Built to keep out marauding tribes, the Great Wall of China, completed during the Ming dynasty (A.D. 1368-1644), has affected the course of plant as well as human history.
Great divider.
CREDIT: (TOP) HONGYA GU
"The Great Wall has served as a physical barrier to gene flow between [floral] subpopulations separated for more than 600 years," according to plant geneticist Hongya Gu of Beijing University. Gu and colleagues studied one population from each of the four species of insect-pollinated plants and two species of wind-pollinated plants that grow on both sides of the Great Wall. They report in the March issue of Heredity that, compared with control plants from two sides of a road, there was "significant genetic differentiation" between plants and their counterparts on the other side of the 2400-kilometer wall, whose height ranges up to 7.1 meters. Wind-pollinated species showed less differentiation than insect-pollinated species. "This is a fine example [of] how easy it is for populations to diverge," especially because of the absolute dating, says Peter Raven, director of the Missouri Botanical Garden.
