( etic change in each of the 15 freshwate...)Same mutation aided evolution in many fish species, Stanford study finds

Most of these fish evolved independently from marine ancestors that are covered head to hind fin in body armor. Although it's not clear why losing the armor is a benefit to freshwater fish, Kingsley noted that the unarmored fish are lighter and faster than their more burdened marine cousins.

In an effort to learn more about how the armor trait evolves so quickly, Kingsley and his colleagues sequenced that genetic region in a large number of marine fish, all of which had a complete set of armor plates. A small number of these fish had one copy of the Eda gene that contained the mutation in question.

It's likely that when a pocket of sticklebacks got isolated, at least a few of those fish already carried the mutated copy of the Eda gene. When those fish bred, some gave rise to offspring with two copies of the mutation and no (or reduced) body armor. In a freshwater habitat those fish prospered and populated the stream or lake with similarly armorless offspring.

Kingsley said this work is part of a larger study to understand how evolution generates major morphological and physiological changes. "We want to learn how evolution works on a large scale," he said. In previous work, his group found that several species of stickleback lacking hind fins all shared an alteration in how a gene was turned on and off.

The striking similarity is that in both studies evolution turned to the same genetic switch to work a visible change in the fish. However, in the fin study the group wasn't able to pinpoint the exact genetic alteration.

The group continues to wade out into nature, collecting additional stickleback species from around the world that can reveal whe
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Source:Stanford University Medical Center