Comparing functional similarity between a native and an alien slug in temperate rain forests of British Columbia

The impacts of invasive alienspecies are greatest when they become dominant members of a community, introduce novel traits, and displace nativespecies. Invasions by alienmollusks represent a novel context by which to compare trait differences between generalist nativeand introduced herbivores in terrestrial ecosystems. Here, we determined the abundance, habitat, feeding preferences, as well as the metabolic rate of the nativePacific banana slug( Ariolimax columbianus) and the alien black slug( Arionrufus) in the coastal forests of British Columbia, Canada. Through a series of observational and experimental studies, we found that alien slugsare more abundant, differ in their habitat preferences, and consumed more fungi (mushrooms) than native banana slugs. Conversely, in an enclosuresexperiment we found that herbivory damage by native slugswas higher compared to enclosureswith alienonly and control enclosures. Finally, metabolic rates were similar for both slugspecies. These results suggest that alien black slugspossess a suite of traits that make them functionally different from native banana slugs.