DNA Used to Track Renegade Pond Weed

From the USGS: New DNA Tool Helps Scientists Identify Invasive Species of Aquatic Plants

A new DNA protocol developed by the U.S. Geological Survey helps biologists distinguish between native and invasive species of aquatic vegetation that have almost identical appearances. Until now, measuring the dispersal of these various invasive plants has been hampered by confusion about where and when the plants arrived.

Invasive aquatic plants from Korea, Brazil, and the Indian subcontinent have been spreading through U.S. waterways for decades. The new DNA protocol will help biologists identify species, track their progress, and provide facts to local managers who can develop appropriate control measures.

“When invasive plants appear in a body of water, local people naturally are alarmed” said Nancy Rybicki, the USGS biologist who teamed up with molecular biologists to develop the new DNA testing technique. “Enormous amounts of money are spent on control. Some species may look very nearly identical, but they have unique reproductive and growth characteristics. Identification, the first step for control or eradication, needs to be precise.”

Using this new protocol, Rybicki determined that hydrilla arrived in both the Potomac River and Chesapeake Bay earlier than previously thought, a finding that revises earlier ideas of how it was first introduced into the area.

The authors found that hydrilla was in the Potomac River in 1976. Thus, the original introduction of hydrilla to the Potomac was not from National Park Service experiments conducted in 1980 at Dyke Marsh on the tidal Potomac River as previously thought. It is probable that hydrilla was already present, but was misidentified. It may still be undiscovered in many locations today.

Huge beds of Hydrilla are widely credited with helping to clean up portions of the Potomac River. And they make good habitat for another invader, the Chinese Snakehead.

The two biotypes of hydrilla, one first introduced into Florida and the other first introduced into Washington, DC, are both spreading toward Canada, well beyond their predicted range.

“We anticipate that hydrilla will continue to move into colder regions, including, the Great Lakes, where a native plant called elodea is common,” Rybicki explained. “Without DNA verification, misidentification of the two plants is likely.”

New technologies are nice, but it's kind of sad when it gets to where scientists are relying on DNA tests instead of whipping out the cheap dichotomous key and learning what traits distinguish the two species.