Richard A. Kerr. February 10, 2012.More Than One Way for Invaders to Wreak Havoc.   Science: Vol. 335:646

Ravenous pythons and anacondas invading the Florida Everglades are ravaging the local ecology. But a study published last month suggests that invasive species can have a more insidious effect on natural systems.

About 380 million years ago in the Devonian period, invasive species reigned rampant in the world ocean as the number of marine animal species plummeted. That ecological crisis has been classed as one of the Big Five mass extinctions. But paleontologists think the main problem was not that existing species died out but that new ones failed to form. And the new paper—published in the January issue of GSA Today—holds invasions responsible for that failure to speciate, at least in some marine animal groups.

The new look at the Devonian “has hit on something very interesting,” says paleontologist George McGhee of Rutgers University in Piscataway, New Jersey. “We don’t know where modern invasives will lead us,” McGhee says, but the study raises the possibility that recovering from the current human-induced mass extinction could be much more difficult than thought.

Her deep-time study holds timely lessons for modern humans, Stigall says. Loss of habitat and the introduction of new predators and diseases may be driving the current mass extinction, she says, but “we’re looking at a worse outcome than currently predicted.” Whenever the human-induced mass extinction has run its course, invasives will be seriously inhibiting the creation of new species and retarding recovery. And the greater vulnerability of specialist species compared with generalists means that “even if tremendous resources are devoted to [specialist] species, they probably won’t be sustained in the long term.” Given limited resources, she says, conservationists should give more-resilient species in the middle range the highest priority.