Feeding ecology of outbreak insect species

田间和室内饲养试验结果表明，香脂冷杉叶片总鞣质组分可能是寄主对云杉芽虫的抗性机制之一。然而，所涉及的具体单宁及其各自的作用方式仍有待研究。我推测，特定的叶面单宁通过干扰幼虫的食物利用过程，协同作用影响幼虫的生存和生长，并且这些特定的单宁对幼体有不同的作用模式。这一假设将通过重量、行为、电生理和组织学研究来验证，这些研究是在人工饲料中添加不同水平和组合的从树叶中提取的纯化学物质的幼虫饲养的。根据局部适应假说，长寿命植物种群中营养、防御或物候性状的空间异质性将短命的专门食草动物种群结构成适应个体寄主表型的deme（遗传上不同的种群）。我假设，在疫情爆发期间，食物质量恶化（由连续的昆虫落叶引起的宿主表型变化）对budworm种群施加了选择压力，从而改变了种群的基因频率，从而导致更好地适应恶劣的摄食条件。在实验室条件下，利用昆虫滞育后的兄弟姐妹和受损林分的新鲜叶片或未受损林分的叶片，对连续四代昆虫进行互惠转移实验。云杉budworm生物学性能将被记录和定量遗传分析进行。将使用高质量和低质量饲料进行更多的实验室饲养试验，以调查营养胁迫对云杉芽虫几代影响的过程。我假设，通过选择压力，在几代云杉芽虫上施加的营养压力改变了幼虫的发育和食物利用，最佳营养平衡和对积极和消极食物质量变化的反应（营养和次级化合物）。

Results from field and laboratory rearing experiments indicate that total tannin fraction of balsam fir tree foliage appears to serve as mechanisms of host resistance to spruce budworm. However, the specific tannins involved and their individual mode of action remain to be investigated. I hypothesize that specific foliar tannins act synergically to influence larval survival and growth by interfering with larval food utilization processes and that these specific tannins have different modes of action on budworm larvae. This hypothesis will be tested using gravimetric, behavioral, electrophysiological, and histological studies on larvae reared on artificial diet supplemented with various levels and combinations of pure chemicals extracted from foliage. According to the local-adaptation hypothesis, the spatial heterogeneity in nutritive, defensive, or phenological traits within populations of long-lived plants structures populations of short-lived, specialized herbivores into demes (genetically different populations) adapted to the phenotypes of individual hosts. I hypothesize that food quality deterioration (change in host phenotype caused by successive insect defoliation) during an outbreak exerts a selective pressure on budworm population that changes gene frequency of the population which in turn leads to a better adaptation to poor feeding conditions. Reciprocal transfert experiments will be conducted over four successive generations of insect under laboratory conditions using postdiapausing siblings and fresh foliage from damaged stands or foliage from undamaged stands. Spruce budworm biological performances will be documented and quantitative genetic analysis performed. Additional laboratory rearing experiments will be conducted using high and low quality diets to investigate the processes involved in the impact of nutritional stress on spruce budworm over several generations. I hypothesize that, through selective pressure, nutritional stress imposed on spruce budworms over several generations modifies larval development and food utilization, optimal nutrient balance and responses to positive and negative food quality changes (nutrient and secondary compounds).