Spatial dynamics of an Outbreaking Insect Population

哈里森理论模型预测种间相互作用，结合有限的扩散，有时可能会产生稳定的种群密度的空间格局。 这项研究的重点是草食性昆虫，往往形成密集的，但非常本地化，人口在其寄主植物的较大面积。 以前的工作已经确定，这种昆虫，西部草丛蛾，是一个非常差的扩散，它的空间分布并没有出现的可变栖息地质量的解释。 本研究探讨了两种非排他性的方式，所观察到的模式可能会出现从蛾和它的天敌之间的相互作用：（1）捕食者饱足，其中移动的较差的多面手捕食者（蚂蚁）在猎物密集的地方比在猎物稀疏的地方对猎物造成更高的死亡率，和（2）捕食者扩散，其中移动的，专门的天敌（两种寄生虫）“溢出”密集的猎物种群的边缘，创造周围的区域，捕食者-猎物的比例，因此死亡率，提高。 初步的现场结果表明，这两种机制可能都在发挥作用，但不知道它们是否足以抑制疫情的传播。 本研究采用实地实验结合模拟和分析建模来测试这些解释的空间人口格局。 了解控制种群密度的因素仍然是生态学的核心问题。 特别是，识别害虫物种流行密度的原因，应大大提高控制未来爆发的能力，从而减少此类事件造成的生态和经济损失。

9628937 Harrison Theoretical models predict that interspecific interactions, combined with limited dispersal, may sometimes produce stable spatial patterns in population densities. This study focuses on a herbivorous insects that tends to form dense, but very localized, populations within larger areas of its host plant. Previous work has established that this insects, the western tussock moth, is a very poor disperser, and that its spatial distribution does not appear to be explained by variable habitat quality. The present study examines two non-exclusive ways that the observed pattern could arise from interactions between the moth and its natural enemies: (1) Predator satiation, in which a poorly mobile, generalist predator (an ant) inflicts higher mortality on prey where prey are dense than where they are sparse, and (2) Predator diffusion, in which mobile, specialized natural enemies (two parasitoids) "spill over" around the edges of dense prey populations, creating surrounding zones in which predator-prey ratios, and therefore mortality, are elevated. Preliminary field results indicate both these mechanisms may be operating, but not whether they are strong enough to suppress the spread of outbreaks. This study uses field experiments combined with simulation and analytic modeling to test these explanations for spatial population patterns. Understanding the factors that govern population densities remains a central issue in ecology. In particular, discerning the causes of epidemic densities of pest species, should greatly enhance the ability to control future outbreaks and thus lessen the ecological and economic damage from such events.