Tri-trophic consequences of herbivore diet breadth and plant resistance

生态学和进化生物学的一个基本目标是阐明决定草食动物消耗植物生物量的比例的因素。生态学家早就认识到，捕食者通过抑制食草动物的数量发挥作用。与此同时，进化生物学家的研究表明，草食物种对捕食者的脆弱性既取决于植物的营养质量，也取决于该草食动物饮食中包含的植物物种的多样性。这里资助的工作寻求整合这些独立但互补的研究领域。需要检验的最重要的假设是，植物的营养质量和食草动物的饮食广度共同决定了食草动物对捕食者的脆弱性。在这样做的过程中，植物质量和食草动物的饮食广度被预测，以确定捕食者在植物保护中的重要性，以及捕食者是否作为影响植物营养质量进化的自然选择的来源。这项拟议的工作使用了一个本地灌木及其相关昆虫群落的实验园来验证这一假设。营养质量不同的植物的遗传系将在实验处理中单独与草食动物一起种植，与草食动物和捕食者一起种植。这些植物将以两种草食动物中的一种为生：一种是只吃一种植物的蚜虫，另一种是以多种植物为食的蚜虫。因此，这项实验将测量捕食者对食草动物和植物的影响，以及这种影响是如何由食草动物的饮食广度和植物质量决定的。主要的更广泛的影响是在加州大学欧文植物园建立一个本地灌木公共花园的倡议，这是奥兰治县(人口300万)的两个以加州本土植物为特色的植物园之一。这次展览将为公众提供一个亲身实践的演示，展示决定草食动物营养质量的植物特性的变异，以及相关昆虫群落的自然历史信息。该花园还将成为本科生自主研究和教学机会的关键资源。

A fundamental goal of ecology and evolutionary biology is to elucidate the factors that determine what proportion of plant biomass is consumed by herbivores. Ecologists have long recognized that predators play a role by suppressing herbivore populations. At the same time, work by evolutionary biologists has shown that the vulnerability of an herbivore species to predators is determined by both plant nutritional quality and the diversity of plant species included in that herbivore's diet. The work funded here seeks to integrate these separate but complementary areas of research. The overarching hypothesis to be tested is that plant nutritional quality and herbivore diet breadth together determine an herbivore's vulnerability to predators. In so doing, plant quality and herbivore diet breadth are predicted to determine the importance of predators in plant protection, as well whether predators act as source of natural selection that influences the evolution of plant nutritional quality. The proposed work tests this hypothesis using an experimental garden of native shrubs and their associated insect community. Genetic lines of plants that vary in nutritional quality will be grown in experimental treatments with herbivores alone and with herbivores and predators together. These plants will be fed upon by one of two species of herbivore: an aphid that feeds only on one plant species or an aphid that feeds on a wide diversity of plants. This experiment will thus measure the effects of predators on herbivores and plants, and how such effects are determined by herbivore diet breadth and plant quality.The primary broader impact is an initiative to establish a public garden of native shrubs in the University of California-Irvine Arboretum, one of two botanical gardens featuring the native flora of California in Orange County (population 3 million). This display will provide the public with a hands-on demonstration of the variation in plant traits that determine its nutritional quality for herbivores, as well as information on the natural history of the associated insect community. The garden will also serve as a key resource for independent research and teaching opportunities for undergraduate students.