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USF Researcher Aims to Change How We Look at Invasive Species

Worldwide, invasions threaten native species and communities, degrade natural areas, decrease crop yields and cost billions to eradicate. Notorious invasive species such as Burmese pythons, Melaleuca, Cuban tree frogs, and fire ants, have consumed the attention -- and substantial resources -- of Florida and elsewhere.

But despite an exponential increase in the number of studies -- more than 10,000 academic papers on the subject, including a proliferation of more than 20 hypotheses and nearly as many general reviews -- researchers have noted a lack generality in the causal explanations for invasions and very limited success in their control.

This suggests that scientists need to change their thinking, but as one researcher in this field puts it, changing thinking is almost as difficult as eradicating an invasive species.

In an effort to recast the way scientists understand invasions, an international team including Gordon Fox, an associate professor in the University of South Florida's Department of Integrative Biology have developed a new Synthetic Invasion meta-framework that takes scientists back to the basics of how populations change over time and spread through the landscape.

Fox joined with researchers from Stony Brook University in New York, Southwestern University in Texas and researchers at universities in Australia and India in the project, which appears in the April issue of the prestigious international journal Ecology Letters.

"People have worked for the last couple of decades proposing scenarios: we take a plant from Europe that's well-behaved there and it runs amok in Florida. They say it's missing its predators," Fox said.

"What we're saying is if you take a step back and look at the totality of the biology, all these things are multi-causal. There are generally not single explanations for most invasions. The other thing is explaining an invasion is very different than controlling it."

Their paper focuses attention on the key ecological and evolutionary processes known to distill general understanding about the varied and overlapping mechanisms that can cause invasions by various species.

New and sometimes counterintuitive, insights are gained by considering, for instance, how the source and timing of propagule introductions can stimulate or impede a plant invasion, Fox said.

“We believe that a general framework should put the mechanisms and processes contributing to invasion into the context of basic ecology and evolutionary biology," the scientists wrote.

"Population interactions such as competition and predation, ecosystem processes and community and landscape ecology are important basic factors in invasions. Demography of the invading populations is central. The functional ecology, ecosystem, community and landscape processes associated with an invasion must have demographic consequences – increasing the population growth and dispersal of the invader – if they are to contribute to an invasion. Evolutionary processes are integral to a general understanding of invasions, and both the invasive species and the natives in the communities they invade are subject to them."

Other advances from the careful thinking guided by the new framework are that even some deceptively simple explanations may be quite complex, Fox said.

For example, the team shows that an influential hypothesis (that invasive species tend to evolve increased competitive ability) turns out to require at least six causal links. The bottom line is that the team suggests that much progress can be made on invasions by scientists working smarter rather than harder.

"Part of the problem is people have been trying to explain these invasions as if they are different from what we know about ecology and evolutionary biology and it's not," Fox said.