DISSERTATION RESEARCH: Sodium availability and the structure of brown food webs

钠（Na）是一种重要的营养物质，对植物来说相对不重要，但对动物的神经功能、繁殖和发育至关重要。然而，随着与海洋距离的增加，环境中na的可用性降低。钠通过排泄不断流失，必须不断消耗以维持钠平衡。在食物链中处于较低位置的生物，如食草动物，从它们的饮食中获得的钠很少，而捕食者则以猎物的含盐食物为食。因此，严格的食草动物经常在缺乏钠的内陆环境（约占地球表面的80%）中受苦。由于从植物到捕食者，活组织中的钠浓度会增加，因此动物本身在任何环境中都是钠的丰富来源。提议的田野调查测试了杂食动物（既吃植物又吃动物的生物）在Na稀缺时通过按比例消耗更多动物来维持Na平衡的假设。这项研究通过在美国乔治亚州到缅因州的沿海-内陆配对（na富与na贫）地点取样蚂蚁来验证这一假设。蚂蚁是评估物种和地点特定食物链位置的理想选择，因为它们无处不在，主要是杂食性的。本研究的实验室部分通过直接实验进一步验证了这一假设。在这里，蚁群将只喂食不同钠含量的食物，以确定钠饥饿和捕食的程度。这个项目的结果可能会产生一个新的理论来源管理杂食性物种的饮食。本研究将透过有监督的实地研究及科学传播方面的训练，促进本科生的专业发展。参与的本科生将帮助进行实验，学习管理数据并识别大约100种蚂蚁。此外，本科生助理将有机会通过在地方和国家会议上的演讲来传达本研究的结果，并获得出版物的合著者身份。最后，这项拟议的研究将生成北美东部纬度约15度以上蚂蚁物种的地理明确数据。本次研究的代金券将被存放在萨姆·诺布尔自然历史博物馆（诺曼，OK）和作者的收藏中，以便将来的研究使用。

Sodium (Na) is an essential nutrient relatively unimportant for plants but critical for animal neural function, reproduction and development. However, environmental Na-availability decreases as the distance from an ocean increases. Na is constantly lost through excretion and must constantly be consumed to maintain a Na-balance. Organisms feeding low in food chains, such as herbivores, obtain little Na from their diet whereas predators consume salty diets of prey. As such, strict herbivores often suffer in Na-poor, landlocked environments (ca. 80% of earth's surface). Since Na concentration in living tissue increases from plants to predators, animals themselves are an abundant source of Na in any environment. The proposed fieldwork tests the hypothesis that omnivores (organisms that consume both plants and animals) maintain a Na-balance by consuming proportionally more animals when Na is rare. This study tests this hypothesis by sampling ants at paired coastal-inland (Na-rich vs. Na-poor) sites from Georgia to Maine, USA. Ants are ideal to assess species- and location-specific food chain position because they are ubiquitous and mainly omnivorous. The lab component of this study further tests this hypothesis through direct experimentation. Here, ant colonies will be fed diets only differing in Na content to determine the extent to which Na-hunger and predation can be induced. The results of this project may generate a new source of theory governing the diets of omnivorous species. This study will facilitate the professional development of an undergraduate through supervised field research and training in scientific communication. The participating undergraduate will help conduct the experiment, learn to manage data and identify ca. 100 species of ants. Additionally, the undergraduate assistant will have the opportunity to communicate the results of this study through presentations at local and national meetings and earn co-authorship on publications. Finally, the proposed study will generate geographically explicit data for ant species over ca. 15 degrees in latitude along Eastern North America. Vouchers from this study will be deposited in the Sam Noble Museum of Natural History (Norman, OK) and author's collections and thus available for future research.