DOI: 10.5061/dryad.tc3177n
title: Data from: Climate and leaf traits, not latitude, explain variation in plant‐herbivore interactions across a species’ range

description: 1. Spatial variation in abiotic and biotic factors creates local contexts
 that influence the intensity of plant‐herbivore interactions. Some
 previous studies have accounted for the complexity of these interactions
 with latitudinal clines, while the absence of such clines in many other
 systems suggests other, often unknown, local community factors may instead
 explain the variation in herbivory across populations. 2. We investigated
 plant‐herbivore interactions across the entire range of a long‐lived tree
 (Quercus garryana), evaluating the relative importance of climate,
 latitude, population size, and insect feeding guilds in determining leaf
 phenotype and the extent and variation in insect herbivory. In this
 ecosystem, rain shadows create a nonlinear relationship between climate
 and latitude, allowing us to disentangle the effects of environmental
 factors. By performing similar analyses on trees grown in a common garden,
 we were able to assess the relative importance of environmental factors to
 leaf defence traits and herbivory. 3. Total herbivory varied significantly
 among populations, and was best explained by variation in spring
 precipitation, leaf traits, and tree population size, but not latitude.
 The relative importance of each of these factors changed over the growing
 season and with insect feeding guild. Conversely, damage in the common
 garden did not vary among trees from different origins when grown in a
 constant environment, leading us to believe variation in damage in natural
 populations is more likely the result of the local environments. 4. Leaf
 traits (trichome density and specific leaf area) varied significantly
 among populations, but neither showed an effect of latitude. Variation in
 both traits was best explained by tree size, and seasonal temperatures or
 precipitation. We found no variation in insect diversity among field
 populations, but abundance varied with mean summer precipitation and
 population size. 5. Synthesis: Seasonal precipitation consistently
 explained the geographic variation in the extent of herbivory to Q.
 garryana, while latitude and winter temperatures, factors that are
 commonly associated with latitudinal gradients in the intensity of species
 interactions, did not. Our findings highlight the importance of local
 climates and functional traits in shaping biotic interactions and
 intraspecific variation in plant‐insect interactions across large spatial
 scales.
description: Loughnan&Williams_HerbivorydataInsect herbivory data on Quercus garryana collected from both a common garden and natural populations spanning the entire latitudinal range of this tree species. Data was collected for immature leaves early in the growing season and for mature leaves at the end of the season. Damage by chewing, skeletonizing, and mining insects was visually estimated and total damage calculated. In addition, tree height, diameter at breast height, and a population size category were also recorded. See the README file and description of Methods in the paper for metadata.Loughnan&Williams_TraitdataTrait data collected from leaves used for herbivory estimates for both early and late season sampling periods. Traits measured include specific leaf area and trichome density. See the README file for metadata.Loughnan&Williams_InsectdataInsect herbivore community data collected during the spring sampling period. A subsample of the insect community was collected from a 50 cm segment of Q. garryana branch. The number of unique species and number of individual insects were recorded. See the README file for metadata.