Department of Entomology & Nematology, University of California , Davis, CA 95616, USA.
Department of Environmental and Biological Sciences, University of Eastern Finland, Yliopistonranta 8 , Kuopio 70211, Finland.
Proc Biol Sci. 2024 Sep;291(2031):20241513. doi: 10.1098/rspb.2024.1513. Epub 2024 Sep 18.
Herbivory is a major threat to virtually all plants, so adaptations to avoid herbivory will generally be selected. One potential adaptation is the ability to 'listen in' on the volatile cues emitted by plants that are experiencing herbivory and to then respond by ramping up defences. The nature of these volatile cues is poorly understood. Sagebrush () plants that were exposed to cues of experimentally damaged neighbours experienced less herbivory; this induction was most effective if emitter and receiver plants had similar volatile emission profiles, termed chemotypes. Previously, we observed that sagebrush populations that were in locations with high herbivory exhibited little diversity of volatiles compared to populations with low herbivory. Several hypotheses could produce this correlation. High risk of herbivory could have selected for individuals that converged on a common 'alarm cue' that all individuals would respond to. In this case, individuals of locally rare chemotypes that were less able to eavesdrop would experience more damage than common chemotypes when herbivores were abundant. Alternatively, low chemotypic diversity could allow higher levels of damage to plants. In this case, rare chemotypes would experience less damage than common chemotypes. We examined the chemotypes of sagebrush individuals from multiple sites and found that rare chemotypes experienced more damage than common chemotypes when herbivores were abundant. This pattern was seen among sites and among years with different densities of herbivores. This result is consistent with the hypothesis that herbivory selects for individuals that are effective communicators and shapes the communication system.
食草是几乎所有植物的主要威胁，因此避免食草的适应通常会被选择。一种潜在的适应是能够“监听”正在经历食草的植物发出的挥发性线索，然后通过加强防御来做出反应。这些挥发性线索的性质还不太清楚。暴露在实验性受损邻居线索下的鼠尾草植物受到的食草侵害较少；如果发射器和接收器植物具有相似的挥发性排放谱，即化学型，这种诱导作用最为有效。以前，我们观察到，与食草率低的种群相比，食草率高的种群的挥发性物质多样性很少。有几个假设可以产生这种相关性。高食草风险可能选择了那些趋同于共同“警报线索”的个体，所有个体都会对其做出反应。在这种情况下，当食草动物丰富时，本地稀有化学型的个体由于偷听能力较弱，比常见化学型的个体更容易受到更多的伤害。或者，低化学型多样性可能会导致植物受到更高水平的伤害。在这种情况下，稀有化学型的个体比常见化学型的个体受到的伤害更小。我们检查了来自多个地点的鼠尾草个体的化学型，发现当食草动物丰富时，稀有化学型比常见化学型受到的伤害更大。这种模式在不同地点和不同食草密度的年份中都存在。这一结果与这样一种假设一致，即食草动物选择了有效的沟通者，并塑造了沟通系统。
