EFFECTS OF HERBIVORY AND GENOTYPE ON GROWTH AND SURVIVORSHIP OF SAND-DUNE WILLOW (SALIX-CORDATA)

1. The response of different clones of sand-dune willow, Salix cordata, to herbivory by a specialist herbivore, Altica subplicata, was studied in three glasshouse experiments. Plants were caged and exposed to three herbivory treatments: no beetles, low number of beetles, and high number of beetles. 2. Plants consistently had significantly higher growth rates in the absence of herbivory than under conditions of low or high herbivory (1.5-6 times higher). 3. Herbivore treatment influenced mortality from drought stress; more plants from the low and high herbivory treatments (40% and 80%) died from drought stress than did control plants (0%). 4. Clone genotype significantly influenced growth rates and the susceptibility of plants to drought stress. However, clones showed similar growth responses to herbivory, suggesting a lack of genetic variation in tolerance or resistance to herbivory.