Evolution of Specificity in Insect/Plant Interactions

需要资金用于研究植食性昆虫在转移到新宿主的过程中如何进化产卵偏好和专一性。目前昆虫寄主选择的理论认为，产卵的雌虫在潜在寄主植物中表现出偏好等级，并根据等级顺序排列。然后，寄主转移开始于：(A)偏好等级中的遗传变化，(B)降低对高等级寄主的专一性程度从而扩大寄主范围的遗传变化，或(C)在没有较高等级且偏好遗传变化很少或没有遗传变化的植物的情况下，在偏好等级较低的植物上定居。最近对以不同植物科为食的两个密切相关的燕尾蝴蝶物种Papilio zelicaon和P.oregonius的研究表明，这两个物种表现出相当不同的偏好等级。然而，对该物种复合体内其他种群的初步研究表明，一些寄主转移可能不涉及偏好层次结构中的完全重排，而是反映了对可用寄主的专一性程度或行为反应的变化。这种变异提供了一个机会来询问，随着马尾松物种复合体中的种群多样化到不同的寄主植物上，偏好等级发生了多少重新安排。因此，这项拟议的工作将提出一个问题，即根据泽利卡松和奥雷戈尼乌斯种间差异得出的产卵偏好进化结论是否适用于北美马尾松物种复合体的种群分化和物种形成。目标1将询问马尾松复合体中以伞形幼虫为食的物种在对植物物种的偏好层次上有何不同。也就是说，新主机的殖民是否总是涉及首选项层次结构的重新排序，如果不是，哪些主机需要这样的重新排序？目标2将询问斑潜蝇种群的喜好等级是否有所不同。凤蝶种群在不同的寄主植物上存在地理差异。因此，可以将目标1的种间结果与本节中的种内结果进行比较。最后，目标3将询问不同种群间喜好等级的差异是否作为X连锁基因座遗传，就像种群间的差异一样。最近发现的主要种间差异主要是X连锁的，这首次为比较寄主偏好的种内差异的遗传方式和观察到的种间差异的遗传方式提供了机会。汤普森一起，这三个目标的结果将有助于昆虫/植物相互作用理论的发展，因为它解决了昆虫种群在新寄主植物上定居时产卵偏好如何变化的根本问题。由于许多昆虫多样性似乎是由于对不同寄主物种的分化而产生的，因此拟议的工作也解决了昆虫多样性的起源问题。

Funds are requested for a study of how oviposition preference and specificity evolve in phytophagous insects during shifts onto new hosts. Current theory for host choice in insects holds that ovipositing females exhibit a preference hierarchy among potential host plants and according to the rank order in the hierarchy. Host shifts then begin either as (a) genetic shifts in the preference hierarchy, (b) genetic changes that decrease the degree of specificity to highly ranked hosts and thereby broaden the range of hosts, or (c) colonization of plants lower on the preference hierarchy in the absence of more highly ranked plants with little or no genetic change in preference. Recent work on two closely-related swallowtail butterfly species, Papilio zelicaon and P. oregonius, that feed on different plant families showed that these species exhibit quite different preference hierarchies. Preliminary studies of other populations within this species complex, however, indicate that some host shifts may not involve complete rearrangements in preference hierarchy but instead reflect changes in degree of specificity or behavioral responses to available hosts. This variation provides an opportunity to ask how much rearrangement of the preference hierarchy has occurred as populations in the P. machaon species complex have diversified onto different host plants. Therefore, the proposed work will ask if the conclusions on the evolution of oviposition preference drawn from interspecific differences between P. zelicaon and P. oregonius apply to population differentiation and speciation throughout the P. machaon species complex in North America. Objective 1 will ask how umbellifer-feeding species of the P. machaon complex differ in their preference hierarchy for plant species. That is, has colonization of new hosts always involved a reordering of the preference hierarchy and, if not, which hosts have required such a reordering? Objective 2 will ask if populations of P. zelicaon differ in their preference hierarchy. Papilio zelicaon populations differ geographically in their host plants. Consequently, it is possible to compare the interspecific results from objective 1 with intraspecific results in this section. Finally, Objective 3 will ask whether differences in preference hierarchy among populations of P. zelicaon are inherited as X- linked loci as are the interspecific difference between P. zelicaon and P. oregonius. The recent finding that the major interspecific differences are primarily X-linked provides for the first time the opportunity to compare the mode of inheritance of intraspecific divergence in host preference with that observed for interspecific divergence. Thompson Together, the results for the three objectives will aid in the development of the theory of insect/plant interactions by addressing the fundamental problem of how oviposition preference diverges as insect populations colonize new host plants. Since much of insect diversity appears to arise from divergence onto different host species, the proposed work therefore also addresses the problem of the origins of insect diversity.