Dissertation Research: Physiological/Biochemical Tradeoffs with Host Specialization: Ecological Implications for Generalist and Specialist Saturniids (Callosamia spp)

很少有食草性昆虫利用白玉兰作为寄主植物，其中一种是白玉兰。然而，亲缘关系密切的物种在这种植物上100%死亡。初步的植物化学研究表明，死亡是由于至少两种杀虫化合物，厚朴酚和联苯醚。本研究将通过比较木兰花的解毒机制和两种不能耐受木兰花化学物质的同系物来研究木兰花对木兰花的生理生化适应。体外和体内实验将用于鉴定酶解毒系统。此外，由于这三个Callsamia物种最近似乎出现了分歧，在寄主使用上有一些重叠，因此将测试在消化效率和解毒酶活性方面的可能权衡，这可能有利于该属的寄主植物专业化。具体地说，1)专家的消化效率高于多面手的预测，以及2)多面手的广谱底物专一性解毒活性的水平更高的预测，或者3)比专家更高的诱导能力的预测将被测试。随着对安全隐翅虫用于处理寄主毒素的特定解毒机制的详细描述，有可能提出关于与寄主专化相关的生化权衡的更好的假说。

Few insect herbivores utilize Magnolia virginiana (sweetbay) as a hostplant, one being the sweetbay silkmoth, Callosamia securifera (Saturniidae). However, closely related species suffer 100% mortality on this plant. Preliminary phytochemical work indicates that mortality is due to at least two insecticidal compounds, magnolol and biphenyl ether. This study will characterize physiological/biochemical adaptations of C. securifera to Magnolia by comparing its detoxification mechanisms with those of two congeners unable to tolerate this host's chemicals. In vitro and in vivo experiments will be used to identify enzymatic detoxification systems. In addition, because the three Callosamia species appear to have recently diverged and have some overlap in host use, possible tradeoffs in digestive efficiency and detoxification enzyme activity that may have favored hostplant specialization in the genus will be tested. Specifically, predictions that 1) specialists have higher digestive efficiency than generalists and 2) generalists have higher levels or 3) higher inducibility of broad substrate-specificity detoxification activity than specialists will be tested. With the detailed characterization of specific detoxification mechanisms used by C. securifera to cope with toxins in its host, it may be possible to formulate better hypotheses concerning biochemical tradeoffs associated with host specialization.