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性和差异性如何影响植物和以它们为食的昆虫之间的联系。大多数植食昆虫都是专门性的，它们只以少数几种植物为食并产卵。它们主要通过嗅闻植物产生的特有气味或品尝植物组织或植物表面的化学化合物的特有混合物来发现和识别特定的食物植物。事实上，受到特定种类昆虫攻击的植物物种通常具有一种或多种不寻常的化合物。这表明，昆虫在其饮食中添加新植物物种的能力是由共同出现的特定化合物促进的。本研究选用凤蝶科的燕尾蝶作为模型系统，因为其分类和幼虫的食性植物是已知的。在接下来的三年里，pi计划集中研究黑燕尾（Papilio polyxenes），并确定为什么这个物种的雌性几乎从不在胡萝卜科（蜂科）以外的植物上产卵，却接受这个科中各种不同的物种。至少在某种程度上，雌性通过脚上的味觉感受器和触角上的气味感受器来探测刺激性化合物，从而识别出可以产卵的植物。其中几种刺激性化合物已经被鉴定出来。pi将在三种常见的寄主物种，即胡萝卜，野生防风草和毒铁杉中完成这些刺激物的鉴定。然后，pi将确定兴奋剂混合物是否具有共同的化合物，或者每种植物是否被一组不同的兴奋剂化合物识别。雌性黑燕尾个体对三种食用植物的偏好将与对兴奋剂提取物的偏好进行比较，以确定它们是否主要负责不同物种之间的宿主偏好。pi将测量个体雌性偏好的变化，并培养它们的后代，以便pi可以比较其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，至少在一定程度上，是否源于对化学物质反应的遗传差异。尽管最近取得了进展，主要是在欧洲和日本，但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。这一研究成果将为合理配置化学成分经过基因工程修饰的作物新品种提供基础知识。

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.