The Interface between Slugs and Wild Ginger: Some Evolutionary Aspects

Data collected on natural populations of Asarum caudatum in western Washington indicated that populations were polymorphic for growth rate, seed production, and palatability to a native slug. However, in habitats where slugs were not as abundant, populations of wild ginger were dominated by individuals allocating more energy to growth rate and seed production, and less to the production of an antiherbivore mechanism. On the basis of these data, I postulated that in the absence of grazing pressure, palatable, faster growing individuals would be at a competitive advantage over slower growing individuals that devote more energy to an antiherbivore mechanism. Under grazing pressure, however, fitness of the unpalatable individuals would be increased since smaller amounts of photosynthetic tissue would be consumed.