A Critical Examination of the Model for Insect Body Size Determination: the Mechanisms of Body Size Variation in Bees

生长速度和停止生长的时间决定了身体的大小，这是生存和繁殖的重要特征。即使在经过充分研究的模式物种中，停止生长的线索也没有得到充分的理解。独居蜜蜂为它们的后代提供食物，限制了幼虫生长的食物。实验表明，完全食用这些食物会导致蜕变。研究独居蜜蜂变态的线索提供了一个独特的机会，可以从生理上比较相同年龄和大小的个体是否已经变态。这项拟议的研究将调查(1)孤独蜜蜂饥饿引发的变态背后的荷尔蒙线索是否与在达到特定大小后变形的昆虫中发现的相同；(2)变态时间的变化如何预测自然种群和不同蜜蜂物种中的身体大小变化；(3)蜜蜂成年大小的决定因素如何影响蜂王和蜜蜂工蜂之间的差异。蜜蜂的体型预示着授粉的表现，而对体型控制的生理学理解直接影响到自然和管理的蜜蜂物种的传粉者的健康和表现，无论是独居的还是群居的。本科生、研究生和博士后将参与这项研究，并将开发传粉者生命周期的K-12学习模块。体型是一种重要的生物特征，与表现和健康的大多数方面相关。在决定性生长的生物体中，身体的大小在成熟时是固定的；因此，调节成熟的机制也会影响个体之间的大小变化。昆虫作为幼虫生长，直到达到临界体重，此时调节变态的机制不可逆转地启动。这种已建立的身体大小控制模型可能不能推广到幼虫生态不同于模式昆虫物种的物种。初步数据表明，完全摄取幼虫食物会引发实蜂Osmia lignaria的变态。这一结果挑战了现有的昆虫身体大小的概念模型，表明临界重量并不是昆虫的普遍特征。拟议的研究将针对三个中心目标：1)表征独居蜜蜂变态的生理调节；2)表征决定相似幼虫生态的独居蜜蜂种群和物种之间体型差异的因素；以及3)测试食量对群居蜜蜂种级差异的影响程度。这些机制有可能解释观察到的膜翅目昆虫之间的大部分体型差异。最后，拟议的研究将从机械上明确理解蜜蜂的身体大小决定，蜜蜂是自然和管理生态系统的关键传粉者。对体型变化的更深入、机械性的理解可能会在个人甚至种群的规模上为改善传粉者的健康带来洞察力。这些研究的结果将在同行评议的期刊上传播，并通过在科学会议上的陈述来传播。

Growth rate and the timing of when growth stops determine body size, an important trait for survival and reproduction. The cues that stop growth are not fully understood, even in well-studied model species. Solitary bees provision their offspring, restricting the food available for larval growth. Experiments indicate that the complete consumption of these provisions induces metamorphosis. Studying the cues to metamorphosis in solitary bees provides a unique opportunity to physiologically compare individuals of the same age and size that either have or have not transitioned to metamorphosis. The proposed research will investigate (1) whether the hormonal cues underlying starvation-triggered metamorphosis in solitary bees are the same as those found in insects that metamorphose upon reaching a particular size, (2) how variation in the timing of metamorphosis predicts body size variation in natural populations and different bee species, and (3) how the determinants of adult size in bees shape differences between queens and workers in honeybees. Bee body size predicts pollination performance, and a physiological understanding of body size control has direct implications for pollinator health and performance in both natural and managed bee species, whether solitary or social. Undergraduates, graduate students and a postdoctoral fellow will participate in this research, and K-12 learning modules on pollinator life cycles will be developed.Body size is an important organismal trait that correlates with most aspects of performance and fitness. In determinant-growing organisms, body size becomes fixed at maturation; therefore the mechanisms regulating maturation also influence size variation among individuals. Insects grow as larvae until attainment of a critical weight, at which point the mechanisms regulating metamorphosis are irreversibly initiated. This established model of body size control may not be generalizable to species with larval ecologies that differ from model insect species. Preliminary data demonstrate that completely consuming the larval provision initiates metamorphosis in the solidary bee Osmia lignaria. This result challenges the existing conceptual model for insect body size by suggesting that the critical weight is not a universal trait in insects. The proposed research will address three central aims: 1) characterizing the physiological regulation of metamorphosis in the solitary bee Osmia lignaria, 2) characterizing factors determining body size variation among populations and species of solitary bees that share similar larval ecologies; and 3) testing the degree to which diet quantity contributes to caste differences in eusocial bees. These mechanisms have the potential to explain much of the body size variation observed among Hymenopterans. Finally, the proposed research will develop a mechanistically explicit understanding of body size determination for bees, which are key pollinators for natural and managed ecosystems. A deeper, mechanistic understanding of body size variation may yield insights into improving pollinator health at the scale of individuals or even populations. Results from these studies will be disseminated in peer reviewed journals and through presentations at scientific meetings.