Science. 1976 Jul 2;193(4247):24-9. doi: 10.1126/science.193.4247.24.
Optimal plant defense should incorporate any mechanisms that influence the feeding behavior of potential pests. From a diverse collection of examples suggesting that the defense of a plant may be improved in the company of specific neighbors, we discuss a framework of operational mechanisms that begin to clarify some aspects of the recognized influence of species diversity on herbivory. Neighbors serve as insectary plants for herbivore predators and parasites, and influence herbivore feeding behavior by repelling, masking, attracting, and decoying. Insectary plants lower the numerical response of herbivores by increasing the efficiency of their predators and parasites. Repellent plants primarily lower functional response by causing the predator to fail to locate or reject its normal prey. Attractant-decoy plants dilute herbivore impact by drawing off herbivores, either increasing or decreasing their numerical and functional response (or either). The concept of gene conservation guilds adds diversionary and delaying tactics to the adaptation-counteradaptation view of plant-herbivore coevolution. The useful life of a given gene for resistance may best be extended by mechanisms that disrupt genetic tracking (specialization) by herbivores. Some plants may remain inedible not because their chemistry or morphology represents an evolutionary impasse, but because they live in an environment that provides acceptable options of variable quality. Feeding environments that provide little or no choice promote specialization by forcing physiological adaptation. Conversely, the evolutionary momentum of specializing herbivores may be lowered by enhancing their susceptibility, either by selection against virulent individuals, or by decreasing the exposure frequency of susceptible genotypes. The latter mechanism of conserving susceptible individuals takes advantage of herbivore behavioral sensitivity to variable plant quality. Direct selection against virulent genotypes requires temporal cycling of the herbivore population between resistant and nonresistant hosts. Both events may occur within defense guilds that provide acceptable feeding options of similar but distinctive quality.
最优的植物防御策略应包含任何影响潜在害虫取食行为的机制。从大量的例子中可以看出，当与特定的邻居在一起时，植物的防御能力可能会得到提高。我们讨论了一个操作机制框架，该框架开始阐明物种多样性对食草性影响的一些方面。邻居是食草性动物的捕食者和寄生虫的滋生地，并通过驱赶、掩盖、吸引和诱捕来影响食草动物的取食行为。食草性动物的滋生地通过提高其捕食者和寄生虫的效率来降低食草动物的数量反应。驱避植物主要通过使捕食者无法定位或拒绝其正常猎物来降低功能反应。吸引-诱捕植物通过吸引食草动物来稀释食草动物的影响，从而增加或减少其数量和功能反应（或两者兼而有之）。基因保护 guilds 的概念为植物-食草动物协同进化的适应-反适应观点增加了转移和拖延策略。通过破坏食草动物的遗传跟踪（特化）的机制，可以延长抗性基因的有效寿命。一些植物可能仍然不可食用，不是因为它们的化学物质或形态代表了进化的僵局，而是因为它们生活在一个提供可接受的可变质量选择的环境中。提供很少或没有选择的取食环境通过迫使生理适应来促进特化。相反，通过选择对毒力个体不利，或通过降低易感基因型的暴露频率，可能会降低特化食草动物的进化动力。后一种保护易感个体的机制利用了食草动物对可变植物质量的行为敏感性。直接选择对毒力基因型的要求是食草动物种群在抗性和非抗性宿主之间进行时间循环。这两个事件都可能发生在提供相似但有区别质量的可接受取食选择的防御 guilds 中。
