Effects of 3-Trophic-Level Interactions on Sex Ratios of an Herbivore and Parasitoid

本文研究了十字花科植物主要食草动物小菜蛾（Pluetella xylostella）及其主要寄生蜂Diadegma insulare之间的三营养水平相互作用。蛾类和寄生蜂的性别比和种群大小与食用植物的差异相关；营养水平可能对种群规模的调节以及这些昆虫物种与群落其他组成部分之间相互作用的动态变化产生重大影响。利用野生十字花科植物和栽培十字花科植物，探讨草食植物和拟寄生物的性别比例变化。从野生和栽培生境中选择物种将允许对大量植物特性进行扫描，从氮、防御化学和形态等因素的个体差异，到斑块大小和密度的种群差异。该研究的主要目的是确定影响种群和社区环境中飞蛾和黄蜂性别比例的因素。第二个目标是比较野生十字花科植物与栽培十字花科植物之间的相互作用。总之，这些不同的系统涵盖了一系列的社区情况，从高密度的农业环境，通常研究人口相互作用和性别比变化，到低密度的零散社区，这些相互作用和昆虫行为可能在其中进化。

Three-trophic-level interactions among cruciferous plants, one of their major herbivores, the diamondback moth Pluetella xylostella and its major parasitoid Diadegma insulare will be studied. Sex ratios and population sizes of both the moth and the parasitoid are correlated with differences in food plants; and the trophic levels are likely to have major effects on the regulation of population size and the dynamics of interactions between these insect species and other components of the community. The variations in the sex ratios of the herbivore and its parasitoid, using both wild and cultivated crucifers will be explored. Selection of species from both wild and cultivated habitats will allow the scanning of a large array of plant properties, from individual variation in such factors as nitrogen, defensive chemistry and morphology, up to population variation in patch size and density. The primary goal of the research is to identify factors affecting both moth and wasp sex ratios within population and community contexts. The secondary goal is to compare these interactions on wild vs. cultivated crucifers. Together, these different systems cover an array of community situations from the high density, agricultural environments in which population interactions and sex ratio variation are usually studied, to the low density, patchy communities in which these interactions and insect behaviors probably evolved.