"Our study is the first to document hybridization associated with the invasion and displacement of resident crayfish species," say William Perry, who did this work while at the University of Notre Dame in Indiana and is now at Illinois State University in Normal, Illinois, and his colleagues in the December issue of Conservation Biology.

Hybridization has been implicated in the decline of many imperiled species, from North American sunflowers to Hawaiian ducks to red wolves. Perry and his colleagues suggest that hybridization may play an even larger role in non-native species invasions than biologists had realized.

North American freshwater animals are estimated to have the highest extinction rates in the world, and nearly a third of our 390 crayfish species are at-risk. One of the biggest threats to local crayfish is the introduction of the rusty crayfish, which is widely used as fishing bait. Native to Ohio, Kentucky and Indiana, the rusty crayfish has spread as far as Maine, New Mexico and Tennessee.

The rusty crayfish was introduced to northern Wisconsin and Michigan lakes in the 1960s, where it is displacing the northern clearwater crayfish and other local species.

Although the rusty crayfish and the northern clearwater crayfish are both native to North America, they are not ecologically equivalent. Crayfish are critical to their ecosystems and changes in the crayfish community can have severe impacts on lakes and streams. For instance, in northern Wisconsin lakes, introduced rusty crayfish have clearcut the bottom-growing aquatic weeds that provide a refuge for fish and invertebrates. Moreover, the rusty crayfish
'"/>

Contact: William Perry
wlperry@ilstu.edu
309-438-8176
Society for Conservation Biology
30-Nov-2001