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Invasive species have transformed marine habitatsaround the world. The most harmful of these invaders displace native species, change community structure and food webs, and alter fundamental processes, such as nutri-ent cycling and sedimentation. Alien invasives have damaged economies by diminishing fisheries, fouling ships ’ hulls, and clogging intake pipes. Some can even directly impact human health by causing disease (Ruiz et al. 1997). Although only a small fraction of the many marine species introduced outside of their native range are able to thrive and invade new habitats (Mack et al. 2000), their impact can be dramatic. The impacts of invasions may be seen locally, but the drivers of biological invasion are, to an increasing degree, global. Unfortunately, there is a paucity of infor-mation on invasive species at the global scale. Th