Other experts are still grappling with the question of whether an imperiled species can also be a menace. “How do you deal with the blurriness of that?” Dr. Tessler said.
The waterwheel is not alone in its double life as both ecological victim and environmental menace. In Southeast Asia, the Burmese python has been nearly snuffed out. But in Florida, where the pythons were originally imported as pets, officials are scrambling to keep 20-foot, 200-pound snakes from decimating local animal populations.
In the Great Lakes, conservationists battle invasive sea lampreys, overfished in their home region of southwestern Europe. A large garden bumblebee disappearing in Britain has begun to outcompete native pollinators in Argentina.
Is it possible to reconcile a creature’s double billing in both endangered species catalogs and invasive species indexes?
“It’s kind of the perfect paradox,” Dr. Cross said.
‘A quantum leap in growth’
The waterwheel made its American debut in the mid-1970s after trades between Japanese and American carnivorous plant growers. When growers in Virginia struggled to cultivate the Japanese plants in plastic containers, they introduced them to shallow backyard ponds, according to a 2013 account published in the Journal of the Torrey Botanical Society.
By the late 1990s, waterwheel transplants in five counties in Virginia had flourished into established populations. Around that time, Richard Sivertsen, a well known grower of carnivorous plants, decided to bring it to New Jersey and New York.
In 1999, Mr. Sivertsen (who died in 2017) picked a dozen sites, such as abandoned sand and gravel pits, small ditches and artificial koi ponds, which he deemed sufficiently isolated from pristine wetlands and larger water bodies. Then, having harvested some of the Virginia transplants, he drove around for two days, scattering Aldrovanda like a Tristate Johnny Appleseed.