Show me your colour: the neuroendocrine and molecular underpinnings of phenotypic variation in colour and aggression in cichlid fish

One of the most intriguing questions in evolutionary biology is why some groups of animals contain many species while others contain only a few. One important factor influencing biodiversity is selection on a male secondary sexual trait arising from aggressive competition between males to gain access to females or resources. Colour polymorphic species are excellent to study effects of competition on the evolution of phenotypic diversity.