Biological mechanisms of marine invasions

With expanding trade resulting in increased global transport of non-native species, a broader understanding of the mechanisms of marine invasions is becoming increasingly crucial. Yet our understanding of marine invasions lags behind that of terrestrial invasions, and this includes our understanding of fundamental biological mechanisms that influence marine invasion success. We used a systematic search of over 3000 peer-reviewed papers to review the marine invasion literature, identify overarching patterns, and help direct future research. We focus on 4 biological mechanisms: negative interactions (e.g. limiting similarity, biotic resistance, enemy release, novel weapons), positive interactions, invader traits, and post-introduction evolution, as they relate to understanding marine invasion success. A total of 470 studies (264 non-native species) were reviewed, resulting in the largest review of biological mechanisms of marine invasions to date. Negative interactions and invader traits received the majority of attention in the literature. Most negative interaction studies documented an increase in invasion success resulting from avoidance or release from competitors or consumer pressure. Consumer pressure, and predation in particular, compared to competition was more commonly documented as a mechanism that can limit invasion success. Despite limited evaluation, positive interactions and post-introduction evolution showed potential for enhancing invasion success. Invader trait studies highlighted the importance of life history and stress tolerance traits. Future studies that examine interactions at multiple scales and utilize multi-faceted approaches, molecular techniques, and predictive modeling will enhance our knowledge and ability to develop strategies to protect native ecosystems.