Chemical Ecology of Resin Secretion in Dalechampia (Euphorbiacea): Radical Evolutionary Shifts in the Functions of Triterpenses?

植物次生化学物质在植物与它们的互助者和拮抗者之间的许多关系中起调节作用。这些动植物关系的数量和特殊性造就了热带地区的大部分生物多样性。植物通常使用次生化合物来防御食草动物或作为互助者的引诱剂。化学上相似的化合物在相关植物中可能具有不同的功能。这项拟议的研究将通过检验这样一种假设来阐明动植物相互作用的模型系统，即萜类树脂在原始物种的叶片、托叶和花小苞片中起到防御草食动物和/或病原体的作用，而在授粉中没有作用。根据这一假说，原始的棒状花柱属物种应该用树脂来保护花和叶子免受食草动物的侵袭，同时为传粉者提供一些其他奖励，比如花粉或香水。为了测试这些想法，拟议的项目将：i)通过在天然草食动物饲养试验中使用树脂提取物，确定无腺和含腺物种的萜类树脂是否阻止食草动物；ii)通过测试微生物生物检测中的提取物，确定萜类树脂是否抑制微生物；Iii)通过对产生的化合物进行调查和分析，研究花卉树脂和营养树脂之间的化学关系；以及iv)观察原始无腺的达勒坎皮物种的授粉和草食情况。这项研究的信息将使我们更深入地了解动植物相互作用的化学基础，这种相互作用是如何演变的，以及新的互惠关系是如何产生的。

Plant secondary chemicals mediate many relationships between plants and their mutualists and antagonists. The number and specificity of these plant-animal relationships generates much of the biodiversity of the tropics. Plants commonly use secondary compounds as defense against herbivores or as attractants for mutualists. Chemically similar compounds may serve different functions in related plants. The proposed research will elucidate a model system of plant-animal interactions by testing the hypothesis that terpenoid resins, which function as floral rewards for bees in most species of Dalechampia, function in the leaves, stipules, and floral bractlets of primitive species as a defense against herbivores and/or pathogens, and play no role in pollination. Primitive species of Rhopalostylis, according to the hypothesis, should defend flowers and leaves against herbivores with resin, while offering pollinators some other reward, such as pollen or fragrances. To test these ideas the proposed project will i) establish whether or not the terpenoid resins of glandless and gland-bearing species deter herbivores, by using resin extracts in feeding trials with natural herbivores; ii) establish whether or not the terpenoid resins inhibit microorganisms, by testing extracts in bioassays with microorganisms; iii) investigate the chemical relationships between the floral and vegetative resins by surveying and analyzing the compounds produced; and iv) make observations on the pollination of, and herbivory on, primitively glandless species of Dalechampia. Information from this study will give us greater insight into the chemical basis of plant-animal interactions, how such interactions evolve, and how novel mutualisms arise.