Individual variation in the phenology of oak trees and its consequences for herbivorous insects

1 The growth, fecundity and herbivore communities of 36 trees of Quercus robur L. have been studied for 7 years since 1981, as part of a long term study into the impact of insect herbivory on tree recruitment. 2 Using six phenological categories, assessed daily throughout the spring, it is possible to assign to each tree a unique phenological rank for each year. 3 Trees have consistent phenological ranks from year to year. The same trees are the first into leaf, and the first to shed their leaves in autumn. 4 Contrary to conventional wisdom, early-flushing trees did not suffer significantly higher levels of defoliation. However, the same trees have been consistently the most heavily defoliated, year after year. 5 The date of bud burst in spring can vary by as much as 3 weeks but the time difference between the earliest and latest individuals is almost constant (25 days in our sample of trees). 6 Individuals with different phenology support significantly different herbivore faunas, both in species composition and in relative abundance. 7 The degree of variation between individual plants exhibited in this study is extremely high and emphasizes the need for large sample sizes. It further cautions against generalizations about the composition of herbivore faunas based on samples of few individual plants.