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

很少有昆虫食草动物利用白玉兰（甜湾）作为寄主植物，其中一种是甜湾蚕蛾，Callosamia securifera （Saturniidae）。然而，近缘种在这种植物上的死亡率为100%。初步的植物化学工作表明，死亡是由于至少两种杀虫化合物，厚朴酚和联苯醚。本研究将通过比较其解毒机制与无法耐受该寄主化学物质的两种同源植物的解毒机制来表征C. securifera对木兰的生理/生化适应性。体外和体内实验将用于鉴定酶解毒系统。此外，由于这三种Callosamia似乎最近才出现分化，并且在寄主利用方面有一些重叠，因此将对可能有利于寄主植物专门化的消化效率和解毒酶活性进行权衡。具体来说，预测1)专家比通才有更高的消化效率，2)通才比专家有更高的水平或3)广泛底物特异性解毒活性比专家更高的诱导性将被测试。随着对安全草处理寄主毒素的具体解毒机制的详细描述，有可能提出与寄主特化相关的生化权衡的更好假设。

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.