COLLABORATIVE RESEARCH: HOW DID THE GRASSLAND BIOME EVOLVE IN SOUTH AMERICA?: INTEGRATING CENOZOIC CLIMATE, FLORAL AND FAUNAL RECORDS FROM PATAGONIA, ARGENTINA

合作研究：南美洲草原生物群落是如何进化的？整合来自巴塔哥尼亚、阿根廷、斯特隆伯格、科恩和马登群岛的新生代气候、植物和动物记录。根据在阿根廷格兰巴兰卡及其附近的植物、动物和沉积学证据，人们认为植物覆盖在南美洲比在其他大陆发展得更早。然而，变化的时间和速度以及因果机制仍不清楚。我们将确定与地球进化有关的气候、植被和动物事件的时间和性质。通过对Gran Barranca （~42.0 ~ ~18.5 Ma）长时间、年代准确且几乎连续的沉积学记录，综合植物、稳定同位素和动物数据，研究了阿根廷南部最早的草地生态系统。我们将重点评估：(1)南美洲开阔生境禾本科植物的优势地位上升是否与它们的出现同步发生；(2)开阔生境的增加是否与开阔生境禾本科植物的生态优势地位上升同步发生；(3)植被变化是否与气候变化相关；(4)南美洲食草哺乳动物的退化是否对开阔生境草本科植物的扩张做出了快速反应。植物岩化石（植物硅）将被分析，以提供详细的、连续的草类植物记录，以及其他对气候或生态敏感的植物类群（如棕榈树、莎草）。对牙齿化石进行稳定同位素组成分析，重点研究d13C总体值和d13C、18O值的同位素分带。结合植物岩组合数据和沉积学，这些同位素信息将用于推断栖息地开放性、干旱性以及温度和降水的季节性变化。通过与动物群落组成和功能形态记录的比较，阐明了草原扩张和动物响应的模式。我们的数据还将有助于回答以下两个问题：(1)阿根廷气候变化的时间和速度与海洋记录相比如何？(2)南美洲的动植物气候演变模式与后来假定发生的类似变化（如北美中部）相比如何？拟议的项目包括通过伯克博物馆向公众传播研究的几种途径，包括博物馆内展览，关于草原演变的旅行研究工具包的材料，以及通过博物馆在线访问图像的植物岩数据库的开发？年代的网站。

COLLABORATIVE RESEARCH: HOW DID THE GRASSLAND BIOME EVOLVE IN SOUTH AMERICA?: INTEGRATING CENOZOIC CLIMATE, FLORAL AND FAUNAL RECORDS FROM PATAGONIA, ARGENTINASTROMBERG, KOHN AND MADDEN PISGrasslands, which today form ~1/4 of Earth?s vegetative cover, are thought to have developed earlier in South America than on other continents, based on floral, faunal, and sedimentological evidence at Gran Barranca, Argentina, and nearby. However, the timing and rate of change remain unclear, as well as causal mechanisms. We will determine the timing and nature of climatic, vegetational, and faunal events related to the evolution of Earth?s earliest grassland ecosystems in southern Argentina by integrating floral, stable isotopic, and faunal data through the long, well-dated, and nearly continuous sedimentological record at Gran Barranca (~42.0 to ~18.5 Ma). We will focus on evaluating whether: (1) The rise to dominance of open-habitat grasses in South America occurred in parallel with their appearance, (2) An increase in openness of habitats occurred in parallel with the rise to ecological dominance of open-habitat grasses, (3) Changes in vegetation were correlated with climate change, and (4) Hypsodonty in South American mammalian herbivores responded rapidly to the spread of open, grass-dominated habitats. Fossil phytoliths (plant silica) will be analyzed to provide detailed, continuous floral records of grasses as well as other climate- or ecology-sensitive plant groups (e.g., palms, sedges). Fossil teeth will be analyzed for stable isotope compositions, focusing on bulk d13C values and isotopic zoning of d13C and 18O values. Together with phytolith assemblage data and sedimentology, this isotopic information will be used to infer changes in habitat openness, aridity, and seasonality in terms of temperature and precipitation. Comparison with records of faunal community composition and functional morphology will elucidate the patterns of grassland expansion and faunal responses. Our data will additionally help answer the following two questions: (1) How does the timing and rate of climate change in Argentina compare with the marine record? (2) How do patterns of fauna-flora-climate evolution in South America compare with putatively similar changes that occurred later, e.g., in central North America? The proposed project incorporates several avenues for disseminating the research to the public through the Burke Museum, including an in-museum exhibit, materials for traveling study kits on the evolution of grasslands, and development of a phytolith database with images accessible on-line through the Museum?s website.