Genetic adaptationheritable changes that alter an organisms performancemay facilitate invasion at several scales, but is seldom considered in predicting and managing marine invasions. However, a growing body of researchlargely based on emerging genetic approachessuggests that adaptation is possible and potentially widespread in the marine realm. Here, I review evidence for adaptation in marine invasion, considering both quantitative and genetic studies. Quantitative studies, which consider trait-based differences between populations or individuals without directly examining genetic makeup, have suggested local adaptation in several high-profile species. This implies that invasion risk may not be constant from population to population within a species, a key assumption of most invasion models. However, in many quantitative studies, the effects of heritable adaptive changes may be confounded with the effects of plasticity. Molecular approaches can help disentangle these effects, and studies at the genomic level are beginning to elucidate the specific genetic patterns and pathways underlying adaptation in invasion. While studies at this scale are currently rare in the marine invasion literature, they are likely to become increasingly prevalentand usefulnow that next-generation sequencing approaches have become tractable in non-model systems. Both traditional and emerging genetic approaches can improve our understanding of adaptation in marine invasions, and can aid managers in making accurate predictions of invasion spread and risk.
