The role of the Yala swamp lakes in the conservation of Lake Victoria region haplochromine cichlids: Evidence from genetic and trophic ecology studies

Abstract

Lake Kanyaboli, an isolated satellite lake of Lake Victoria, has been suggested as a potential refugium for haplochromine cichlids that have gone extinct in the main basin of Lake Victoria. Mitochondrial DNA (mtDNA) molecular markers, as well as feeding ecology studies, were employed in this study to re-evaluate the evolutionary and ecological significance of six common Lake Kanyaboli haplochromines. The mtDNA marker revealed high genetic variability within four of the six haplochromine cichlids. Five haplotypes were discerned in Astatoreochromis alluaudi (n = 27), seven in Lipochromis maxillaris (n = 29), five in Astatotilapia nubila (n = 12) and 11 in the endangered Xystichromis phytophagus (n = 205). A haplotype genealogy suggests that Lake Kanyaboli harbours mtDNA haplotypes that could have been lost or not sampled in Lake Victoria, or could have arisen in situ. Lipochromis maxillaris appears to have undergone a recent demographic expansion. The pairwise F ST s indicated that only the comparison between X. phytophagus and A. nubila led to a nonsignificant F ST value. All other comparisons were significant at the 0.01 level, indicating the genetic distinctiveness of the haplochromines in the satellite lake. This could suggest that the lake harbours 'pure' relict populations of the haplochromines and therefore that Lake Kanyaboli can be considered a 'genetic reservoir'. Gut content analysis of the six haplochromine species revealed that eight different food items were consumed. No single species fed exclusively on a single food item, but certain food items contributed higher proportions of the fish diet for each fish species. Resource partitioning therefore could be discerned within this haplochromine community. Thus, Lake Kanyaboli and similar satellite lakes provide an opportunity for conservation of both genetic and trophic diversity threatened by introduction of exotics in the Lake Victoria basin. Lake Kanyaboli should be recognized and conserved as important evolutionary significant units for Lake Victoria region haplochromine species.

Genetic structure and gene flow in an endangered native tilapia fish (Oreochromis esculentus) compared to invasive Nile tilapia (Oreochromis niloticus) in Yala swamp, East Africa

“…Primarily this occurs by isolated habitats with ecological conditions different from Lake Victoria (Chapman et al 2002;Aloo 2003) and that are not yet invaded by aggressive introduced species. Thus, these surrounding small waterbodies act as refugia during the contemporary biodiversity crisis in a manner analogous to their historical role as refugia during the late Pleistocene desiccation of Lake Victoria (Abila et al 2008;Elmer et al 2009;present study).…”

“…Mainly due to anthropogenic influences, particularly the introduction of exotic (Twongo 1995;Balirwa et al 2003). Recent studies on satellite lakes in the Lake Victoria region have lead to the discovery of fish species richness and genetic diversity previously not sampled from Lake Victoria (Chapman et al 2002;Mwanja 2004;Abila et al 2004Abila et al , 2008. This demonstrates that satellite lakes and other small water reservoirs surrounding Lake Victoria are playing a critical role in the evolution and conservation of the region's ichthyofauna in this era of anthropogenically induced extinction.…”

“…Formed through cycles of drying and refilling characteristic of Lake Victoria's geology history (Bishop and Trendall 1966), satellite lakes function as contemporary refugia and therefore have special significance for conservation of Lake Victoria's fauna (Ogutu-Ohwayo 1990;Kaufman and Ochumba 1993;Maithya 1998;Mwanja et al 2001). For example, some recent studies of fishes in satellite Lake Kanyaboli indicated that it may conserve cichlid species richness and genetic diversity that is threatened or extirpated in Lake Victoria proper (Kaufman and Ochumba 1993;Aloo 2003;Abila et al 2008). …”

Interspecific Hybridization of Tilapiines in Lake Victoria, Kenya

“…Satellite lakes like L. Kanyaboli and Namboyo are separated from the main lake by dense papyrus swamps of low dissolved oxygen, and the anoxic conditions restrict the natural invasion of the predatory L. niloticus [31,46]. Similarly, these satellite lakes are less polluted, hence are still dominated by diatoms, which are suitable food materials for indigenous tilapias.…”

Environmental Quality and Fish Communities in Selected Catchments of Lake Victoria

“…From the taste of fish to the quality of drinking water and water for domestic use there are signs that the water quality is an issue of major concern. There is no doubt that it affects the quality of fish, fish abundance and the socio-economic conditions of the riparian communities [32].…”