LAUSR

Labeo umbratus (Smith, 1841) is a widespread species with populations distributed across isolated southern African river systems. Given that cryptic lineages have been detected in freshwater fishes with a similar distribution, a phylogeographic study of L. umbratus was conducted, considering populations sampled from nine currently isolated river systems between 2008 and 2013. Analyses of mitochondrial DNA (cyt b) and nuclear DNA (S7) sequence data demonstrated that two unique lineages occur in the west-flowing Orange River and south-flowing drainages, respectively. The southern lineage was further divided into three sublineages: one restricted to the Gouritz River, the second largely confined to the Gamtoos River and the last distributed across catchments to the east (the Sundays, Bushmans, Great Fish, Keiskamma, Buffalo and Nahoon rivers). The Great Escarpment and deep incisions along the south coast were identified as potentially influencing the geographic genetic structure of this species. For conservation purposes and pending future taxonomic assessment, the two major lineages were identified as Evolutionarily Significant Units, and Management Units were identified within the southern lineage.