Beneficial invaders?

What comes to mind when you hear the words, “non-native species”? You likely conjure images of dead zebra mussels littering the shores of the Great Lakes in the Midwestern United States, or perhaps you imagine invasive bullfrogs chowing down on native red-legged frogs in California. Typically, we associate non-native species with dramatic, overabundant population sizes and decimation of charismatic native fauna. However, scientists have begun to distinguish between “good” and “bad” effects of non-natives. An emergent area of research in invasion ecology aims to answer the questions: are non-native species all “bad”, and under what circumstances are introduced species beneficial to people or the environment?

Although non-native species are often anathema to people who care about the environment, familiar examples of beneficial invaders abound. Think of honey bees pollinating agricultural crops and cattle that provide us with milk (and ice cream!). But beneficial invaders go beyond agriculturally important species. A review article published in 2011 (Schlaepfer et al. 2011) that Julian co-authored highlights some of the ecosystem services provided by non-native species, including providing food and habitat for native species and substituting functionally for species that have gone extinct.

The Olden lab continues to pursue research that explores the potential benefits of non-native species. During the summer of 2012 I sampled the fish and invertebrate communities of lakes in the Puget Sound region of Washington State with the goal of determining whether the introduced Chinese Mystery snail is “good” or “bad” for lake food webs. The Chinese Mystery Snail was first brought from Asia to the San Francisco Bay region over 40 years ago for culinary use. It has since been introduced to lakes and reservoirs in the southeastern U.S., the Midwest, and the Pacific Northwest. Little is known about these large (and mysterious) snails. However, snails are a common prey item for many aquatic animals including fishes, crayfish, and water birds. In fact, feeding experiments by the Olden lab showed that Signal Crayfish, native to Washington, readily consume Chinese Mystery snails. In addition, many lakes in the Puget Sound area have undergone extensive development for human residences and recreation that have left native invertebrate prey scarce. Thus, the Chinese Mystery snail may provide an important prey resource for the fish and crayfish that many Washington residents enjoy.

While it is too soon to determine the role of the Chinese Mystery Snail in Washington lakes, the Olden lab’s research will contribute to the body of scientific research that is concerned with the net effects of invaders. Understanding whether non-native species cause net harm or good will enable us to better manage new species introductions; emerging research will enable decisions on whether to remove harmful invaders or allow beneficial ones to persist in their new environment.

- Laura Twardochleb