RUI: Geographic Variation in Activated Antiherbivore Defenses

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The goals of this research are to assess the effectiveness of an activated anti-herbivore chemical defense system in algae, and to identify geographic trends in these defenses. In this defense system, dimethylsulfonioproprionate (DMSP) produced by the algae is converted with the enzyme DMSP lyase, to dimethyl sulfide (DMS) and acrylic acid when the plant is damaged by herbivores. Both DMS and acrylic acid can be potent feeding deterrents. Because grazing pressures are generally thought to be higher at lower latitudes than at higher latitudes, the PI will measure the production of DMSP and DMSP lyase from algae in four regions: the temperate northeastern Pacific region, the temperate Southern Pacific region, the tropical Pacific region, and the tropical Atlantic region. In each region, the investigators will assess the effectiveness of the DMSP activated defense system on local herbivores and the effects of changes in environmental factors such as temperature, nutrients, and ultraviolet light, on the production of DMSP and DMSP lyase. The results of this study will provide information on how chemical defenses and plant-herbivore interactions have evolved in different parts of the world, how they vary over space and time, and how they are affected by changes in the environment. This research will provide training opportunities for several undergraduate and master's level students during each year of the project. Over a dozen students will be involved in all aspects of the work and will receive valuable training in state-of-the-art analytical methods, experimental design concepts, statistical analyses, and the use of computer programs for analyzing data and presenting the results of their work to other scientists.