Insect Herbivores and Plant Succession

Insect-plant interactions at the community level are discussed in terms of the life-cycle strategies of the insects at different stages in plant succession and the effects of early colonising insect herbivores on the development of the plant community. Insect life-cycle strategies are influenced by habitat permanence, habitat complexity and resource availability and diversity. These factors increase as plant succession proceeds. The life-cycle strategies of insects also change during plant succession with differences in generation time, migratory ability, overwintering stage and reproductive potential. The degree of niche specialisation and the size of the organisms also vary. The characteristic life-cycle strategies of an early colonising species are discussed and the impact of phytophagous species on early successional plant communities found to be considerable. Single species studies (e.g. Raphanus raphanistrum) enable this effect to be assessed more fully. Insect grazing affects the survival, growth and reproductive potential of a plant species. At a community level insect grazing has an effect comparable to that of vertebrates, namely a reduction in the rate of plant succession.