Chemical Ecology of Swallowtail Butterflies

这项研究的长期目标是发现植物之间的化学相似和差异如何影响植物与以植物为食的昆虫之间的联系。大多数以植物为食的昆虫都是专家，只在少数几种植物上取食和产卵。它们主要通过闻植物产生的特有气味，或者通过品尝植物组织或植物表面的化合物混合物，来发现和识别它们特定的食用植物。事实上，受到特殊种类昆虫攻击的植物物种通常共享一种或多种不寻常的化学化合物。这表明昆虫将新的植物物种添加到它们的食物中的能力是由于共享特定化合物的出现而促进的。由于燕尾蝶的分类和幼虫食物植物特别为人所知，所以本研究使用燕尾蝶(蝶科)作为模型系统。在接下来的三年里，PI们计划集中研究黑燕尾(Papilio Polyxes)，并确定为什么这种物种的雌性几乎从不在胡萝卜科(Apiaceae)以外的植物上产卵，但却接受这个科内广泛不同的物种。至少在一定程度上，雌性通过检测脚上带有味觉感受器的刺激性化合物和触角上的气味感受器来识别产卵植物。其中几种刺激性化合物已经被鉴定出来。PI将完成对三种常见寄主物种--胡萝卜、野生防风草和有毒铁杉--黑燕的这些兴奋剂的鉴定。然后，PI将确定兴奋剂的混合物是否具有共同的化合物，或者是否每种植物都被一组不同的兴奋剂化合物识别。在三种食用植物物种中，个体黑燕雌性的偏好将与对刺激物提取物的偏好进行比较，以确定这些偏好是否是不同物种之间寄主偏好的主要原因。PI将测量个体雌性喜好的变化，并抚养她们的后代，这样PI就可以比较她们雌性后代的相应偏好。这些实验将告诉我们，女性之间的差异是否至少部分是由于对化学物质反应的遗传差异造成的。尽管最近取得了进展，主要是在欧洲和日本，但令人惊讶的是，人们对昆虫识别寄主植物的化学混合物知之甚少，更不用说相关感觉机制背后的遗传学了。这项研究应该有助于明智地部署化学成分已被基因工程改造的新作物品种所需的基础知识。

The long-term goal of this research is to discover how chemicalsimilarities and differences among plants have influenced associationsbetween plants and the insects that feed on them. Most plant-feedinginsects are specialists, feeding and laying their eggs on only a few plantspecies. They find and identify their particular food plants largely bysmelling characteristic odors produced by the plants or by tastingcharacteristic mixtures of chemical compounds in the plant tissues or onthe plant surfaces. Indeed, plant species that are attacked by aparticular species of insect typically share one or more kinds of unusualchemical compounds. This suggests that the ability of insects to add newplant species to their diet is facilitated by the shared occurrence ofparticular compounds. The swallowtail butterflies (family Papilionidae) are used as amodel system in this research because their classification and larval foodplants are especially well known. During the next three years, the PIs plan toconcentrate on the black swallowtail (Papilio polyxenes) and to determinewhy females of this species almost never lay their eggs on plants outsidethe carrot family (Apiaceae) and yet accept a wide range of differentspecies within this family. At least in part, females identify plants onwhich to lay their eggs by detecting stimulant compounds with tastereceptors on their feet and by odor receptors in their antennae. Severalof these stimulant compounds have already been identified. The PIs willcomplete the identification of these stimulants for the black swallowtailin three common host species, namely carrot, wild parsnip, and poisonhemlock. The PIs will then determine whether the mixtures of stimulants sharecompounds in common or whether each plant is recognized by a different setof stimulant compounds. Preferences of individual black swallowtailfemales among the three food-plant species will be compared withpreferences for stimulant extracts to determine whether these are primarilyresponsible for host preference among different species. The PIs will measurevariation in the preferences of individual females and raise their progenyso that the PIs can compare the corresponding preferences of their femaleoffspring. These experiments will tell us whether variation among femalesresults, at least in part, from inherited differences in responses tochemical cues. Despite recent progress, mostly in Europe and Japan, remarkablylittle is known of the chemical mixtures by which insects recognize theirhost plants, let alone of the genetics underlying the relevant sensorymechanisms. This research should contribute to the basic knowledgerequired for the wise deployment of new crop varieties whose chemistry hasbeen modified by genetic engineering.