Invasive species can trigger mass extinction
Invasive species are becoming more rampant today as a result of climate change and other factors. Changes in precipitation and temperature patterns often favor invasives, which have an uncanny ability to adapt and spread in stressed ecosystems.
A new study shows how invasives can actually trigger a mass extinction similar, perhaps, to what we’re seeing under modern day biodiversity loss. Geologist Alycia Stigall at Ohio University explored the late Devonian extinction, one of five mass extinctions in Earth history about 378 to 375 million years ago.
During the Devonian, sea levels rose and two continents, Euramerica and Gondwana, closed in to form the single land mass of Pangea. In the process, certain species gained access to new ecosystems, thriving in ways that out-competed the natives.
Stigall claims that the extinction rate during the late Devonia was actually not all that different than background levels. Instead, she looks at the loss of species from the standpoint of speciation. In other words, the creation of new species through subdivisions in populations and dispersals to new territories.
Examining the lifeline (or clade) of three types of shelled invertebrates and a predatory crustacean, she found that the creation of new species through subdivisions in the population — called vicariance — was almost non-existent during this time period. This is unusual compared to other geologic periods and points to the invasion of certain species as the cause for biodiversity loss in the Devonian, she claims. As species went extinct, no daughter species filled the ecological niches left open.
Stigall writes that modern day extinctions may be the result ofÂ a similar situation as human-induced invasive species take over ecosystems leaving few opportunities for natives to adapt.