DISSERTATION RESEARCH: Investigating species interactions across 15,000 years of extinctions and invasions: an isotopic approach

地球上纵横交错的高速公路和航线正在通过引入非本地物种侵蚀曾经分隔生物群落的界限。这些入侵物种给美国带来了经济和生态成本，损害了农业、渔业和我们的标志性景观。在岛屿上，这些入侵者更加有害，经常与本地物种竞争或吃掉它们，使其濒临灭绝，从而不可逆转地破坏了生物多样性热点地区。在这个项目中，研究人员将采用一种创新的方法，通过结合15000年前的化石和现代标本的数据，来了解入侵物种的后果。利用在多米尼加共和国出土的化石，研究人员将重建史前人类（6000年前）到来前后、欧洲人（500年前）到来以及随之而来的入侵物种到来前后的本地哺乳动物物种（如树懒、猴子和啮齿动物）的生态互动。本地物种如何应对灭绝的基线将为了解入侵物种在现代生态系统中的位置提供背景。例如，像山羊这样的入侵食草动物消耗的植被是否与灭绝的本土树懒消耗的植被相似？该研究将古生物学与保护科学相结合，直接为生态系统恢复工作提供信息。从这项研究中获得的经验教训将广泛适用于岛屿和大陆上的物种入侵。研究人员挖掘了一个从现代一直延伸到晚更新世-全新世过渡时期的洞穴沉积物，这一时期因气候变化和巨型动物灭绝而闻名全球。这些化石记录提供了物种在进化过程中相互作用的生态快照。利用地层学和放射性碳定年法，研究人员将为化石遗骸建立一个时间框架，描述哪些哺乳动物物种在过去的哪个时期出现。这种年表允许研究人员测试物种如何随时间对环境和人为干扰作出反应的生态假设。利用碳和氮的稳定同位素可以重建食物网、物种相互作用和资源利用的变化。通过应用这些同位素，研究人员将评估每种本地物种在灭绝和入侵事件下的营养位置和生态位宽度，从而测试诸如竞争性释放和生态位收缩等广泛的生态概念。他们还将评估长期以来的假设，即入侵物种在其入侵的生态系统中相对于本地物种具有更宽的生态位宽度。

The highways and shipping routes that crisscross our planet are eroding the boundaries that once separated biological communities by introducing non-native species. These invasive species have come at an economic and ecological cost for the US, harming agriculture, fisheries, and our iconic landscapes. On islands, these invaders are even more detrimental, often competing with or eating native species to the brink of extinction and thus irreversibly damaging biodiversity hotspots. In this project, researchers will take an innovative approach to understand the consequences of invasive species by combining data from 15,000-year-old fossils and modern specimens alike. Using fossils excavated in the Dominican Republic, researchers will reconstruct the ecological interactions of native mammal species (such as sloths, monkeys, and rodents) before and after the arrival of prehistoric humans (6,000 years ago), as well as after the arrival of Europeans (500 years ago) and the invasive species that accompanied them. A baseline of how native species respond to extinction will provide context for understanding where invasive species fit within the modern ecosystem. For example, do invasive herbivores such as goats consume vegetation similar to what was consumed by extinct native sloths? This research integrates paleontology with conservation science to directly inform ecosystem restoration efforts. The lessons learned from this research will be broadly applicable to species invasions on islands and continents alike. The researchers excavated a cave deposit extending from the modern day back across the Late Pleistocene-Holocene transition, a period known globally for climatic changes and megafaunal extinctions. This fossil record provides ecological snapshots of species interactions through evolutionary time. Using stratigraphic layers and radiocarbon dating, the researchers will establish a temporal framework for the fossil remains, describing which mammalian species were present at what time periods in the past. This chronology permits researchers to test ecological hypotheses of how species respond to environmental and anthropogenic perturbations through time. Food webs, species interactions, and changes in resource use can be reconstructed using stable isotopes of carbon and nitrogen. Through applying these isotopes, researchers will assess the trophic position and niche breadth of each native species in response to extinction and invasion events, thereby testing broad ecological concepts such as competitive release and niche contraction. They will also evaluate the longstanding assumption that invasive species have wider niche breadths relative to native species in the ecosystems they invade.