Positive and negative effects of herbivory on the population dynamics of Senecio jacobaea L. and Cynoglossum officinale L.

摘要: Herbivore effects were studied on populations of the biennial plant species Senecio jacobaea and Cynoglossum officinale. During a three year period (1985–1988) population characteristics (herbivory, number seedlings, rosettes flowering plants) compared in-and outside exclosures, as well parameters reflecting vegetation cover. In S. jacobaea, strong negative effect Tyria jacobaeae was found seedling establishment, rosette growth flowering. On other hand, vertebrate herbivores (mainly rabbits) had an indirect positive by limiting development surrounding (esp. grasses). The increasing cover in protected caused reduction germination, seedling- rosette-growth. Herbivory C. officinale low (<10%), no direct shown. Indirect herbivory through even more pronounced jacobaea. Therefore, although both may first benefit from herbivore-exclusion, their are dependent rabbits eating plants grasses) reducing competition.