Data from: Global patterns of leaf defenses in oak species

Plant defensive traits drive patterns of herbivory and herbivore diversity among plant species. Over the past 30 years, several prominent hypotheses have predicted the association of plant defenses with particular abiotic environments or geographic regions. We used a strongly supported phylogeny of oaks to test whether defensive traits of 56 oak species are associated with particular components of their climatic niche. Climate predicted both the chemical leaf defenses and the physical leaf defenses of oaks, whether analyzed separately or in combination. Oak leaf defenses were higher at lower latitudes, and this latitudinal gradient could be explained entirely by climate. Using phylogenetic regression methods, we found that plant defenses tended to be greater in oak species that occur in regions with low temperature seasonality, mild winters, and low minimum precipitation, and that plant defenses may track the abiotic environment slowly over macroevolutionary time. The pattern of association we observed between oak leaf traits and abiotic environments was consistent with a combination of a seasonality gradient, which may relate to different herbivore pressures, and the resource availability hypothesis, which posits that herbivores exert greater selection on plants in resource-limited abiotic environments.

植物防御性状驱动不同植物物种间的植食作用模式与植食者多样性格局。过去30年间，多项具有影响力的假说已预测植物防御与特定非生物环境或地理区域存在关联。我们依托一套得到强力支持的栎树系统发育（phylogeny），检验了56种栎树的防御性状是否与其气候生态位（climatic niche）的特定组分相关联。无论单独分析还是联合分析，气候均可预测栎树的叶片化学防御（chemical leaf defenses）与叶片物理防御（physical leaf defenses）水平。栎树的叶片防御性状在低纬度地区更为显著，这一纬度梯度完全可由气候因素解释。通过系统发育回归（phylogenetic regression）分析方法，我们发现：分布于温度季节性低、冬季温和且最低降水量较少区域的栎树物种，其防御性状往往更强；且在宏演化（macroevolution）时间尺度上，植物防御性状可能缓慢追踪非生物环境的变化。我们观测到的栎树叶性状与非生物环境之间的关联模式，与两类假说的组合相符：一类是季节性梯度假说，该梯度可能与不同的植食者压力相关；另一类是资源可用性（resource availability）假说，该假说提出，在资源受限的非生物环境中，植食者会对植物施加更强的选择压。