Do migrant moth species have adaptations that reduce the cost of long distance flight on future reproduction?

对几种表现出翅膀多态的昆虫物种(既有有翼也有无翼的变种)的研究表明，没有翅膀的成虫的繁殖产量高于从不断恶化的栖息地迁徙出来的有翼成虫。这些结果被解读为支持这样的观点，即飞行是以繁殖为代价的。然而，在所有成虫都有翅膀并需要飞行才能找到食物、配偶和产卵地点的物种中，这一点没有得到仔细的检查。此外，人们还假设，迁徙物种已经进化出了一些特征，以降低在随后的繁殖产出中维持飞行设备的成本。在我的研究小组中，我们一直在使用真正的粘虫，P.unipuncta，其中所有的成虫都有功能的翅膀，作为一个模型系统来研究信息素介导的交配，并表明迁徙(北美)和非迁徙(亚速尔)种群之间存在显著的行为和生理差异。我们将使用北美(NA)迁徙人口以及来自亚速尔群岛(AZ)和夏威夷(HA)的非迁徙人口，来检验在单态物种中繁殖的逃亡成本，并检验移民已经进化出特征以降低迁移成本的假设。我们将比较夏季(非候鸟)和秋季(候鸟)在人工饲料和自然寄主植物上在实验室不同控制条件下和在自然田间条件(杀虫剂)下饲养的NA个体。我们将测试形态上的差异(翅膀大小，胸部质量)，以确定是否存在飞行机械(肌肉/翅膀)的差异分配，并研究不同飞行时间对非迁徙动物和飞行前后喂食不同糖类的迁徙动物繁殖力的影响。这些实验将使我们能够确定是否有与迁徙相关的生殖成本，以及迁徙后的喂养和交配是否可能减轻这些成本。我们还将检查胸肌，以确定居民和迁徙(来自自然种群和田间饲养)之间是否存在结构和/或生理差异，以确定迁徙是否具有降低繁殖飞行成本的修饰。这些实验将在来自AZ和HA的非移民个体身上重复，因为AZ的成年个体较小，在较小的年龄成到性成熟，但其一生的生殖输出明显高于来自NA的个体。 我们最近的工作表明，与信息素介导的交配相关的行为在三个不相关的物种中随着大气压力(AP)的短期变化而改变。我们现在将检验这样的假设：粘虫成虫的飞行倾向不仅会受到与季节变化相关的线索的影响，而且还会对AP的每日波动做出反应，这些波动提供了可靠的飞行条件指标。

Studies on several insect species exhibiting wing polymorphism (having both winged and wingless morphs) have shown that the reproductive output of wingless adults is higher than their winged counterparts that migrate out of deteriorating habitats. These results have been interpreted as supporting the idea that flight comes at a cost to reproduction. However, this has not been examined carefully in species where all adults are winged and require flight for the location of food, mates and oviposition sites. Furthermore, it has been hypothesized that migrant species have evolved traits to reduce the cost of maintaining flight apparatus on subsequent reproductive output. In my research group we have been using the true armyworm, P. unipuncta, where all adults have functional wings, as a model system to study pheromone mediated mating and have shown there are marked behavioural and physiological differences between migratory (North America) and non-migratory (Azores) populations. We will use the North American (NA) migrant population, and non migrant populations from the Azores (AZ) and Hawaii (HA), to examine the cost of flight on reproduction in a monomorphic species and to test the hypothesis that migrants have evolved traits to reduce the costs of migration. We will compare NA individuals reared under different controlled conditions in the laboratory and under natural field conditions (insectary) on both artificial diet and natural host plants during the summer (non-migrants) and fall (migrants). We will test for differences in morphology (wing size, thoracic mass) to determine if there is differential allocation to flight machinery (muscle/wings) and examine the effect of flight of different durations on the fecundity of non-migrants and migrants fed different sugar regimes before and after flight. These experiments will allow us to determine if there are reproductive costs associated with migration and whether post-migratory feeding and mating might mitigate them. We will also examine thoracic muscle to determine if there are structural and/or physiology differences between residents and migrants (from natural populations and field rearings) to determine if migrants have modifications that reduce the costs of flight on reproduction. These experiments will be repeated with non migrant individuals from AZ and HA, as AZ adults are smaller and become sexually mature at a younger age, yet have a significantly higher life time reproductive output than those from NA. Our recent work has shown that the behaviours associated with pheromone mediated mating in three unrelated species changed in response to short term changes in atmospheric pressure (AP). We will now test the hypotheses that flight propensity of adult armyworm moths will be not only be affected by cues associated with seasonal change, but also in response to daily fluctuations in AP that provide reliable indicators of flight conditions.