Evolution in the fast lane

Adaptation of marine sticklebacks shows that evolution can be rapid

source: Michael Le Page
New Scientist vol 210 no 2806 April 2 2011 starts p 32, 5 pages long

Marine sticklebacks can adapt fast to fresh water conditions, and lose armour plate as part of this adaptation. Michael Bell, biologist from Stony Brook University, New York, has studied sticklebacks from Loberg Lake, Alaska. He found, in two decades to 2007, the fish had evolved the trait of light armour. The fish also developed smaller gills. Similar changes have been seen in Norwegian sticklebacks cut off from marine water. Evolution tends to be slow, according to DNA and fossil evidence, but cases of rapid evolution are more common than previously thought. Studies of sticklebacks elsewhere show that genetic diversity fosters adaptation. 

Rapid evolution may be undetected, because new species may disappear before leaving records. Species may divide then merge back, as has happened in Lake Victoria, Africa. Cichlid species in the lake have begun breeding with one another in response to poor visibility from human activity, which prevents the fish from differentiating between species. Selection is a stronger pressure than thought. Organisms evolve rapidly as environments change, but most evolutionary change is cancelled by further change.