Introduction
The cichlid family of fishes is one of the most species-rich of all vertebrate families. Most of these species occur in three East African lakes, Lake Victoria, Lake Tanganyika and Lake Malawi. Lake Malawi is a rift lake with a maximum depth of 785 meters that is permanently stratified below 250 meters (Love-McConnell 1993). Lake Malawi is inhabited by 9 different families of fishes (Love-McConnell 1993), but the dominant family is Cichlidae. At least 500 endemic species of cichlid fishes are recognized in Lake Malawi (Barlow 2000). The Lake Malawi basin is 4.5-8.6 million years old (Martens 1997). The cichlids are thought to have invaded Lake Malawi from a monophyletic origin (Meyer 1993). These features have made the cichlids one of the favourite model systems for adaptive radiation. Adaptive radiation can be defined as the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage (Schluter 2000). In this paper I will try to discuss the main processes that have lead to the extraordinary species richness shown by the Lake Malawi cichlids.
Colour differences between closely related
Aulonocara..........photo: Fredrik Hagblom
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