Pseudotropheus demasoni from Lake Malawi. Photo by Dave Hansen
A new study may may shed some light on the incredible diversity of cichlids in Lake Malawi. The question of how over 1000 species evolved in a single lake may have been answered by core samples obtained through the Lake Malawi Drilling Project. Core samples from the last 1.3 million years of the lake's history show drastic changes in water levers, pH and salinity.
Dry periods in Lake Malawi's history have dropped waters levels over 200 meters a couple dozen times. During the low level periods, habitats changed as the water receded and fish became isolated into smaller lakes. As wetter periods returned and lake level's rose, once isolated species once again were joined. All of these extreme changes led to fish who are also able to change in order to survive. The full, unrestricted article titled "Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity" can be found on the National Academies of Science website.