Dissertation Research: The Relative Roles of Host Quality and Enemy Free Space in Determining the Host Preferences of a Generalist Herbivore, Vanessa cardui

植物-昆虫相互作用研究中的一个核心问题是，为什么食草昆虫倾向于将它们的摄食限制在有限的宿主范围内。本研究的目的是通过比较多面手草食动物在几种可能的宿主上的表现，从宿主质量和天敌的攻击率两方面来解决专业化问题。初步调查表明，相对于其他可用的宿主，Vanessa cardui在其首选宿主上的生长较差，这表明在决定其宿主偏好方面，宿主质量相对而言不如其他生态因素重要。天敌在决定寄主偏好方面的潜在作用已被有力地阐明，但实验研究仍然相对缺乏。本文提出了天敌重要性的纬度梯度的可能性，并将通过比较不同地点卡杜氏弧菌的寄主偏好和天敌攻击率的变化来进行研究。本研究选择了一个多面手食草动物，以便在食草动物有足够的时间在多个维度上适应它的宿主之前，对食草动物在各种宿主上的表现进行清晰的观察。

A central question in the study of plant-insect interactions is why herbivorous insects tend to restrict their feeding to a limited range of hosts. The goal of the proposed research is to address this question of specialization by comparing a generalist herbivore's performance on several possible hosts in terms of both host quality and the rate of attack by natural enemies. Preliminary investigations have demonstrated that Vanessa cardui's growth is poor on its preferred host relative to other available hosts, suggesting that host quality is relatively less important than other ecological factors in determining its host preferences. The potential role of natural enemies in determining host preferences has been forcefully stated but remains relatively depauperate of experimental study. The possibility of a latitudinal gradient in importance of natural enemies is suggested and will be investigated by comparing variation in V. cardui's host preferences and the rate of attack by natural enemies in several sites. A generalist herbivore has been chosen for this study to obtain an unobscured view of the herbivore's performance on a variety of hosts before the herbivore has had significant time to adapt to its host in multiple dimensions.