Individual host taxa may resist the climate-mediated trend in herbivory: Cenozoic herbivory patterns in western North American oaks

Examination of leaves from thirteen floras from the western United States shows that neither mean annual temperature nor average precipitation was a significant determinant of overall insect damage. However, herbivory made by endophagous insects (gallers and leaf miners) was more prevalent in dry conditions. Temperature also was a significant determinant of gall and leaf mine damage; warmer floras tended to have more galls and fewer leaf mines. In addition, gallers and leaf miners show a high degree of host-fidelity through time. This pattern of host-fidelity suggests that feeding of endophagous insect herbivores is more climatically sensitive than that of more generalized, exophagous herbivores, and that future climatic change may not affect all host-herbivore systems, nor all herbivores within a single host system, in the same ways. Therefore, an increase in outbreaks of specialized insects on their hosts may be more likely than broadly increased herbivory as global temperatures increase.