Feeding ecology of outbreak insect species

了解内源性（密度依赖）和外源性（密度独立）对种群动态的影响的性质和相对重要性仍然是生态学中的一个中心问题。由于种群密度变化的数据很少与资源测量相结合，因此很难比较自下而上和自上而下效应（分别为资源和天敌）的相对贡献，特别是在食草动物种群中。检验食物质量的变化是否在云杉芽虫种群动态中起作用的假设是我研究计划的长期目标。在短期内，我打算利用云杉芽虫-寄主树互作系统，研究食物质量对爆发昆虫剥叶虫种群适应性和种群动态的跨代效应。如果食物质量的变化对人口动态有影响，我预测跨代机制是这种影响的驱动力。相反，如果食品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，这种现象足够强大，可以使种群动态独立于食品质量变化。预计气候变化将导致温度升高和极端气候事件的频率增加，包括冬季的极端变化，如频繁的解冻事件。我预测，我打算在实验室中重现的这些预期的冬季解冻事件，将有利于当地适应食物质量的恶化，就像在爆发过程中发生的那样，通过对昆虫种群施加额外的选择压力，有利于更强壮、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芽虫的种群动态，我预测这些预期的新冬季条件将影响云杉芽虫种群的动态，或者至少影响它们的适应性。本研究项目的假设将通过饲养几代幼虫来验证，这些幼虫被安置在覆盖有套筒笼的寄主树枝上。将比较笼养种群和非笼养种群的结果。通过田间和室内的相互迁移试验，研究当地对食品质量的适应和冬季解冻的影响。该研究项目不仅有助于更好地理解食物在暴发食虫物种种群动态中的作用，而且有助于更好地了解气候变化和食物如何相互作用于昆虫种群动态和适合度。目前研究项目的结果将为制定旨在减少昆虫经济影响的森林管理措施提供有用的信息。此外，目前的研究将允许开发模型，可以预测由于气候变化而变化的环境中昆虫剥叶虫爆发的过程。

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.