In the lakes of East Africa, fishes of the family Cichlidae have undergone an extraordinarily rapid and extensive radiation. At least 1500 species of cichlid ('sick-lid') fish have evolved from a common ancestor in the last 10 million years. Within Lake Malawi over 700 species have arisen within just the last 2 MY.

Our ultimate goal is to identify mechanisms responsible for speciation of these fishes. What evolutionary forces contribute to speciation? A number of factors are at work, including natural selection on the feeding apparatus, and sexual selection which has produced a riotous variety of male color patterns.

We have spent the last twenty years studying the genetic basis of phenotypic differences among closely related species of the rock-dwelling ‘mbuna’ lineage in Lake Malawi. We have performed QTL studies of the differences in jaw and tooth morphology to understand the genetic basis of trophic specialization. We have also mapped the genetic basis of differences in both male and female color patterns.

We are currently studying the genetic basis of sex determination across the whole family Cichlidae to test the hypothesis that high levels of sexually antagonistic selection lead to higher rates of sex chromosome turnover. For example, we expect that lineages in which only females care for the young (e.g. female mouthbrooding) will switch sex chromosomes systems more frequently that lineages where both parents participate equally in caring for their offspring. Rapid evolution of the gene network controlling gonadal differentiation may lead to hybrid incompatibilities.




Labeotropheus trewavasae


Pseudotropheus tropheopsTropheops.jpg

Melanochromis auratusMelanochromis.jpg
Images by Justin Marshall