Organisms that modify or create habitat are considered ecosystem engineers if their activity substantially alters the availability of resources to a large number of other species. For example, dam building by beavers can raise the local water table and create habitat suitable for wetland, riparian, and aquatic plants. In addition to modifying habitat, ecosystem engineers are also likely to be competitors, prey, and/or predators. Experimental manipulations of earthworms, considered ecosystem engineers in the habitat where the experiments will be conducted, and salamanders, another common species in the same habitat, will be used to simultaneously examine the effect on salamanders of habitat modification by earthworms, the role of earthworms as a food source for salamanders, and the effect of earthworms as indirect competitors of salamanders. Consequences of replacing a native species with an invasive species will be examined by testing both native and non-native earthworm species. The novelty of this project is that it simultaneously incorporates ecosystem engineering, direct predatory, and indirect competitive effects within a single experimental design in a way that the magnitude of the individual effects can be compared. In addition, the research will further scientific understanding of the role of ecologically similar native and non-native ecosystem engineers in ecological communities. This project will provide funding for a PhD student and facilitate the teaching and training of undergraduate students. The project will include outreach to high school students and undergraduate students, demonstrating earthworm extraction methods and using this as a springboard to explain the history and ubiquity of non-native species in North America.
