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 FSTs indicated that only the comparison between X. phytophagus and A. nubila led to a non-
significant FST 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.
