SUCCESSIONAL TRENDS IN INSECT HERBIVORE POPULATION-DENSITIES - A FIELD-TEST OF A HYPOTHESIS

(1) Theory suggests that plants typical of early and late succession s hould possess qualitatively different anti-herbivore chemical defences . Differences in the structure, mode of action and effect of these che micals should result in greater herbivore population levels on plants of early succession. (2) This theory was tested for three separate ins ect taxa over a successional gradient in southern England. (3) All tax a displayed greater population densities on short-lived plants of earl y succession than on birch, a plant of late succession. (4) Although t he results support theories which suggest a dichotomy of effect of the chemical defences of early and late successional plants, difficulties remain in reconciling the theory of plant chemical defences with exis ting data.