The Functional Significance of Variation in the Production of Extrafloral Nectaries by Aspen

花外蜜腺(EFN)是一种位于许多植物叶片和茎上的分泌蜜腺。它们可以作为一种植物防御形式，吸引以花蜜为食并以草食动物为食的昆虫。研究人员将使用现场实验来检验EFN在一种常见的北美树种--颤杨--中的防御功能。杨树叶片上EFN的发生有自然变异，这可能会导致杨树的防御水平不同。利用EFN表达的这种变化，这项研究将研究EFN在吸引蛇形白杨潜叶蛾天敌方面的作用。蛇形白杨潜叶蛾是一种草食动物，目前在阿拉斯加大部分地区严重侵袭白杨。蚂蚁和寄生蜂都可能是矿工的重要捕食者。然而，这些物种可能较少能够获得高叶与低叶，这可能会减少EFN在树木生长过程中的好处。这项研究将测试EFN的益处是否与身高有关。此外，研究人员还将测试这样一种假设，即杨树采叶虫避免在有EFN的树叶上产卵，因为它的后代面临更大的死亡风险。更广泛的影响：这项研究将有助于我们理解植物防御和昆虫-植物相互作用的进化。此外，它还将有助于更好地了解山杨这一分布广泛、具有生态和经济意义的树种的生态相互作用和防御特性。该项目将为阿拉斯加大学的两名研究生和许多本科生提供教育机会，其中包括通过国家科学基金会赞助的阿拉斯加原住民科学与工程计划招募的阿拉斯加原住民。此外，调查人员将创建一个互动网站，旨在让K-12年级的学生参与杨树生态研究。

Extrafloral nectaries (EFNs) are nectar-secreting glands located on the leaves and stems of many plant species. They can serve as a form of plant defense, by attracting insects that feed on the nectar and prey on herbivores. The investigators will use field experiments to examine the defensive function of EFNs in a common North American tree species, quaking aspen. Aspen have natural variation in the occurrence of EFNs on leaves, and this may result in differing levels of defense for aspen trees. Using this variation in EFN expression, the study will examine the role of EFNs in attracting natural enemies of the serpentine aspen leaf miner, an herbivore that currently heavily infests aspen throughout much of Alaska. Both ants and parasitic wasps are likely to be important predators on the miner. However, these species may be less able to access high versus low foliage and this could reduce the benefit of EFNs as trees grow. The study will test whether the benefits of EFNs are height-dependent. In addition, the investigators will test the hypothesis that the aspen leaf miner avoids laying eggs on leaves with EFNs, where its offspring face a greater risk of mortality. Broader Impacts: The study will contribute to our understanding of the evolution of plant defense and insect-plant interactions. In addition, it will provide a better understanding of the ecological interactions and defensive traits of quaking aspen, a widespread, ecologically and economically important tree species. The project will provide educational opportunities for two graduate students and many undergraduates at the University of Alaska, including Native Alaskans recruited through the National Science Foundation-sponsored Alaska Native Science and Engineering Program. In addition, the investigators will produce an interactive website designed to involve K-12 students in aspen ecology.