PRF/J: The Consequences of Resource Availability and Plant Apparency on Patterns of Herbivory and Herbivore Defense in an Annual Tarweed, Hemizonia luzulaefolia

本论文将以菊科植物灯盏花的生态型为研究对象，考察与植物对食草动物的防御进化有关的两种理论的预测：资源可获得性假说和显性假说。资源可获得性假说预测，与适应高资源环境的植物相比，适应低资源环境的植物应该按比例分配更多的资源用于防御。将使用两种生态型(一种适应于资源贫乏的蛇纹石土壤，另一种适应于资源丰富的砂岩土壤)，在1)相互移栽花园实验中评估植物适合性，2)容器实验以检查潜在的生态生理机制)。羽扇在开花前产生非树脂的莲座状叶子，开花时产生树脂状的叶子(可能是对食草动物的防御)。此外，两个生态型在开花时间(春季和秋季)和产生树脂的数量上也不同。表现力假说预测，树脂生产的时间和数量的这种变化可归因于对食草动物的易感性的变化。这一想法将通过在季节期间多次将两种生态型的不同生长阶段放置在草原上并测量草食动物的损害来检验。预计这些实验产生的结果将为修正当前关于草食动物防御进化的理论提供经验基础。//

Ecotypes of Hemizonia Luzulaefolia (Asteraceae) will be used to examine predictions of two theories concerned with the evolution of plant defenses against herbivores: the resource availability and the apparency hypotheses. The resource availability hypothesis predicts that plants adapted to low- resource environments should allocate proportionally more resources to defense than plants adapted to high-resource environments. Two ecotypes of H.luzulaefolia (one adapted to resource-poor serpentine soil and one adapted to resource-rich sandstone soil) in 1) a reciprocal transplant garden experiment to assess this prediction in terms of plant fitness and 2) a container experiment to examine underlying eco-physiological mechanisms) will be used. H.luzulaefolia produces non-resinous rosette leaves prior to flowering and resinous leaves (presumably a defense against herbivores) when flowering is initiated. In addition, two ecotypes differ in flowering time (spring vs.fall) and in quantity of resins produced. The apparency hypothesis predicts that this variation in the timing and quantity of resin production is attributable to variation in vulnerability to herbivores. This idea will be tested by placing different growth stages of the two ecotypes into the grassland at several times during the season and measure herbivore damage. It is anticipated that results generated from these experiments will provide an empirical base for modifying current theory on the evolution of herbivore defense. //