INRAE, Univ. Bordeaux, BIOGECO, Cestas, France.
Misión Biológica de Galicia (MBG-CSIC), Pontevedra, Galicia, Spain.
Ann Bot. 2020 Oct 6;126(5):865-872. doi: 10.1093/aob/mcaa101.
Highly controlled experiments document that plant genetic diversity and relatedness can shape herbivore communities and patterns of herbivory. Evidence from the field is, however, scarce and inconsistent. We assessed whether a genetic signal underlying herbivory can be detected in oak woodlands when accounting for variation at smaller (within-tree) and larger (among-stand) scales.
We tested relationships between tree genetic relatedness, leaf chemical defences and insect herbivory for different canopy layers in 240 trees from 15 pedunculate oak (Quercus robur) forest stands. We partitioned sources of variability in herbivory and defences among stands, individuals and branches.
Leaf defences, insect herbivory and their relationship differed systematically between the upper and the lower tree canopy. When accounting for this canopy effect, the variation explained by tree genetic relatedness rose from 2.8 to 34.1 % for herbivory and from 7.1 to 13.8 % for leaf defences. The effect was driven by markedly stronger relationships in the upper canopy.
Our findings illustrate that considerable effects of the host plant genotype on levels of leaf chemical defences and associated insect herbivory can be detected in natural tree populations when within-individual variation is properly accounted for.
高度受控的实验证明，植物遗传多样性和相关性可以塑造食草动物群落和食草模式。然而，来自野外的证据却很少且不一致。我们评估了当考虑到更小（树内）和更大（林分间）尺度的变异时，食草性背后的遗传信号是否可以在橡树林中被检测到。
我们在 15 个欧洲山毛榉（Quercus robur）林分的 240 棵树中，针对不同的树冠层，测试了树木遗传相关性、叶片化学防御和昆虫食草性之间的关系。我们将食草性和防御性的变异性在林分、个体和树枝之间进行了划分。
叶片防御、昆虫食草性及其关系在树冠的上层和下层之间存在系统差异。当考虑到这种树冠效应时，由树木遗传相关性解释的变异从食草性的 2.8%上升到 34.1%，从叶片防御的 7.1%上升到 13.8%。这种效应是由上层树冠中明显更强的关系驱动的。
我们的研究结果表明，当适当考虑个体内变异时，在自然树木种群中，可以检测到宿主植物基因型对叶片化学防御和相关昆虫食草性水平的相当大的影响。
