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A genetic map of the three-spined stickleback
By Birgit Reinert


Researchers have developed a genetic map of the three-spined stickleback, a fish that is studied because it evolves rapidly. They are using the map to trace specific changes in the fish's behavior and physiology to changes in its genome. The map is also a tool for identifying genomic variations among stickleback species and investigating the number of genetic changes required to evolve new traits.

The three-spined stickleback Gasterosteus aculeatus

David M. Kingsley, of the Howard Hughes Medical Institute at Stanford University in California, and colleagues used the map to study changes in skeleton armor and feeding behavior of the three-spined stickleback Gasterosteus aculeatus. Kingsley's team focussed on two stickleback species from British Columbia's Priest Lake—the bentic type found in the grassy shallows of the lake bottom and the limnetic type that inhabits open water. The two species do not interbreed in the wild.

"The fish have evolved so recently that it is still possible to carry out crosses between the new species using artificial fertilization," Kingsley was quoted as saying. "This makes it possible to use genetics to study the number and location of genetic changes that are responsible for evolutionary change."

The researchers discovered that different regions of the genome control the development of different parts of the fish skeleton. "The many different chromosome regions that affect specific aspects of skeletal anatomy in sticklebacks reveal a flexible genetic system for independent modification of the size and number of different feeding and armour structures," the researchers write in Nature.

Comparing the length of the spines, the researchers discovered that the longest spine on the back and another at the bottom are controlled by a single chromosome region. "Having both spine lengths controlled by the same genetic region may help explain how the fish achieve useful modifications," Kingsley said. Three-spined ticklebacks are armed with a row of three heavy spines spaced along the back and a single spine projecting from their belly. The spines are the fish's defense against predators and their length may be crucial for survival.

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Peichel, C.L. et al. The genetic architecture of divergence between threespine stickleback species. Nature 414, 901-905 (December 20, 2001).

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