In what could explain earlier findings that just a small number of genetic changes control the widespread evolution of many species of sticklebacks, researchers report in the March 25, 2005,
David Kingsley of Stanford Medical School and the Howard Hughes Medical Institute and colleagues found that reductions in the armor of threespine sticklebacks that have migrated from marine water to freshwater is an example of parallel evolution derived from an allele on a single gene,
"This finding shows that while the morphological change is large, the underlying genetics are simple," Kingsley told
Sequence amplification from 25 random nuclear genes failed to show evidence for one single origin of low-plated sticklebacks. To confirm that different levels of
"This is one of the first times to show the actual gene involved in a major evolutionary change," said Catherine Peichel, of the Fred Hutchinson Cancer Center in Seattle, who was not involved in the study but once worked in Kingsley's lab. It is a good example of selective polymorphism, which is hidden in the marine population, she said: "As soon as the fish go into fresh water, there is strong selection for the allele."
In addition to identifying the gene responsible for the change in stickleback plate armor, this study makes another important point about parallel evolution. "Rather than using hundreds of ways to solve a problem, evolution uses a particular mechanism repeatedly to solve a problem," Kingsley said.
"It would be interesting to know how often this [kind of single gene activity] happens in other plants and animals," said John Postlethwait, of the University of Oregon, who was not involved in the study. While Eda is a gene of major effect, natural selection usually occurs in situations of multiple genes with smaller effects, so it would be interesting to look at this more common situation in natural selection, he said.