Issues : Figure Sets


      In this Issue, students will examine published data that address the ecological consequences of introduced species. Activities engage students in data analysis and hypothesis testing and will increase their understanding of the complexities of ecological phenomena. This Issue focuses on ecological consequences of introduced species using several case studies - zebra mussels, brown tree snakes, fire ants, and gypsy moths. There are many, many more examples of introduced species; faculty looking for others can use links in the resources section and this Issue for ideas about how to help students think about this complex and controversial topic. Note that the ESA Issues in Ecology No. 5 is called Biotic Invasions: Epidemiology, Global Consequences and Control (http://www.esa.org/sbi/sbi_issues/). As with all TIEE Issues the teaching approaches suggested here are just that - suggestions. Adopt and modify as suits your needs.

      As the ecology of introductions become better understood, ecological information about this phenomenon can help address management issues and perhaps mitigate ecological disruption from species introductions in the future. Decreasing the rate and impacts of introduced species is considered by many as important to maintaining the natural biodiversity and ecosystem functioning which, in turn, provide goods and services for humans (see ESA's Issues in Ecology No. 2: Ecosystem Services and No. 4: Biodiversity and Ecosystem Functioning; http://www.esa.org/sbi/sbi_issues/). As expected, ecologists disagree about effects of introductions, including the relationship between diversity of introduced species and native ones (Rejimanek 2003).

      The relocation of organisms across geographical boundaries occurs naturally by various means. Since humans began exploring the globe, however, the rate of new species being introduced into regions has greatly increased. In some cases, humans have dispersed species on purpose; for instance, many plants were transported from Europe to North America for agricultural and ornamental purposes. Others were transported accidentally by ship, train, airplane - even on the shoes of hikers.

      Some species may be introduced and not be able to survive in their new habitat. Others may find optimal conditions for growing, reproducing, and adapting to the new environment, and their populations soar. For instance, lack of predators may contribute to their rapid population increases.

      Not surprisingly, there is much controversy about the topic of introduced species. This includes debate about the terms "invasive", "exotic", "introduced" and "native". If a plant such as Kentucky bluegrass was introduced to Illinois 200 years ago, is it native or introduced (http://www.invasivespecies.gov/, http://www.farmlandinfo.org/fic/states/il/grass/kentuckybluegrass.html)? What about organisms that "invade" new volcanic islands like Krakatoa? Are they native?

      One way to clarify the terminology is to consider the effects of the species. Introduced species that have profound effects on their new ecosystems have been termed invasive species. These effects include outcompeting native species, sometimes causing their extinction, and altering ecosystem functioning.

      The activities presented in this Issue investigate the ecological disturbances created by four introduced species and the research conducted to better understand their ecology and effects.


Web Resources:

Zebra Mussel

Brown Tree Snake

Fire Ant

Gypsy Moth