莲草直胸跳甲不同地理种群热适应性的生理生殖响应机制

Heat stress is the driving force of adaptive evolution in insects. Population dynamics of Agasicles hygrophila, a biological control agent of alligator weed, differ in different geographic populations. In China, its population decreases to a very low density in the field in summer. Whereas in Thailand, its population density keeps high even in summer, indicating that the Thailand population has heat tolerance under tropic climates. In view of this phenomenon, we will use the theories and techniques of population ecology, morphology, biochemistry, analytical chemistry and immunohistochemisty, to reveal the countermeasure between defense and reproduction of the two A. hygrophila populations under high temperatures. Life-table parameters under their optimal and stress temperatures will be compared for multiple generations. Heat shock protein gene expression, contents of defensive polyols (mannitol and sorbitol) and carbohydrate (trehalose), activities of protective enzymes (superoxide dismutase, peroxidase, catalase) in each generation will be measured. Morphology of reproductive system, development of ovary and testis, and the oogenesis of the two populations will be observed, and yolk protein level at different developmental stages will be detected after the development of vitellin antibody. Contents of neurohormones (juvenile hormone and moulting hormone) will also be detected. By such a serial of comparisons of physiological metabolism and reproductive regulation between the two populations under high temperatures, we aim to reveal the adaptive mechanisms of the Thailand population to high temperatures. These results will enrich the theories of insect adaptive evolution and will support the biological control practices of alligator weed management.

温度胁迫是昆虫种群适应性进化的动力。莲草直胸跳甲是空心莲子草的专食性天敌昆虫，本项目针对该跳甲在我国夏季种群骤减而其泰国种群具有耐热性这一现象，围绕不同地理种群莲草直胸跳甲在高温胁迫下的资源利用与种群调节这一科学问题，以泰国种群和我国种群为对象，采用种群生态、形态学、生物化学、分析化学和免疫组织化学等方法， 比较两个种群在适温和高温胁迫条件下连续多代的生命表参数，探明其热适应性差异，生活史发育和形态等生态可塑性特征；定量分析其响应高温的生理生化特征和保护机制，解析热激蛋白、多元醇、糖类化合物、保护酶等的作用；比较其响应高温的生殖行为、内生殖器官发育、卵子和卵黄发生过程及神经激素含量，解析两个种群生殖潜能差异及其内分泌调控机制。研究结果对于揭示莲草直胸跳甲不同地理种群的热适应性差异及其响应高温的资源利用权衡与种群调节机制，进行种群优化和高效利用具有重要意义，并有助于丰富昆虫适应性进化理论。

本项目针对空心莲子草天敌莲草直胸跳甲在我国华中、华东等地区夏季种群骤减这一问题，比较研究了海南万宁和湖南长沙两个地理种群的热适应性。经多代高温胁迫后，万宁种群发育、繁殖及生命表参数明显优于长沙种群。通过转录组测序、耐热生理及分子机制的初步分析和探讨，解析了两个地理种群耐热性存在差异的主要原因。研究结果丰富了昆虫适应性进化理论，为莲草直胸跳甲的种群优化和高效生防应用提供理论和实践依据。