Adler Lynn S, Schmitt Johanna, Bowers M Deane
Department of Ecology and Evolutionary Biology, Brown University, Box G-W, 02912, Providence, RI, USA.
University Museum, Department of Environmental, Population and Organismic Biology, University of Colorado, Campus Box 334, 80309, Boulder, CO, USA.
Oecologia. 1995 Jan;101(1):75-85. doi: 10.1007/BF00328903.
To examine genetic variation in defensive chemistry within and between natural populations of Plantago lanceolata, we performed a greenhouse experiment using clonal replicates of 15 genotypes from each of two populations, from a mowed lawn and an abandoned hayfield. Replicates of each genotype were harvested for determinations of aboveground biomass and leaf chemical content either at the beginning of the experiment (initial controls), after exposure to herbivory by larvae of Junonia coenia, a specialist on P. lanceolata (herbivory treatment), or at the end of the experiment without exposure to herbivory (final controls). Allocation to the iridoid glycosides aucubin and catalpol and the phenylpropanoid glycoside verbascoside displayed significant genetic variation within and between populations, and differed with leaf age. Significant genotypextreatment interactions indicated genetic variation in response of leaf chemistry to the treatments. There was no evidence for a cost of allocation to chemical defense: genetic correlations within and between chemical pathways and between defensive chemicals and aboveground growth were positive or nonsignificant. Although iridoid glycosides are known to be qualitative feeding stimulants for J. coenia, multiple regression of larval survivorship on leaf chemical content and shoot biomass indicated that larvae had lower survivorship on P. lanceolata ge-notypes with higher concentrations of aucubin in the leaves. Larval survivorship was unaffected by levels of catalpol and verbascoside. Thus, although specialist herbivores may respond to defensive chemicals as qualitative feeding stimulants, they do not necessarily have higher fitness on plant genotypes containing higher concentrations of these chemicals.
为了研究披针叶车前自然种群内部和种群之间防御化学物质的遗传变异，我们进行了一项温室实验，使用了来自割草草坪和废弃干草地两个种群中各15个基因型的克隆复制品。在实验开始时（初始对照）、暴露于专食披针叶车前的艳婀珍蝶幼虫的取食后（取食处理）或在未暴露于取食的实验结束时（最终对照），采集每个基因型的复制品以测定地上生物量和叶片化学物质含量。环烯醚萜苷桃叶珊瑚苷和梓醇以及苯丙素苷毛蕊花糖苷的分配在种群内部和种群之间均表现出显著的遗传变异，并且随叶龄而不同。显著的基因型×处理交互作用表明叶片化学物质对处理的反应存在遗传变异。没有证据表明化学防御的分配存在代价：化学途径内部和之间以及防御化学物质与地上生长之间的遗传相关性为正或不显著。尽管已知环烯醚萜苷是艳婀珍蝶的定性取食刺激物，但幼虫存活率对叶片化学物质含量和地上生物量的多元回归表明，在叶片中桃叶珊瑚苷浓度较高的披针叶车前基因型上，幼虫的存活率较低。幼虫存活率不受梓醇和毛蕊花糖苷水平的影响。因此，尽管专食性食草动物可能会将防御化学物质作为定性取食刺激物做出反应，但它们在含有较高浓度这些化学物质的植物基因型上不一定具有更高的适合度。
