EAPSI: Using Amino-acid Isotopes to Investigate Dietary Patterns and Specialization of Bats

了解动物的饮食对于确定形成其种群的生态和进化过程以及制定有效的保护措施至关重要。然而，由于难以评估食物来源，许多物种无法获得这类信息。根据该合同进行的研究将整合大量氮同位素和化合物特异性（氨基酸）氮同位素数据，以检查三种密切相关但知之甚少的迁徙蝙蝠物种（Lasiurus cinereus， Lasiurus borealis和Lasionycteris noctivagans）的营养位置和饮食宽度。这项工作将在日本海洋-地球科学技术机构（JAMSTEC）生物地球化学部门Naohiko Ohkouchi博士的实验室进行，该机构率先开发和应用氨基酸氮同位素分析来研究动物饮食。拟议的研究提供了一个无与伦比的机会来推进有关三种蝙蝠物种的饮食专业化程度与灵活性的研究。它还将率先将在美国本土机构无法获得的已建立的方法应用于一种新的研究系统（蝙蝠）。先前的研究对这些物种表现出的饮食专业化程度和灵活性的评估存在很大差异。其中一个原因是，之前的研究主要是基于对肠道和/或粪便物质内容的形态学分析，已知这只能检测到最近一顿饭中持久和可识别的猎物部分。稳定同位素分析克服了这一挑战，因为它整合了较长时期的饮食信息。从食物来源到消费者，氮同位素值逐渐增加，这为该方法提供了依据。然而，除了消费者的营养状况外，大块组织的氮同位素值也会受到食物网基准氮同位素值变化的影响。因此，我计划将大块组织氮同位素数据与氨基酸特定氮同位素数据相结合，这将使我能够区分这种“营养”和“源”效应。基于(1)初步的大量氮同位素数据（在家庭机构收集）和(2)对蝙蝠饮食和觅食生态学的现有知识，我假设这些蝙蝠的饮食习惯将显示出不同程度的专业化和饮食灵活性，以及一定程度的营养分化。更深入地了解这些物种的摄食行为和饮食灵活性，将有助于在全球环境变化的背景下更好地保护它们。该奖项隶属于东亚和太平洋暑期研究所项目，由美国国家科学基金会和日本科学促进会共同资助，支持一名美国研究生进行暑期研究。

Knowledge of the diets of animals is critical to identifying the ecological and evolutionary processes that shape their populations, as well as to developing effective conservation measures. However, such information is unavailable for many species because of difficulty in assessing food sources. The research conducted under this award will integrate bulk nitrogen isotope and compound-specific (amino-acid) nitrogen isotope data to examine the trophic positions and dietary breadth of three closely-related, but poorly understood, migratory bat species (Lasiurus cinereus, Lasiurus borealis, and Lasionycteris noctivagans). The work will be conducted in the lab of Dr. Naohiko Ohkouchi at the Department of Biogeochemistry at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which has pioneered the development and application of amino-acid nitrogen isotope analysis to the study of animal diet.The proposed research provides an unparalleled opportunity to advance research concerning the degree of dietary specialization vs. flexibility of three bat species of conservation concern. It would also pioneer the application of established methodologies that not available at the U.S. home institution to a novel study system (bats). Prior studies differ greatly in their assessment of the degree of dietary specialization vs. flexibility that these species exhibit. One reason is that prior studies have been largely based on morphological analysis of the content of gut and/or fecal material, which is known to only detect persistent and identifiable prey parts from a recent meal. Stable isotope analysis overcomes this challenge, because it integrates dietary information over a longer period. Nitrogen isotope values increase from food source to consumer, which provides the basis for this approach. However, besides the trophic status of a consumer, nitrogen isotope values of bulk tissue can also be influenced by variation in the baseline nitrogen isotope values of a food web. Thus, I plan to integrate bulk tissue nitrogen isotope data with amino-acid specific nitrogen isotope data, which will allow me to distinguish such 'trophic' and 'source' effects. Based on (1) preliminary bulk nitrogen isotope data (collected at the home institution) and (2) existing knowledge of bat diet and foraging ecology, I hypothesize that the dietary habits of these bats will indicate varying degrees of specialization and dietary flexibility, as well as some degree of trophic differentiation. Greater insight into the feeding behavior and dietary flexibility these species across their ranges would aid efforts to better conserve them in the context of global environmental change. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.