RESPONSES OF BRAMBLES, RUBUS-VESTITUS, TO HERBIVORY

We investigated the effect of fertilisation and multiple episodes of s imulated herbivory on the prickliness of bramble, Rubus vestitus. The prickliness of fertilised, uncut plants was significantly greater than that of plants in all other treatments. Our results indicate that pri ckle production is constrained by resource availability, with brambles allocating resources to growth under intense herbivory. Isozyme elect rophoresis of plants collected from Wytham Woods, Oxford, UK, failed t o detect any variation, suggesting that observed variation in pricklin ess may be primarily the result of phenotypic plasticity. In our exper iments, however, we observed significant variation in prickliness amon g putative genotypes.