DISSERTATION RESEARCH: The role of natural enemies and resource availability in biological invasions by plants

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One likely reason that some of the plant species introduced by humans to new regions are able to spread and outcompete native plants is that the introduced plants are relatively free from natural enemies such as herbivores and pathogens. However, the benefits to an introduced species of release from enemies may depend on the levels of resources such as soil nutrients in the new habitat. In more fertile habitats, many plants grow more rapidly and lower their chemical or physical defenses against enemies. This should increase the advantage of the absence of enemies and thus the ability of introduced plants to outcompete native ones. This project will test this resource-enemy release hypothesis of biological invasion through a series of experiments in which 6 introduced species and 14 native species are grown at different levels of soil fertility and with and without protection from native insect herbivores and fungal pathogens. Understanding the factors that allow some introduced species to become dominant in their new ranges is critical for natural resource management. Invasive species cause declines in biodiversity and cost the U.S. economy nearly $120 billion annually. Results from this project will help managers target control to the habitats and species most at risk. The project will also provide hands-on research experience in field and laboratory settings to several undergraduate students, and disseminate findings to high school biology classes and the local community.