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体型，这是生存和繁殖的重要特征。停止生长的线索还没有被完全理解，即使是在经过充分研究的模式物种中也是如此。独居的蜜蜂为它们的后代提供食物，限制了幼虫生长所需的食物。实验表明，完全食用这些食物会引起变态。研究独居蜜蜂的变态线索提供了一个独特的机会，从生理学上比较相同年龄和体型的个体，这些个体要么已经过渡到变态，要么没有过渡到变态。该研究将调查(1)孤独蜜蜂中饥饿引发的变态背后的激素线索是否与在达到特定尺寸后变态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的体型变化，以及(3)决定成年蜜蜂体型的决定因素如何塑造蜂王和工蜂之间的差异。蜜蜂的体型大小可以预测传粉的表现，对体型控制的生理学理解对自然和人工管理的蜜蜂物种（无论是独居的还是群居的）传粉者的健康和表现都有直接的影响。本科生、研究生和一名博士后将参与这项研究，并将开发有关传粉媒介生命周期的K-12学习模块。体型是一个重要的有机体特征，与大多数方面的表现和健康有关。在决定性生长生物中，体型在成熟时变得固定；因此，调节成熟的机制也影响个体之间的大小差异。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。这种建立的体型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。初步的数据表明，完全消耗幼虫供应会引起木质素蜂群的变态。这一结果挑战了现有的昆虫体型概念模型，表明临界体重不是昆虫的普遍特征。拟开展的研究将围绕三个中心目标展开：1)描述木质素独居蜂（Osmia lignaria）变态的生理调控；2)描述具有相似幼虫生态的独居蜂种群和物种之间体型变化的决定因素；3)检验食用量对蜂群等级差异的影响程度。这些机制有可能解释在膜翅目昆虫中观察到的身体大小变化。最后，提出的研究将发展对蜜蜂身体大小决定的机械明确的理解，蜜蜂是自然和管理生态系统的关键传粉者。对身体大小变化的更深入的、机械的理解可能会产生在个体甚至群体的尺度上改善传粉者健康的见解。这些研究的结果将在同行评议的期刊上传播，并在科学会议上发表报告。

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.