Testing ecological speciation in Lake Tanganyika cichlids

The importance of natural (ecological) selection is increasingly emphasized in studies of speciation. The cichlids of the East African Great Lakes are among the most spectacular examples of rapid speciation and adaptive radiation. Surprisingly, the role of ecological speciation in the evolution of these fish faunas remains largely untested.

The aim of the project is to study genetic population structure, ecological and mating preferences of populations within a candidate model system of ecological speciation. Telmatochromis temporalis is an algal-feeding, highly sedentary, benthic breeding cichlid endemic to Lake Tanganyika. This species is dimorphic in body size and inhabits two different habitats in multiple sections of the lake. The normal form (Standard Length [SL] up to 85 mm, minimum SL at sexual maturity 60 mm) occurs along the shallow rocky shores and breeds in rock crevices whereas the dwarf form (SL up to 44 mm, minimum SL at sexual maturity 38 mm) inhabits and breeds within shell beds formed by accumulation of empty gastropod shells. Hence, the two forms of Telmatochromis temporalis show marked ecotypic variation. This strongly suggests potential for ecological speciation by disruptive natural selection on breeding habitat preferences.

Objectives:

• To test between two alternative hypotheses for the occurrence of dwarf and normal forms in Telmatochromis temporalis: (A) parallel ecological speciation or (B) occurrence of largely panmictic ecomorphs using amplified fragment length polymorphisms (AFLPs).
• To test for behavioural and ecological preferences of the two forms under experimental aquarium conditions
• To test whether the two forms mate assortatively using controlled mate choice trials.
• To determine whether differences in body size and size at sexual maturity have a genetic basis and are not primarily determined by environmental plasticity, using controlled common garden rearing experiments on first generation offspring.

Outcomes for the student

This studentship will be an excellent period of training in molecular ecology and behavioural ecology methodologies, benefiting from the support of active research groups within the Department of Zoology, NHM and the School of Biological Sciences, Bristol. The student will receive training in state-of-the-art molecular DNA techniques and population genetic analyses. In addition, there will also be opportunities for fieldwork in Zambia and Tanzania. The student will receive training to communication results to both scientific and public audiences.

Supervisors

Dr Lukas Rüber (Department of Zoology, NHM; l.ruber@nhm.ac.uk) and Dr Martin J. Genner (University of Bristol; M.Genner@bristol.ac.uk).