Energy management and life history evolution in variable environments

一个个体的能量状态被假设为对其生殖产出的核心影响，但能量测量通常是在实验室中进行的，远离其生态进化背景。因此，我的长期目标是了解环境变化如何影响野生动物的能量状态，并决定它们的繁殖分配决策。在这个授予周期内，我将实现三个短期目标：(1)确定环境和内在因素对准备繁殖时能量获取和同化水平变化的影响；(2)验证两种解释单次繁殖过程中生殖约束的能量机制假说；(3)揭示在整个生命周期中解释最优能量分配决策的繁殖事件之间的关系。我将使用最先进的移动实验室来描述两个已建立的野生哺乳动物研究系统（落基山地松鼠（RMGSP）和克鲁安红松鼠项目（KRSP））中个体的能量状态，以及对北极地松鼠（Urocitellus paryii）的新实地研究和对实验室小鼠（小家鼠）的圈养研究。具体来说，我将使用定量磁性身体成分分析仪来测量能量储存（脂肪和瘦肉质量），并使用开放流量呼吸仪来测量能量使用（代谢率）。在实地项目中，我们将在可量化的环境变化背景下，为充分人口普查的所有个体收集完整的生活史数据。在RMGSP中，我们将研究食物资源和天气的自然和人为变化对哥伦比亚地松鼠（U. columbianus）冬眠特征和生殖分配的影响。我们还将在一个共同的圈养环境中收集来自两个不同海拔的个体冬眠期间的详细能量数据。我将通过对北极野生地松鼠进行平行研究来评估这些发现的普遍性。在KRSP中，我们将评估缓存和体内资源变化的决定因素，以及这种变化如何影响红松鼠（Tamiasciurus hudsonicus）繁殖事件内部和之间的生殖分配。我们还将使用毛皮减少实验来验证在繁殖过程中限制消耗额外代谢产生的热量可以限制输出的假设。在实验室小鼠中，我将研究皮毛减少和卡路里限制对寿命和生殖产量的相互作用。生殖产出的变化是种群和微观进化动力学的核心组成部分，但导致这种变化的主要因素（能量状态）通常被视为“黑箱”。通过打开这个黑盒子，这项研究应该产生重要的基础和应用相关性的结果。

The energetic status of an individual is hypothesized to be a core influence on its reproductive output, but energetic measurements are typically made in laboratories, far removed from their eco-evolutionary context. My long-term goal is therefore to understand how environmental variation influences the energetic statuses of, and shapes the reproductive allocation decisions made by, wild animals. I will meet three short-term objectives over this granting cycle: (1) Determine the environmental and intrinsic influences on variation in levels of energy acquisition and assimilation in preparation for reproduction; (2) Test two hypothesized energetic mechanisms put forward to explain reproductive constraints during a single breeding event; and (3) Uncover relationships between breeding events that explain optimal energy allocation decisions across the lifetime. I will use a state-of-the-art mobile laboratory to characterize the energetic statuses of individuals within two established wild mammal study systems (the Rocky Mountain Ground Squirrel (RMGSP) and Kluane Red Squirrel Projects (KRSP)) as well as a new field study on Arctic ground squirrels (Urocitellus paryii) and a captive study on lab mice (Mus musculus). Specifically, I will use a quantitative magnetic body composition analyzer to measure energy stores (fat and lean mass) and open flow respirometry to measure energy use (metabolic rate). In the field projects, we will collect complete life history data for all individuals in fully censused populations against a backdrop of quantifiable environmental variation. In RMGSP, we will study the influences of natural and manipulated variation in food resources and weather on hibernation profiles and reproductive allocations of Columbian ground squirrels (U. columbianus). We will also collect detailed energetic data during hibernation of individuals from two different elevations in a common, captive environment. I will evaluate the generality of these findings by conducting a parallel study on wild Arctic ground squirrels. In KRSP, we will assess the determinants of variation in cached and on-body resources, and how this variation influences reproductive allocations made within and across breeding events in red squirrels (Tamiasciurus hudsonicus). We will also use a fur reduction experiment to test the hypothesis that limits on dissipating extra metabolically generated heat during reproduction can constrain output. In lab mice, I will study the interactive effects of fur reduction and calorie restriction on longevity and reproductive output. Variation in reproductive output is a central component in both population and microevolutionary dynamics, but a main contributor to this variation (energetic status) is typically treated as a `black-box'. By opening this black box, this research should produce results of both important fundamental and applied relevance.