Variation in nutritional quality among different-aged foliage can have a large influence on patterns of insect foraging and herbivory within and among plants. Such age-related heterogeneity may be particularly high in conifer, which produce new foliage each year while retaining many older age-classes of foliage. Although several studies have investigated the role of foliage age in shaping patterns of herbivore distribution and abundance within trees, few detailed studies have been carried out in the field to elucidate the underlying mechanisms influencing observed feeding strategies.
In this talk, I will describe results from my previous and ongoing research investigating the influence of age-related variation in foliage nutritional quality within conifers on the fitness and foraging behaviours of both specialist and generalist herbivores in Canada and Japan. Collectively, these studies have demonstrated that juvenile insects employ a variety of foraging strategies to overcome variation in foliage age within conifers, and that the observed foraging behaviours generally lead to higher overall fitness compared to potential alternative strategies. The significance of these results in the context of modern ecological and insect-plant interaction theory will be discussed.