In 1890, a pharmacist named Eugene Schieffelin released some 60 European starlings into New York's Central Park. He did so because the group he was part of, the
American Acclimatization Society, wanted to make it so that the the skies of North America were filled with the sights and sounds of all the birds mentioned in the works of William Shakespeare.
Schieffelin and company got their wish and then some.
More than 100 years later, the European starling is everywhere, including Toronto. Free of its ancestral predators, the species has managed to grow unchecked,
much to the detriment of North America's native wildlife and even to human activities like farming.
However, the European starling is only the most famous example of an invasive species being introduced to North America. Either by design or mistake, countless other non-native plants and animals have found their way into North America.
One such species is the European fire ant (m
yrmica rubra, for those that enjoy their Latin taxonomies). Colonies of this aggressive ant are often found near water, and they've become a common sight in the Don Valley and on the Toronto Island. A chance encounter with one of these ants often ends with a nasty bite.
What could be worse, is that this ant—and other invasive species like it—could be working together with other invaders to increase the rate at which they both spread across a new ecological system.
Megan Frederickson, an associate professor at the University of Toronto's Department of Ecology and Evolutionary Biology, and Kirsten Prior, a biology professor at the University of Florida, as well several postdoctoral fellows have spent the past year studying the European fire ant.
On a UofT-owned nature reserve an hour north of the city, the researchers used 42 plastic kiddie pools (pictured) to create siloed ecosystems. They filled each pool with soil and the seeds four different species of wildflowers—three of which were native to Ontario, and one, the greater celandine plant, which was not. They then released the European fire ant in about half of the pools and a native woodland ant in the other half, and let them go about their work over the winter.
When the team returned in the spring and summer, they found that the fire ants had dispersed all the species of wildflowers, but particularly the invasive greater celandine plant, to far greater effect than their North American cousins.
This finding seems to in part validate a theory called invasional meltdown, which suggests that the establishment of one invasive species can help facilitate the incursion of other non-native species.
“I’d say we have really good evidence for half of the story. Our experiment very clearly shows that this invasive species, the european fire ant, can help this invasive plant spread,” says Professor Frederickson. “What we don’t know if the reverse is also true.”
Frederickson and her team are working towards seeing if the greater celandine plant somehow helped the fire ants.
The term invasional meltdown was coined by evolutionary biologists Daniel Simberloff and Betsy Von Holle in a seminal 1999 paper.
“Since they wrote this paper in 1999 people have been interested in looking for examples, and there are a handful examples out there but not a whole lot. There’s some debate in the field on how common and important this phenomenon might be—and it's one of the reasons we were interested in doing this study,” says Professor Frederickson.
In the press release that announced the study's findings, Professor Frederickson's colleague Kirsten Prior succinctly stressed the importance of their research. “Invasive species are a leading threat to natural ecosystems, and can have impacts on society,” she said.
“Research on how ecosystems become invaded and the consequences of invasion is important. It sets us on the right path to develop solutions to reduce the spread and impact of these harmful species.”
Source: University of Toronto
Photos: J.G. Sanders, K.M..Prior.