Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853.
Department of Entomology, Cornell University, Ithaca, New York 14853.
Evolution. 2018 May;72(5):1020-1033. doi: 10.1111/evo.13451. Epub 2018 Mar 12.
To address the role of insect herbivores in adaptation of plant populations and the persistence of selection through succession, we manipulated herbivory in a long-term field experiment. We suppressed insects in half of 16 plots over nine years and examined the genotypic structure and chemical defense of common dandelion (Taraxacum officinale), a naturally colonizing perennial apomictic plant. Insect suppression doubled dandelion abundance in the first few years, but had negligible effects thereafter. Using microsatellite DNA markers, we genotyped >2500 plants and demonstrate that insect suppression altered the genotypic composition of plots in both sampling years. Phenotypic and genotypic estimates of defensive terpenes and phenolics from the field plots allowed us to infer phenotypic plasticity and the response of dandelion populations to insect-mediated natural selection. The effects of insect suppression on plant chemistry were, indeed, driven both by plasticity and plant genotypic identity. In particular, di-phenolic inositol esters were more abundant in plots exposed to herbivory (due to the genotypic composition of the plots) and were also induced in response to herbivory. This field experiment thus demonstrates evolutionary sorting of plant genotypes in response to insect herbivores that was in same direction as the plastic defensive response within genotypes.
为了研究昆虫食草动物在植物种群适应和选择通过演替持续中的作用，我们在一个长期的野外实验中操纵了食草动物的作用。我们在九年的时间里，在 16 个样地中的一半中抑制了昆虫的作用，并研究了普遍存在的归化多年生无性繁殖蒲公英（Taraxacum officinale）的基因型结构和化学防御。昆虫抑制在最初几年使蒲公英的数量增加了一倍，但此后几乎没有影响。使用微卫星 DNA 标记，我们对超过 2500 株植物进行了基因分型，并证明昆虫抑制改变了两个采样年份样地的基因型组成。来自野外样地的防御萜烯和酚类的表型和基因型估计值使我们能够推断蒲公英种群对昆虫介导的自然选择的表型可塑性和反应。昆虫抑制对植物化学的影响确实是由可塑性和植物基因型身份共同驱动的。具体而言，双酚肌醇酯在暴露于食草作用的样地中更为丰富（由于样地的基因型组成），并且也对食草作用产生了诱导。因此，这个野外实验证明了植物基因型对昆虫食草动物的进化分类，这与基因型内的防御性表型反应方向相同。
