Notre Dame’s Science-Based Tools for Assessing Invasion Risk (STAIR): Mollusks
For this risk assessment, we looked only at what helps species transition from established—reproducing populations causing no discernible harm—to invasive. Because very little information is available on introduced species that failed to become established, we were unable to analyze that transition.
In a previous study, members of our team gathered trait data on each of the 15 established mollusk species in the Great Lakes and used it to develop a tree-based decision tool for determining which established species are likely to cause harm. They found that whether a species will become invasive depends on just one trait: the number of eggs or live offspring released per female per year (annual individual female fecundity). Six of the established species have fecundities greater than 162, and five of these are considered invasive. In contrast, all nine of the established species with fecundities less than 162 have not caused harm.
We have expanded this tool to include additional factors such as climate match with the Great Lakes region, history of invasion elsewhere and whether the species is a carrier of parasites or pathogens of concern.
The original paper identifying fecundity as the driver of mollusk invasions was written by researchers at the University of Notre Dame. Updates to this model have been completed with further work from Notre Dame and Loyola University Chicago.
The quality of any risk assessment depends on the information used to answer the tool’s questions. Using the best available data—scientific journals, species accounts in books, and expert opinion—to answer each question will provide the best results.