Department of Natural Resources, Institute of Plant Sciences, Agricultural Research Organization - The Volcani Center, P.O. Box 6, 50250, Bet Dagan, Israel.
Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, 76100, Rehovot, Israel.
J Chem Ecol. 2020 Jan;46(1):99-113. doi: 10.1007/s10886-019-01124-x. Epub 2019 Dec 16.
Goat herding is an important tool in the ecologically sound management of Mediterranean shrublands and woodlands, although effective levels of woody biomass removal by the goats is neither guaranteed nor easy to predict. Preliminary observations indicated that one reason for this may be poor understanding of plant-herbivore interactions that operate intraspecifically at the local spatial scale. We asked, whether goats show intraspecific preferences among neighboring plants when foraging a small local population of Pistacia lentiscus, a dominant tall shrub. First, we characterized and quantified the profile of stored and emitted volatile organic compounds (VOCs) and the PEG-binding capacity of tannins (a proxy for protein binding capacity) in the foliage of P. lentiscus shrubs, sampled within an area of 0.9 ha. We then tested goat preference between pairs of these shrubs that differed in chemical composition. Almost all sampled P. lentiscus shrubs were allocated to one of two distinct VOC chemotypes: one dominated by germacrene D and limonene (designated chemotype L) and the other by germacrene D and α-pinene (chemotype P). In contrast, continuous moderate variability was found in the binding capacity of tannins in the foliage. Goats showed preference for shrubs of chemotype L over those of chemotype P, and their preference was negatively correlated with the binding capacity of tannins. Possible influences of VOCs on goat preference that may explain the observed patterns are discussed in the light of possible context-dependent interpretation of plant VOC signals by large mammalian herbivores.
放牧是地中海灌木和林地生态合理管理的重要工具，尽管山羊对木质生物质的有效去除水平既无法保证也不容易预测。初步观察表明，造成这种情况的一个原因可能是对在当地空间尺度上种内发生的植物-食草动物相互作用理解不足。我们询问了在觅食一小片本地生长的乳香黄连木（一种占优势的高大灌木）时，山羊是否会在相邻植物中表现出种内偏好。首先，我们对在 0.9 公顷的范围内采样的乳香黄连木灌木叶片中的储存和排放的挥发性有机化合物 (VOC) 谱以及单宁的 PEG 结合能力（蛋白质结合能力的代表）进行了特征描述和量化。然后，我们测试了这些在化学成分上存在差异的成对灌木之间的山羊偏好性。几乎所有采样的乳香黄连木灌木都被分配到两种截然不同的 VOC 化学型之一：一种以大根香叶烯 D 和柠檬烯为主（指定为 L 化学型），另一种以大根香叶烯 D 和α-蒎烯为主（P 化学型）。相比之下，叶片中单宁的结合能力存在连续的中度可变性。山羊对 L 化学型灌木的偏好超过 P 化学型灌木，并且它们的偏好与单宁的结合能力呈负相关。根据大型哺乳动物食草动物对植物 VOC 信号的可能依赖于上下文的解释，讨论了 VOC 对山羊偏好的可能影响，这些影响可能解释了观察到的模式。
