The ecological effects of the keystone mutualism between sap-feeding insects have been evaluated from the individual to landscape scales, but these effects’ fine-scale variation has not been characterized well. Here, we tested a simple hypothesis that aphid-tending ants’ effect on plant herbivory should be stronger on small leaves, with a dataset that included 15,602 leaves of a widely distributed oak tree (Quercus wutaishansea). The results showed that, consistent with our prediction, aphid-tending ants’ anti-herbivory effect decreased with leaf size. However, further analysis showed that this pattern was significant only at the beginning (May) and end (September) of the growing season. These results show that there is considerable variation in ants’ anti-herbivory effect even within an individual tree. Given that small leaves often are younger and more valuable than larger ones, our study suggests that a plant’s biotic partners protect its more valuable parts better.

中文翻译：

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梯形相互作用的精细变化：趋于蚜虫的蚂蚁对小叶片显示出更强的抗草食作用

从个体到景观尺度都评估了树液喂养昆虫之间梯形共生的生态效应，但是这些效应的精细尺度变化并没有得到很好的表征。在这里，我们测试了一个简单的假设，即在小叶上趋于蚜虫的蚂蚁对植物食草的作用应更强，该数据集包含15602棵分布广泛的橡树（栎木五台山海）的叶子。）。结果表明，与我们的预测一致，趋于蚜虫的蚂蚁的防草食作用随叶片大小而降低。但是，进一步的分析表明，这种模式仅在生长季节的开始（5月）和结束（9月）才有意义。这些结果表明，即使在单个树中，蚂蚁的抗草食性效果也存在很大差异。考虑到小叶通常比大叶更年轻且更有价值，因此我们的研究表明，植物的生物伴侣可以更好地保护其更有价值的部分。