ScienceDaily (May 11, 2006) — Plant and animal breeders have long used hybridization to transfer useful traits between species. But does the same process happen without human aid? In a new study in the June issue of American Naturalist, Kenneth D. Whitney (Indiana University and Rice University), Rebecca A. Randell (Indiana University), and Loren H. Rieseberg (Indiana University), explore how spontaneous hybridization -- known as adaptive trait introgression -- has a vital impact on adaptation and evolutionary diversification.

"The role of hybridization in adaptive evolution is contentious. While many cases of adaptive trait introgression have been proposed, the relevant traits have rarely been identified, resulting in a lack of clear examples of this process," write the authors.

The researchers examined a northern sunflower species that had captured genes from a southern sunflower species, resulting in a stabilized hybrid, Helianthus annuus texanus, able to expand southward into central and southern Texas. They then recreated the original hybridization event by manually crossing two parent species. Not only were these hybrids resistant to the insects that attack sunflowers, they also produced more seeds than the uncrossed plants.

"The results show for the first time that adaptive trait introgression can be a potent evolutionary force, broadening our view of the mechanisms by which populations adapt to their environments," explain the authors.

Founded in 1867, The American Naturalist is one of the world's most renowned, peer-reviewed publications in ecology, evolution, and population and integrative biology research. AN emphasizes sophisticated methodologies and innovative theoretical syntheses--all in an effort to advance the knowledge of organic evolution and other broad biological principles.

Reference: Kenneth D. Whitney, Rebecca A. Randell, and Loren H. Rieseberg. "Adaptive introgression of herbivore resistance to traits in the weedy sunflower Helianthus," The American Naturalist 167:6.

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