Fat lips evolve at record speed 18:18 14 May 2010 by Andy Coghlan For similar stories, visit the Evolution Topic Guide Fish in a remote crater lake in Nicaragua are splitting into separate species at breakneck speed.
It has taken the lake cichlids just 100 generations and as many years to evolve an entirely new physical feature: very fat lips. Most estimates of how fast species evolve new features are based on models, which generally indicate that it could take up to 10,000 generations. Some models suggest just tens of generations are enough, but such rapid change has never been documented before. Axel Meyer at the University of Konstanz in Germany and his team say the fat-lipped fish occupy a different ecological niche from their thin-lipped cousins, despite living in the same lake, which fills a volcanic crater formed 1800 years ago. They don't eat the same diet and observations of captive fish in a tank suggest they avoid mating with each other though lab experiments show they can still interbreed. Meyer says the fact that if they avoid mating with each other in the wild, as seems likely, they are well on the way to becoming separate species. The new variety have narrower, pointy heads, ideal for nibbling insects and larvae from crevices in the volcanic rock, and fat lips to cushion their ventures into the sharp crags. The thin-lipped variety have sturdier jaws and extra teeth to crack the shells of the snails they feed on. "When scientists catch incipient species in the process of divergence, it is important, because it is difficult to catch the process in action," says Todd Streelman of the Georgia Institute of Technology in Atlanta, who also studies cichlid evolution. "This new work nicely matches theories developed in the 1990s suggesting that species could develop rapidly even when they share the same environment." Journal reference: BMC Biology, vol 8, p 60
