An influx of invasive species can stop the usual natural process of new species formation and can trigger mass extinction events, a U.S. researcher says.
Alycia Stigall, a scientist at Ohio University, has been studying a collapse of Earth's marine life 378 million to 375 million years ago, in the Late Devonian period, an extinction unlike any other in the planet's history, a National Science Foundation release said Wednesday.
In that prehistoric event, the number of extinctions wasn't higher than the natural rate of species loss, but what puzzled scientists is that very few new species arose.
"We refer to the Late Devonian as a mass extinction, but it was actually a biodiversity crisis," Stigall says.
Her research suggests the usual method by which new species originate, known as vicariance, was absent during this ancient phase of Earth's history.
Vicariance occurs when a population becomes geographically divided by a natural, long-term event, such as the formation of a mountain range or a new river channel, and evolves into different species.
As continents closed in to form connected land masses during the Devonian, some species gained access to environments they hadn't inhabited before. The hardiest of these invasive species became dominant, wiping out more locally adapted species.
The invasive species were so prolific it became difficult for many new species to arise, Stigall says.
"The main mode of speciation that occurs in the geological record is shut down during the Devonian," she says. "It just stops in its tracks."
The study is relevant for the current biodiversity crisis as human activity has introduced a high number of invasive species into new ecosystems, she says.
"The more we know about this process," she says, "the more we will understand how to best preserve biodiversity."