Feeding ecology of outbreak insect species

了解内源(密度相关)和外源(密度无关)效应对种群动态的性质和相对重要性仍然是生态学中的一个中心问题。自下而上和自上而下的影响(分别是资源和天敌)的相对贡献，特别是在食草动物种群中的相对贡献一直很难比较，因为关于种群密度变化的数据很少与资源测量相结合。检验食物质量变化是否对云杉芽孢子虫种群动态起作用的假设代表了我的研究计划的长期目标。在短期内，我打算利用云杉芽孢子虫-寄主树木相互作用系统来研究食物质量对暴发害虫种群适合度和种群动态的跨代影响。如果食品质量的变化有助于人口动态，我预测跨代机制是这种贡献的驱动力。相反，如果食物质量对种群动态没有贡献，我预测，跨代效应会产生一种局部适应现象，这种现象足够强烈，使种群动态独立于食物质量变化。气候变化预计将导致气温上升和极端气候事件的频率增加，包括冬季的极端变化，如频繁的融化事件。我预测，这些预期中的冬季融化事件--我打算在实验室中重现--将通过对昆虫种群施加额外的选择性压力，有利于当地适应食物质量的恶化，就像在疫情爆发期间发生的那样，从而有利于更强大、更适应不良营养的昆虫。无论过去食物质量是否驱动了云杉潜蝇的种群动态，我预测这些预期的新冬季条件将影响云杉幼虫的种群动态，或者至少影响它们的适合度。这项研究项目的假设将通过饲养安装在用袖笼覆盖的寄主树枝上的幼虫进行多次世代的检验。笼养和非笼养种群的结果将进行比较。将通过田间和实验室的相互转移试验来研究当地对食物质量的适应和冬季融化的影响。这一研究计划不仅有助于更好地了解食物在暴发害虫种群动态中的作用，也将有助于更好地了解气候变化和食物对昆虫种群动态和适合度的影响。当前研究方案的结果将为制定旨在减少昆虫经济影响的森林管理实践提供有用的信息。此外，目前的研究将允许开发能够预测由于气候变化而变化的环境中昆虫落叶虫暴发过程的模型。

Understanding the nature and relative importance of endogenous (density-dependent) and exogenous (density-independent) effects on population dynamics remains a central problem in ecology. The relative contributions of bottom-up and top-down effects (resources and natural enemies, respectively), particularly in herbivore populations, have been difficult to compare because data on population density variation have rarely been combined with resource measurements. Testing the hypothesis of whether or not variation in food quality plays a role in spruce budworm population dynamics represents the long-term objective of my research program. In the short-term, I intend to study trans-generational effects of food quality on outbreak insect defoliator population fitness and population dynamics using the spruce budworm-host tree system of interactions. If food quality changes contribute to population dynamics, I predict that the trans-generational mechanism is the driving force of that contribution. In contrast, if food quality does not contribute to population dynamics, I predict that trans-generational effects generate a locally adaptative phenomenon that is strong enough to render population dynamics independent of food quality variation. Climate change is expected to cause increases in temperature and in the frequency of extreme climatic events, including extreme variation during winter, such as frequent thaw episodes. I predict that these anticipated winter thaw episodes, which I intend to reproduce in the laboratory, would favor local adaptation to food quality deterioration, as would occur during the course of an outbreak, by exerting additional selective pressure on insect populations in favor of stronger, more adaptable insects to poor quality nutrition. Whether food quality has or has not driven population dynamics of spruce budworm in the past, I predict that these expected new winter conditions would affect the dynamics of spruce budworm populations or at least, their fitness. The hypotheses of this research project will be tested by rearing, over multiple generations, larvae installed on host branches that were covered with sleeve cages. Results from caged and uncaged populations will be compared. Local adaptation to food quality and effects of winter thaw will be investigated using field and laboratory reciprocal transfer experiments. This research program will contribute not only to a better understanding of the role of food in the population dynamics of outbreak insect defoliator species, but also to a better understanding of how climate change and food interact on insect population dynamics and fitness. Results of the current research program will provide information useful to develop forest management practices aimed at reducing insect economic impact. Also, the current research will allow the development of models that can predict the course of insect defoliator outbreaks in a changing environment due to climate alterations.