How many species of cichlid fishes are there in African lakes?

Abstract

The endemic cichlid fishes of Lakes Malawi, Tanganyika and Victoria are textbook examples of explosive speciation and adaptive radiation, and their study promises to yield important insights into these processes. Accurate estimates of species richness of lineages in these lakes, and elsewhere, will be a necessary prerequisite for a thorough comparative analysis of the intrinsic and extrinsic factors influencing rates of diversification. This review presents recent findings on the discoveries of new species and species flocks and critically appraises the relevant evidence on species richness from recent studies of polymorphism and assortative mating, generally using behavioural and molecular methods. Within the haplochromines, the most species-rich lineage, there are few reported cases of postzygotic isolation, and these are generally among allopatric taxa that are likely to have diverged a relatively long time in the past. However, many taxa, including many which occur sympatrically and do not interbreed in nature, produce viable, fertile hybrids. Prezygotic barriers are more important, and persist in laboratory conditions in which environmental factors have been controlled, indicating the primary importance of direct mate preferences. Studies to date indicate that estimates of alpha (within-site) diversity appear to be robust. Although within-species colour polymorphisms are common, these have been taken into account in previous estimates of species richness. However, overall estimates of species richness in Lakes Malawi and Victoria are heavily dependent on the assignation of species status to allopatric populations differing in male colour. Appropriate methods for testing the specific status of allopatric cichlid taxa are reviewed and preliminary results presented.

Disruptive sexual selection on male nuptial coloration in an experimental hybrid population of cichlid fish

“…A 'partial partitioning' design (Hert 1989;Turner et al 2001) was used, allowing for full interaction between males and females and spawning. Compartments were separated by plastic grids with adjustable mesh size, allowing the females, but not the larger males, to pass through the grid.…”

A test of the utility of DNA barcoding in the radiation of the freshwater stingray genus Potamotrygon (Potamotrygonidae, Myliobatiformes)

“…Radiations are not rare or restricted in time or space, and usually fill a previously unoccupied niche. Some examples include the Cambrian radiation (Philippe et al, 1994;Bromham et al, 1998;Conway-Morris, 1999), Anolis lizards from the Caribbean (Jackman et al, 1999), Toffoli et al 331 (Baldwin and Sanderson, 1998), cichlid fishes of the east African lakes (Avise, 1990;Turner et al, 2001), and sciaenid fishes of the western Atlantic (Vinson et al, 2004), among others.…”

Morphological variations of wild populations of Nile tilapia (Oreochromis niloticus) living in extreme environmental conditions in the Kenyan Rift-Valley

“…They exhibit remarkably high levels of genetic and morphological diversity, which affect their morphology, ecology, behaviour and genomes (Nelson 1994;Barlow 2000;Chakrabarty 2005). A large extent of cichlid diversity is observed in three main East African Lakes (Victoria, Tanganyika and Malawi) where 1800 to 2000 species (60 % of all cichlid species worldwide) are present in species flocks (Greenwood 1984;Turner et al 2001). These cichlid species flocks are primarily monophyletic groups of closely related species inhabiting the same ecosystem, and evolved from a single ancestral species (Greenwood 1974).…”