence of additional genetically divergent lineages within the slender stonebasher, highlighting that H. ansorgii as currently described conceals mormyrid diversity in southern Africa (Chakona et al, 2018).…”

“…This area encompasses the Angolan Highlands, which are drained by three major river systems, including the Kwanza, Kunene and Okavango rivers. H. ansorgii has been recorded from several river systems in southern Africa that include the Kwanza, Kunene, Okavango, Kwando, Upper Zambezi, Lower Zambezi, Pungwe and Buzi rivers (Bell-Cross & Minshull, 1988;Kadye et al, 2008;Marshall, 2010;Skelton, 2001;Chakona et al, 2018; Figure 1). Nonetheless, there are no records of this species from the middle Zambezi River, which forms a geographic divide between the western (Kwanza, Kunene, Okavango, Kwando and Upper Zambezi Rivers) and the eastern (Ruo, Pungwe and Buzi rivers) populations (Figure 1).…”

Integrative taxonomy reveals hidden diversity in the southern African darters genus Nannocharax Günther 1867 (Characiformes: Distichodontidae)

“…In contrast, for the bPTP approach, these limits are defined by the number of nucleotide substitutions between haplotypes, not requiring an ultrametric tree. Both approaches have been widely applied in a number of studies to reveal hidden diversity within morphologically defined species and also for delimitation of candidate species in taxonomic groups that have been poorly studied morphologically ( e.g ., Chakona et al ., 2018; Crivellaro et al ., 2017; Kordbacheh et al ., 2017; Ottoni et al ., 2019). Following both methods, the original Nannocharax data set consisting of 35 sequences was reduced to include only unique haplotypes, resulting in 29 sequences.…”

Journal of Fish Biology special issue on The Biology and Ecology of African Freshwater Fishes

“…This adds to the growing evidence for the existence of high level of undocumented diversity in freshwater fishes of southern Africa ( e.g . Chakona et al, 2013, 2018). Whereas S. capensis sensu lato has a broad geographic range, the newly identified lineages within this species complex have more restricted distributions (Bronaugh et al, 2020), and are also likely to have smaller population sizes, making them more susceptible to extinction from multiple anthropogenic impacts such as alien fish predators, water extraction and the projected climate change (Ellender et al, 2017; Shelton et al, 2018).…”