Monday, August 6, 2007: 3:20 PM
San Carlos I, San Jose Hilton
Invasion ecology has come a long way, but is still faced with a number of issues that need to be resolved. One potentially powerful approach to expanding our knowledge of the process of invasion is through a comparative, common-garden study of plants obtained from native versus invasive populations. Generally, these studies have been conducted in one garden location, although recent evidence suggests that results from one garden may vary significantly from results in another. Clearly, we need to develop an understanding of the generality of results obtained from common garden studies. The current study examined the response of Lythrum salicaria L. (purple loosestrife) collected from native (European) and invasive (U.S.) populations to varying levels of water and nutrients in four common gardens located in Ames, IA, Newark, NJ, Potsdam, Germany and Tübingen, Germany. The experiment was a full factorial design run in parallel in all four sites. Regular censuses were conducted measuring a number of morphological traits, e.g., height, number of branches, number of stems, and rates of herbivory. At the end of the growing season additional information was obtained for flowering characteristics and production of above ground biomass partitioned between vegetative and reproductive portions of the plant. The response of plants to the treatment combinations were complex, depending upon garden, treatment combination, and source population, with high level interactions exhibiting a significant impact on the outcome of the experiment. Our study suggests that extreme caution should be exercised in extrapolating results from a single garden into a broader context.