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5 December 2013 11:26 am ,
Vol. 342 ,
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Hybridizing With the Enemy
7 August 2000 7:00 pm
SNOWBIRD, UTAH--An exotic species of cordgrass is driving a native one out of existence in San Francisco Bay--not just by outcompeting it for light, water, nutrients, or space directly, like most invasive species, but also by letting hybrids do the dirty work. Cross-pollination between the two species is rare, researchers reported here on 6 August at the annual meeting of the Ecological Society of America, but once it happens, the resulting hybrids mate much more readily with the natives, enabling them to take over the population quickly.
The fast-growing grass Spartina alterniflora, a native of the eastern United States, was deliberately introduced to three salt marshes in San Francisco Bay in the mid-1970s. Now, the less hardy native cordgrass S. foliosa has been crowded out of many tidal creeks and channels on the southern side of the bay--not just by S. alterniflora, but also by hybrids between the two species. "The amount of hybridization surprised us all," says Debra Ayres, an ecologist at the University of California, Davis. The results have been devastating: Sparsely vegetated mudflats that used to host thousands of migrating shorebirds have been replaced by densely vegetated meadows of 2-meter-tall S. alterniflora and its hybrids.
To understand how the eastern cordgrass imposes itself on its western relatives, Ayres and her colleague Donald Strong first checked the flowering times for the two species. There was hardly any overlap, causing hybridization to be almost impossible. However, if hybridization does occur, the rest is easy. The researchers found that the flowering time for hybrid plants overlaps with the natives', making cross-pollination a breeze.
And that's happening in the salt marshes. When the team analyzed nuclear DNA from 547 seeds gathered from native plants living at a newly invaded site near Tiburon, California, they found that none of the seeds were the result of cross-pollination between the native and alien species, but 11% of the seeds had a hybrid for a parent. The culprit, Ayres says, is "not the alien itself, but its evil spawn."
"It's excellent work and evidence of how difficult, if not impossible, it may be to control many invasive species," says David Policansky, an evolutionary ecologist at the National Research Council in Washington, D.C. In addition, he says, the DNA analysis "shows the importance of understanding the genetics of the system you are working with."
Marine Science Institute; focuses on San Francisco Bay and has information on introduced species