Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg, Denmark.
J Chem Ecol. 2010 Dec;36(12):1335-45. doi: 10.1007/s10886-010-9880-5. Epub 2010 Nov 17.
In an attempt to identify chemical signals governing the general flower and silique feeding behavior of larvae of the orange tip butterfly, Anthocharis cardamines (L.), we investigated feeding behavior and chemistry of two major host plants: Cardamine pratensis L. and Alliaria petiolata (Bieb.) Cavara & Grande (garlic mustard). Larvae reportedly feed mainly on flowers and siliques rather than leaves in nature, and did so when observed on the original host plants. Behavioral experiments, using detached A. petiolata branches, however, showed that larvae readily accepted leaves and only the final instar showed a tendency for directed movement towards floral parts. To search for semiochemicals that control plant part preference and to assess possible nutritional consequences of floral parts feeding, we determined glucosinolate profiles and total nitrogen levels of floral parts and leaves. There was only moderate difference between glucosinolate profiles of leaves and floral parts within each of two host plant species. In contrast, the profiles of floral parts differed significantly between them. A. petiolata was dominated by 2-propenyl glucosinolate, while C. pratensis was dominated by aromatic glucosinolates and branched aliphatic glucosinolates, with considerable variation among populations. Nitrogen levels tended to be higher in floral parts than in leaves in A. petiolata, but not in C. pratensis, so floral feeding could not generally be attributed to higher N content. With the exception of a tendency of last instar larvae (L5) to move to the apex and ingest flowers and upper stem, we did not find either a plant chemistry basis or larval acceptance/rejection behavior that could explain the usual feeding of floral parts by orange tip larvae of all instars. However, by artificial manipulation of vertical larval position on host plants, we found that the frequency of leaf vs. flower feeding during 24 hr depended significantly on the initial larval position. Hence, we suggest that the placement of eggs on floral parts by ovipositing female butterflies is a major explanation of orange tip feeding habits previously known from field observations.
为了确定控制橙色斑点蝶幼虫一般花卉和豆荚取食行为的化学信号，我们研究了两种主要寄主植物：菥蓂（Cardamine pratensis L.）和大蒜芥（Alliaria petiolata (Bieb.) Cavara & Grande）的取食行为和化学特性。据报道，幼虫在自然界中主要以花和豆荚为食，而不是叶子，在观察到的原始寄主植物上也是如此。然而，使用分离的大蒜芥枝条进行的行为实验表明，幼虫很容易接受叶子，只有最后一龄幼虫有向花部定向移动的趋势。为了寻找控制植物部位偏好的半化学物质，并评估花卉部分取食的可能营养后果，我们测定了花部和叶片的硫代葡萄糖苷图谱和总氮水平。在两种寄主植物的每一种中，叶片和花部的硫代葡萄糖苷图谱之间只有中等差异。相比之下，花部的图谱在它们之间有显著的差异。大蒜芥主要由 2-丙烯基硫代葡萄糖苷组成，而菥蓂则以芳香硫代葡萄糖苷和支链脂肪硫代葡萄糖苷为主，不同种群之间存在很大差异。氮水平在大蒜芥的花部往往高于叶片，但在菥蓂中则不然，因此花卉取食一般不能归因于较高的氮含量。除了最后一龄幼虫（L5）有向顶端移动并摄取花朵和上部茎的趋势外，我们没有发现可以解释橙色斑点幼虫各龄期通常取食花朵的植物化学基础或幼虫接受/拒绝行为。然而，通过对寄主植物上垂直幼虫位置的人工操作，我们发现 24 小时内叶片与花朵取食的频率显著取决于幼虫的初始位置。因此，我们认为，产卵的雌性蝴蝶将卵产在花朵上，这是橙色斑点蝴蝶取食习性的一个主要解释，这是以前从野外观察中得知的。
