三化螟种群的内稳定性及其生态机制

从三化螟世代转换及其与水稻生长发育进程的相互作用体系, 分析了三化螟种群的内稳定性及其生态机制。结果表明, 在各类稻作区, 不同年份之间, 历代成虫数量发生型显著不同, 但其发生期具有共同的特征: 2代蛾的发生期（≥27天）比1代蛾大幅度扩展, 且相对稳定。发蛾期扩展的机制在于: 同期初孵幼虫在寄主水稻中异步化发育, 极端发育进度相差达3龄期; 在9.92、镇稻2号等10个不同品系的寄主水稻中, 异步化程度存在显著差异。基于异步化发育, 三化螟种群的时间生态位增加22.0%～75.0%, 二维生态位扩展15.1%～59.3%, 并使同一种群中极端早发类与迟发类的后代可交配, 以此保持种群遗传性的相对稳定。针对三化螟种群内稳定性形成的机制与条件, 提出了种群的数量与结构控制相结合的系统控害策略与技术。

Ecological mechanism for population homeostasis of the yellow stem borer, Scirpophaga incertulas

Based on analysis of interaction between the yellow stem borer (YSB), Scirpophaga incertulas (Walker) and its host rice, ecological mechanism for homeostasis of the insect population in its successive generations was investigated. The result showed that yearly pattern of the moth occurring durations among generations a year was similar although dynamics of their number was different in Wujin County, Jiangsu Province and Hexian County, Anhui Province with distinct rice cropping systems. Duration of the 2nd generation moth in the field was always ≥27 days, much longer than that of the 1st generation in different years. The duration increment mainly resulted from different developing rates of larvae even in the plants of the same rice variety, with an extreme stage difference of 3 instars after the neonates infesting into the rice for 20 days. The asynchronous development of YSB larvae in the host led to the evidently increase in temporal niche of the population by 22.0%～75.0%, which counteracted the decrease of its spatial niche due to the larval mortality. Consequently dual dimension niche of the population expanded by 15.1%～59.3%. The asynchronous development also made it feasible to mate between the offsprings of the earliest and the latest occurring moths, so as to produce a combined type of YSB. It was probable that homeostasis of the YSB population was genetically kept by the combined type and its offsprings which would avoid genetic drift of the population in extreme climates such as a earlier emerging spring. Finally, the strategy and key techniques for systematic management of YSB population in both quantity and quality of YSB population have been established and well practiced in certain areas on the basis of these researches.