Ecologists generally believe the world’s worst invasive species have an "away-field advantage," meaning they do better in their new territories than at home. A new study led by Smithsonian scientists reveals this assumption is not always the case.

The away-field advantage idea assumes there is a fundamental difference between the native and introduced range that enables invaders to succeed. For example they may encounter fewer natural enemies, more unsuspecting prey or weaker competitors.

"They’ve been presumed to be good citizens at home and bad citizens away," said ecologist John Parker of the Smithsonian Environmental Research Center, first author of the paper in the May issue of the journal Ecology.

The European green crab, which has spread around the globe, is one of the "world’s worst" invasive species include in a recent Smithsonian research paper that evaluates the performance of invasive species in their new territories. Photo by Todd Huspeni

Authors, including STRI scientist Mark Torchin, compared data on native and introduced populations of 53 species of invasive plants and animals. They found that while many invaders - mostly plants - perform better, about half of all species perform similarly at home and abroad. Some do worse.

"There was extensive variation both within and across species, suggesting that different mechanisms probably interact to drive invasion success," says Mark, who hosted the 2010 Global Invasions Network meeting at STRI that sparked the research paper.