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

Abstract

The impacts of invasive alien species are greatest when they become dominant members of a community,introduce novel traits, and displace native species. Invasions by alien mollusks represent a novel contextby which to compare trait differences between generalist native and introduced herbivores in terrestrialecosystems. Here, we determined the abundance, habitat, feeding preferences, as well as the metabolicrate of the native Pacific banana slug (Ariolimax columbianus) and the alien black slug (Arion rufus) in thecoastal forests of British Columbia, Canada. Through a series of observational and experimental studies,we found that alien slugs are more abundant, differ in their habitat preferences, and consumed more fungi(mushrooms) than native banana slugs. Conversely, in an enclosures experiment we found that herbivorydamage by native slugs was higher compared to enclosures with alien only and control enclosures. Finally,metabolic rates were similar for both slug species. These results suggest that alien black slugs possess a suiteof traits that make them functionally different from native banana slugs.