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

钠(Na)是一种基本的营养物质，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，随着离海洋距离的增加，环境中的钠有效性降低。钠在排泄过程中不断流失，必须不断消耗才能维持钠平衡。食物链较低的生物，如食草动物，从他们的食物中几乎没有获得钠，而捕食者吃的是猎物的含盐食物。因此，严格的食草动物通常在贫瘠的内陆环境中受苦(约占地球表面的80%)。由于从植物到捕食者，活组织中的钠浓度都在增加，因此动物本身在任何环境中都是钠的丰富来源。这项拟议的田野工作测试了一种假设，即杂食性动物(既吃动植物又吃动物的有机体)通过在钠稀少的情况下按比例摄入更多的动物来维持钠平衡。这项研究通过在从佐治亚州到缅因州的沿海-内陆(富钠和贫钠)配对地点的蚂蚁样本来验证这一假设。蚂蚁是评估特定物种和特定位置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。这项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，蚂蚁群将被喂养只有钠含量不同的食物，以确定能在多大程度上诱导钠饥饿和捕食。这个项目的结果可能会产生一个管理杂食性物种饮食的新的理论来源。这项研究将通过监督实地研究和科学沟通方面的培训，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发表演讲来交流这项研究的结果，并在出版物上获得联合作者资格。最后，这项拟议的研究将为北美东部纬度约15度以上的蚂蚁物种生成地理上明确的数据。这项研究的凭证将存放在萨姆·诺布尔自然历史博物馆(诺曼，俄克拉荷马州)和作者的收藏品中，从而可用于未来的研究。

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.