Modeling Bythotrephes longimanus invasions in the Great Lakes basin based on its European distribution

Abstract

The predatory cladoceran Bythotrephes longimanus LEYDIG has a natural distribution that extends throughout much of the Palearctic region, and an ever increasing distribution in the Great Lakes basin of North America, where it was first observed in 1982. In this study we define characteristics of 55 waterbodies with and without Bythotrephes in Europe, and use these distributions to predict the species' occurrence in 49 lakes in the Great Lakes basin of North America. Lakes in Europe that supported Bythotrephes were significantly larger, deeper, had higher transparency and lower maximum bottom temperature during summer, and lower total chlorophyll concentration, than those that lacked the species. These patterns also were observed for lakes in North America, although differences between invaded and noninvaded basins were significant only for lake area and maximum depth. A discriminant function model correctly predicted Bythotrephes occurrence in 91 % of study lakes in Europe, and was influenced most by Secchi disk transparency and lake surface area. Application of this model to North America correctly predicted occurrence of Bythotrephes in 82 % (18 of 22) of lakes in which the species has been recorded. However, the model incorrectly predicted Bythotrephes presence in 74 % (20 of 27) of lakes in which the species has not yet been observed. These findings indicate that many of the study lakes in the Great Lakes basin may be vulnerable to invasion by Bythotrephes.