DEMOGRAPHY OF THE PERENNIAL HERB LATHYRUS-VERNUS .1. HERBIVORY AND INDIVIDUAL-PERFORMANCE

1 The pattern of three types of herbivory, meristem damage by molluscs, grazing by roe deer and leaf damage by invertebrates, and their effects on survival, growth and fruit production in the perennial herb Lathyrus vernus were examined in 11 plots in east Sweden during 4 seasons. 2 All three types of herbivory varied among plots but only leaf damage varied among years. Within patches, the amounts of grazing and leaf damage were size-dependent although no type of damage increased with decreased inter-neighbour distance. Once an individual had suffered meristem or leaf damage there was an increased risk of the same kind of damage occurring in the following year. 3 Damage of meristems and vertebrate grazing reduced survival, growth and fruit production of L. vernus individuals. Leaf damage reduced only survival and fruit production. 4 Meristem damage by molluscs had the most severe effects on the performance of L. vernus individuals in contrast to the general proposition that vertebrates and insects are the most important herbivores. This may be because such attacks delay the onset of assimilation thus missing part of the most favourable growing season.