Three-spine sticklebacks aren't as pretty as many aquarium fish, and anglers don't fantasize about hooking one. But biologists treasure these small fish for what they are revealing about the genetic changes that drive evolution. Now, researchers have sequenced the stickleback genome for the first time, and they have discovered that as fish in different parts of the world adapted to live in fresh water, the same sites in the genome were changed time and again.
Their findings, published April 5, 2012, in the journal Nature, indicate that changes to both genes and, more commonly, stretches of DNA that control gene activity, have driven sticklebacks' adaptation to fresh water environments.
"The cool thing about these fish is that they've colonized a whole series of new environments in the last 10,000 to 20,000 years," says Howard Hughes Medical Institute (HHMI) investigator David Kingsley of Stanford University School of Medicine. As the glaciers melted at the end of the last ice age, marine sticklebacks ventured into fresh water, settling in rivers, lakes, and streams. The fish adapted to their new homes. Compared with their marine relatives, freshwater sticklebacks tend to be smaller and sleeker, with less bony body armor. The challenges of surviving in new habitats also prompted modifications to their teeth, jaws, kidneys, coloration, and numerous other traits. Moreover, this pattern of colonization and adaptation has repeated itself in several areas where sticklebacks live, including the east and west coasts of North America, western Europe, and eastern Asia. "A world-wide collection of lakes and streams became countless natural evolutionary experiments," says Kingsley.
These evolutionary experiments afford researchers the opportunity to uncover the genetic changes responsible for particular adaptations. In previous studies, Kingsley and colleagues have teased out three examples. In 2005, for instance, the researchers repor
|Contact: Jim Keeley|
Howard Hughes Medical Institute