MEPS 577:93-103 (2017)  -  DOI: https://doi.org/10.3354/meps12245

ABSTRACT: Concern about the impacts of invasive species on invaded communities is often linked to the expectation that invasive consumers will be more effective at using resources than native ones. Many invasive marine crabs (infraorder Brachyura) are regarded as particularly capable consumers; however, native crabs can also exert significant influence on community structure. We used marine crabs as a focal group to test whether non-native consumers have greater impacts than native consumers on native prey populations by conducting a systematic review and meta-analysis of 834 crab foraging experiments. In addition to the effect of crab origin (non-native or native) on prey abundance, we examined the effects of interaction type (direct or indirect), prey type, and experimental design. Overall, direct consumption by non-native crabs did not reduce prey abundance more than predation by native crabs, although the magnitude of reductions in prey abundance varied with prey type and experimental design. Indirect interactions with crabs (i.e. through trophic cascades with crabs as the initiators) generally increased the abundance of native species. The direct and indirect impacts of non-native crabs were significantly greater than those of native crabs on primary producers and in simplified experiments with low species diversity. Thus, detecting differences between native and non-native crabs may be heavily influenced by experimental design. Importantly, we found few studies that considered direct interactions (competitive or predatory) between native and non-native crabs. These interactions should be a focus of future research because they could greatly alter consumption rates and overall prey mortality in the wild.

KEY WORDS: Aquatic invasive species · Marine crustaceans · Meta-analysis · Ecological impact · Taxonomic distinctiveness hypothesis