Abstract

Invasion biologists have devoted considerable attention to identifying species characteristics associated with successful biological invasions, as well as attributes that render communities vulnerable to invasion. A shift in paradigms has occurred in recent years, with many biologists now focusing attention on the early phase of invasions when propagules first challenge novel ecosystems. One such model simply predicts invasion success based upon the 'propagule pressure', or introduction effort, exerted on a community by the invasive species. Lakes may be among the best ecosystems to develop these models as borders for these habitats are clearly defined, and vectors delivering propagules usually readily identifiable and quantifiable. We developed a doubly-constrained 'gravity model' to link invaded source lakes with noninvaded destinations. Once the Great Lakes became invaded with Eurasian species (delivered by international ships' ballast water), these species began to spread to inland lakes owing to human activities. By identifying and quantifying these different human-based dispersal mechanisms, we were able to reconstruct the invasion sequence for >30 lakes invaded by the spiny waterflea Bythotrephes longimanus. We were also able to forecast which lakes should be most vulnerable to invasion based upon the amount of vector-traffic inbound to them from invaded, source lakes. Moreover, we were able to determine which lakes can or do serve as 'invasion hubs', greatly increasing spread among interconnected systems. By focusing managerial efforts on these actual or potential hubs, we may be able to dramatically reduce the rate of spread. Vector-based models serve as an excellent starting point for predicting invasion success, and can be further refined by considering biological, chemical or physical characteristics of the species and ecosystems involved.

Biographical Sketch

I completed my PhD in zooplankton ecology at Dartmouth College, and then did a postdoctoral fellowship on invasive species at University of Toronto. I have been a faculty member at the University of Windsor since 1992, and am currently a professor and the Department of Fisheries and Oceans' Aquatic Invasive Species Research Chair at the Great Lakes Institute for Environmental Research.

My research centers on vectors and pathways that transmit invasive species from one region to another. Most of these vectors are associated with human activities, including intercontinental shipping and ballast water discharge, to recreational activities. We use a variety of approaches to study vectors and pathways, including genetic analyses of invasive species populations and their putative sources, modeling, and experimentation. We have major projects on ballast water and sediments on the Great Lakes and Chesapeake Bay, as well as on inland lakes. Once species invade the Great Lakes, human vectors disperse them to inland lakes. By identifying dispersal mechanisms and their relative strengths, we hope to determine the best allocation of management resources to effectively curtail further spread of these species.

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