BRC-BIO: Looking beyond the calorie: Nutritional ecology in a generalist predator

卡路里通常被视为营养的主要单位，但越来越多的证据表明，食物的特定营养成分可能是野生动物觅食行为的更重要驱动因素。由于营养成分随环境条件的变化而变化，气候变化可能会影响食物的营养含量。对于捕食者来说，这意味着气候变化会改变猎物的营养，从而改变它们选择的猎物。然而，如果没有关于营养物质如何随着环境条件的变化而变化的基本知识，就很难预测捕食者的行为。鸣禽是许多生态系统中常见的捕食者，它们捕食各种昆虫，很容易捕获并观察它们的行为研究。该项目将1)评估猎物中的宏量营养素（蛋白质、碳水化合物、脂质），并确定最大化雏鸟生长的宏量营养素的特定比例；2)研究在实验操纵的环境条件下饲养猎物时，猎物的营养价值是如何变化的；3)研究营养变化是否会影响鸟类对猎物的偏好。由于昆虫被鸟类以外的许多动物食用，因此这项工作将对广泛的分类群具有保护意义。研究团队将包括攻读相关生物学课程的本科生和有偿本科生助理。学生将开发与更广泛的主题相关的独立项目，并前往国家会议展示他们的作品。这种研究经验将使参与者具备实验室和实地工作的技能，并建立学生坚持STEM职业的信心。研究人员将结合操作实验室实验和现有的100个东部蓝鸟巢箱网络，研究环境条件如何影响猎物的营养成分，以及这些变化是否影响捕食者的偏好。这项工作将测试营养几何框架的使用：营养几何框架是一种评估营养的工具，通过利用营养成分的比例来模拟食物如何组合以达到最大化生物体性能的多维营养目标。这个框架在模拟饮食如何随着不同食物在可得性或质量上的变化而变化时很有用。通过测量目标1中猎物常量营养素对雏鸟发育的影响，研究人员将确定最大化雏鸟生长的多维营养目标。在目标2中，这些数据将用于测试猎物的环境条件是否有意义地影响其营养含量。尽管一些研究调查了营养物质是如何随着温度或饮食变化而变化的，但很少有研究将它们结合起来，尽管气候变化预计会同时影响两者。在目标2中操纵饲粮和饲养温度的实验将促进我们对多种环境变化如何相互作用以决定营养价值的理解。最后，在目标3中，研究人员将使用基于营养改变的昆虫猎物的野外选择分析来检查蓝鸟的营养偏好。该项目的实验将通过检验营养几何框架和生活史理论的假设来推进营养生态学的基础科学，其结果将为保护应用提供信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Calories are often treated as the primary unit of nutrition, but a growing body of evidence suggests that the specific nutrient composition of food may be a more important driver of foraging behavior in wildlife. Because nutrient composition varies with environmental conditions, climate change is likely to affect nutrient content of food. For predators, this means that a changing climate could alter the nutrition of their prey, and therefore, what prey they select. However, without baseline knowledge of how nutrients shift in response to changing environmental conditions, it is difficult to make predictions about predator behavior. Songbirds are common predators in many ecosystems that prey on a variety of insects and can easily be captured and observed for behavioral studies. This project will 1) assess macronutrients (protein, carbohydrate, lipid) in prey and identify specific ratios of macronutrients that maximize nestling growth, 2) examine how the nutritional value of prey changes when reared in experimentally manipulated environmental conditions, and 3) examine whether changes in nutrition affect birds’ preference for prey. Because insects are consumed by many animals outside of birds, this work will have conservation implications for a wide range of taxa. The research team will include undergraduate students enrolled in relevant biology courses and paid undergraduate assistants. Students will develop independent projects related to the broader theme and travel to national conferences to present their work. This research experience will equip participants with skills in laboratory and field work and build students’ confidence to persist in STEM careers. Using a combination of manipulative laboratory experiments and an existing network of 100 Eastern bluebird nest-boxes, the researchers will examine how environmental conditions affect prey nutrient composition and whether these changes impact predator preference. This work will test the use of the nutritional geometric framework: a tool for assessing nutrition by utilizing ratios of nutrients to model how foods are combined to reach multidimensional nutritional targets that maximize organism performance. This framework is useful in modeling how diet changes as different food items change in availability or quality. By measuring the impact of prey macronutrients on nestling development in Objective 1, the researchers will identify multidimensional nutritional targets that maximize growth in nestlings. In Objective 2, these data will be used to test whether the environmental conditions of prey meaningfully impact their nutrient content. Although some studies investigate how nutrients change in response to temperature or diet shifts, very few examine these in combination, even though climate change is predicted to simultaneously affect both. Experiments in Objective 2 manipulating diet and rearing temperature will advance our understanding of how multiple environmental changes interact to determine nutritional value. Finally in Objective 3, researchers will examine bluebird nutritional preferences using field-based choice assays with nutritionally altered insect prey. The experiments in this project will advance basic science of nutritional ecology by examining hypotheses from the nutritional geometric framework and life history theory, the outcomes of which will inform conservation applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.