Reassessment of species invasions concepts: the Great Lakes basin as a model

The Laurentian Great Lakes have an extensive history of species introductions, many of which occurred as a result of ballast water discharge by trans-oceanic ships. Most nonindigenous species (NIS) of animals and protozoans that established in the Great Lakes since 1985 are native to the Black, Azov and Caspian Seas or other regions of Eurasia. Analysis of vector strength from global port regions indicates that these NIS, which include amphipods, crustacean zooplankton, mussels and fishes, have been transported principally along dominant shipping routes from native or introduced habitats in northern and western Europe to the Great Lakes. A large group of additional taxa, many of which have extensive invasion histories, is available for transfer to the Great Lakes from key European ports. Thus, joint consideration of invasion corridors and the NIS species established in key donor ports provides an indication of taxa that may colonize the Great Lakes in future. Recent studies indicate that risk assessment may be extended even further for inland lakes subject to NIS invasion from the Great Lakes in cases where invasion vectors can be identified and quantified. Identification of invasion corridors and quantification of vector pathways, using lakes as model systems, provide a promising opportunity for the evolution of invasion biology from a largely descriptive science into a more predictive and quantitative discipline.