Speciation rates in lakes and the enigma of Lake Victoria

Rates of evolutionary change in Lake Victoria continue to stimulate debate. If, as some have claimed, the present fauna is <15000 years old, speciation must have proceeded apace and, more significantly, morphological and ecological differentiation, especially among the several hundred endemic haplochromine cichlid fishes, has been remarkable. Attempts to demonstrate that similar situations are not unusual in young lakes are frustrated by the facts. Some alleged examples of rapid speciation are undoubtedly incorrect, others are questionable, and the striking morphological changes, so abundantly demonstrated, especially by the haplochromines, cannot be matched elsewhere. The complexities of the evolutionary and distributional histories of the animals concerned have often neither been appreciated nor considered by those who postulate a recent desiccation of L. Victoria. If Greenwood's superflock concept is correct, haplochromine genera that supposedly evolved so recently in L. Victoria have representatives in L. Kivu that must have been there since well before this alleged but unproven event. Reference is made to new discoveries that have a bearing on the origin and history of the superflock, but which suggest different explanations. As a prelude to the biological aspects of the matter, recent geophysical and palaeolimnological investigations are considered, and many uncertainties and contradictions are revealed.