Invasive Species May Spread Via Wildlife Corridors

Invasive species such as fire ants may be able to spread via wildlife corridors - strips of land used to reconnect habitats separated by human activity - according to a new study.

Wildlife corridors are supposed to promote biodiversity, but researchers from the University of California show that they in fact can sometimes be a sort of gateway to the spread of invasive species.

The findings, published in the journal Ecology, are particularly relevant to Florida, where invasive species like Cuban tree frogs, green iguanas and feral hogs are considered a serious ecological problem.

"Although habitat corridors are usually beneficial, they occasionally have negative effects," Julian Resasco, the study's lead author, said in a statement. "Sometimes they can help invasive species spread in exactly the same way they help native species."

The challenge for ecologists, Resasco says, is figuring how when certain invasive species can benefit from these wildlife corridors.

The researchers were initially surprised by their findings because they assumed that invasive species could easily invade a new area without the help of corridors to get around. It turns out that fire ants are an exception to this preconceived notion.

Resasco and his team studied eight sections of land in South Carolina, each dominated by two social forms of fire ants: monogyne and polygyne.

Each section consisted of five patches of regenerating habitat about the size of a football field. And because some were connected by corridors and others were not, researchers could easily determine the influence corridors have on this invasive species.

They found that the presence of the corridors significantly increased the population of polygyne fire ants, which mate closer to the ground and sometimes travel short distances to create new colonies. The research team also found that, due to the higher number of fire ants, the diversity of native ant species was lower in polygyne patches connected by corridors.

"It is not a coincidence that the readily dispersing monogyne form of fire ants doesn't benefit from corridors, whereas the poorly dispersing polygyne form does," Resasco said.

Resasco urges land managers to consider animals' traits when making decisions about land corridors, given that their good intentions could backfire and also aid the spread of invasive species.