Molecular and morphological evidence reveals hybridisation between two endemic cyprinid fishes

Abstract

The geographic occurrence of moggel Labeo umbratus × mud fish Labeo capensis hybrids and the threat of hybridisation to the genetic integrity of L. umbratus were investigated. Genetic evidence from mtDNA cytb and nDNA s7 intron sequence data indicated probable interspecific hybridisation in two impoundments, Hardap Dam (Orange River Basin, Namibia) and Darlington Dam (Sundays River Basin, Eastern Cape, South Africa). Some putative hybrids were morphologically identifiable on account of their meristic and morphometric intermediacy to the parent species.Human activities appear to drive the observed hybridisation, either through dam construction and direct stocking of L. umbratus or via translocation of Labeo capensis and the previously isolated Orange River lineage of L. umbratus into the southern-flowing systems by inter-basin water transfers. It is recommended that further translocation of fish from these areas should be avoided.

South Africa’s Pathways of Introduction and Dispersal and How They Have Changed Over Time

“…For example, the Orange-Fish-Sundays inter-basin water transfer scheme (figure below), which was completed in 1978, has resulted in the dispersal of Orange River fishes, including Labeobarbus aeneus (Smallmouth Yellowfish), Clarias gariepinus (African Sharptooth Catfish) and Labeo capensis (Orange River Mudfish), into the Great Fish and Sundays Rivers. Known impacts of these introductions include competition with and predation on native biota (Ellender and Weyl 2014;Weyl et al 2016) and hybridisation between the Orange River Labeo and Eastern Cape populations of the closely related Moggel L. umbratus (Ramoejane et al 2019).…”

“…12.4 Medicago polymorpha (Bur Clover) could have been introduced to South Africa as early as around 760 AD, possibly entangled in the wool of sheep brought into the country from elsewhere in Africa(Deacon 1986) (photograph courtesy of J.M. Kalwij) Box 12.2 (continued)The Orange-Great Fish-Sundays River inter-basin water transfer scheme resulted in the extralimital introduction of Labeo capensis (Orange River Mudfish), Labeobarbus aeneus (Smallmouth Yellowfish), Clarias gariepinus (African Sharptooth Catfish) and Austroglanis sclateri (Rock Catfish) into the Great Fish and Sundays Rivers (redrawn fromRamoejane et al 2019) 12.2.2.2 Colonial Period (1650-1910…”

Identification and characterization of hybrids of Acipenser ruthenus and Acipenser baerii (Actinopterygii, Acipenseriformes) from the Irtysh River

“…This also applies to sturgeons (Lagunova 1999;Ludwig et al 2009;Dudu et al 2011). On the one hand, hybridization contributes to the extinction of many species in direct and indirect ways (Borkin and Litvinchuk 2013;Chafin et al 2019;Ramoejane et al 2019); on the other hand, natural hybridization plays an important role in the evolution of many plant and animal taxa (Allendorf et al 2001;Mallet 2007;Schwenk et al 2008). In fish, natural hybridization is quite common (Allendorf et al;2001).…”

Distribution of host-specific parasites in hybrids of phylogenetically related fish: the effects of genotype frequency and maternal ancestry?

“…Such hybridization very often results from the introduction or invasion of non-native fish species [12][13][14][15][16] caused by direct anthropogenic activities (agriculture, fish farming and waterbodies transformation) or human-mediated disturbances of nature (climate change, interspecies competition or limited living resources). Generally, the presence of F1 hybrids is documented in many wild-living cyprinids even when the frequency of hybrids is rather low [6,[16][17][18][19][20][21][22]. Cyprinid hybrids exhibit high larval resistance to environmental disturbances (osmotic and thermal conditions), wider ecological plasticity, greater fasting abilities in comparison to their parents, and limited susceptibility to parasite infection [7,[23][24][25].…”