Plant Secondary Metabolites as Mediators of Trophic Interactions in a Tropical Forest Community

对于陆地生态学家来说，量化和比较植物资源和消费者对生态群落的影响一直是困难的，但这是理解自然和管理的生态系统是如何结构以及它们如何应对干扰的重要组成部分。蚂蚁植物Piper cenocladum及其相关节肢动物一直是检验热带雨林自上而下和自下而上操纵效果的有用系统。拟议的实验将直接比较植物次生代谢物(酰胺)在调节草食方面的重要性与蚂蚁的作用。这些实验还将解决有关这些次生代谢物如何调节四个营养水平之间的相互作用的具体问题。将进行田间和荫棚实验，以检验几个假说。还将操纵捕食者和资源，并检查植物化学、植物生物量、食草动物数量和上层营养层生物量的变化。将进行食草动物摄食实验，以进一步研究酰胺类对食草动物的影响。这项研究是朝着清楚了解在该模式系统中观察到的营养级联迈出的重要一步。它将测试“绿色沙漠”模型，该模型表明植物次生化合物在塑造群落方面很重要，因为大多数植物不是食草动物可用的资源。它还将阐明资源可获得性和植物化学在改变营养级联中的作用。这项研究解决的更大的问题与当前关于资源可获得性和化学防御的理论有关，关于调节食草动物种群的因素的相对重要性的争议，以及蚂蚁-植物互惠关系的研究进展。这些结果将改进对当前理论的评估，并更好地为保护生物学和生物防治领域的实际决策提供参考。

0074806DyerQuantifying and comparing the impacts of plant resources and consumers on ecological communities has been difficult for terrestrial ecologists, but it is an important component of understanding how natural and managed ecosystems are structured and how they respond to perturbations. The ant-plant, Piper cenocladum, and its associated arthropods have been a useful system for examining the effects of top-down and bottom-up manipulations in a tropical rain forest. The proposed experiments will directly compare the importance of plant secondary metabolites (amides) in regulating herbivory versus the role of ants. The experiments will also address specific questions about how these secondary metabolites mediate interactions between the four trophic levels. Field and shade house experiments will be conducted to test several hypotheses. Predators and resources will also be manipulated and changes in plant chemistry, plant biomass, herbivore numbers, and biomass of upper trophic levels will be examined. Herbivore feeding experiments will be conducted to further examine the effects of amides on herbivores. This research is an important step towards gaining an clear understanding of the trophic cascades observed in this model system. It will test the "green desert" model, which suggests that plant secondary compounds are important in shaping communities, because most plants are not usable resources for herbivores. It will also shed light on the roles of resource availability and plant chemistry in modifying trophic cascades. The larger questions addressed by this research are relevant to current theories about resource availability and chemical defense, controversies about the relative importance of factors that regulate herbivore populations, and advances in studies of ant-plant mutualisms. The results will allow an improved assessment of current theory and better inform practical decisions in the areas of conservation biology and biological control.