Leaf drop affects herbivory in oaks

Leaf phenology is important to herbivores, but the timing and extent of leaf drop has not played an important role in our understanding of herbivore interactions with deciduous plants. Using phylogenetic general least squares regression, we compared the phenology of leaves of 55 oak species in a common garden with the abundance of leaf miners on those trees. Mine abundance was highest on trees with an intermediate leaf retention index, i.e. trees that lost most, but not all, of their leaves for 2–3 months. The leaves of more evergreen species were more heavily sclerotized, and sclerotized leaves accumulated fewer mines in the summer. Leaves of more deciduous species also accumulated fewer mines in the summer, and this was consistent with the idea that trees reduce overwintering herbivores by shedding leaves. Trees with a later leaf set and slower leaf maturation accumulated fewer herbivores. We propose that both leaf drop and early leaf phenology strongly affect herbivore abundance and ...叶片物候（leaf phenology）对植食性昆虫（herbivores）具有重要生态意义，但落叶的时间与程度，在我们理解植食性昆虫与落叶植物（deciduous plants）的互作关系中，却未得到足够的关注。本研究采用系统发育广义最小二乘回归（phylogenetic general least squares regression）方法，对比了同质园（common garden）中55种栎树的叶片物候与对应植株上潜叶昆虫（leaf miners）的发生量。结果显示，潜叶昆虫的发生量在叶片保留指数（leaf retention index）处于中等水平的栎树上达到峰值：这类树木会脱落大部分而非全部叶片，且落叶时长为2至3个月。常绿性更强的树种，其叶片硬化程度更高，这类硬叶（sclerotized leaves）在夏季的潜叶虫蛀痕数量更少。落叶性更强的树种，夏季的潜叶虫蛀痕数量同样更少，这一结果与“树木通过脱落叶片以减少越冬植食性昆虫种群”的假说一致。展叶期（leaf set）更晚、叶片成熟速率（leaf maturation）更慢的树木，其植食性昆虫种群数量也更少。我们提出，叶片脱落与早期叶片物候均会显著影响植食性昆虫的种群数量，且……