A new hybrid species of tumbleweed is living up to the invasive legacy of its forebears as it spreads rapidly throughout California, Science News reports. The tumbleweed, an iconic image of America’s West, is actually made up of several species, all of which came to the United States in the late 19th century. The newest of those is Salsola ryanii, a genetic hybrid of two existing tumbleweed species. Scientists originally thought that S. ryanii wouldn’t thrive because it seemed less well adapted than other species for the hot, dry landscapes of the West. But a recent study in the American Journal of Botany shattered that assumption. Over the course of just 10 years, it had spread from just two sites in California’s San Joaquin Valley to nine sites there and six in other areas, including near San Francisco and Ventura, California. In drought conditions, tumbleweeds can help spread wildfires and can also clog streams and drainage ditches, leading U.S. officials to import tumbleweed-killing viruses from Russia to control their spread.
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