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：南美洲草原生物群是如何演化的？：整合了巴塔哥尼亚、阿尔根塔斯罗伯格、科恩和马登皮斯草原的新生代气候、动植物和动物群记录，这些草原今天构成了地球的四分之一？S植被覆盖被认为是南美洲比其他大陆更早形成的植被，基于阿根廷格兰巴兰卡及其附近的植物、动物群和沉积学证据。然而，变化的时间和速度以及因果机制仍不清楚。我们将通过Gran Barranca(~42.0 Ma至~18.5 Ma)长期、准确且几乎连续的沉积学记录，通过整合植物、稳定同位素和动物群数据，确定与地球-S阿根廷南部最早的草原生态系统演化有关的气候、植被和动物群事件的时间和性质。我们将重点评估：(1)南美洲开放栖息地牧草的出现是否与它们的出现同步，(2)栖息地开放度的增加与开放栖息地牧草生态优势度的上升平行，(3)植被的变化与气候变化有关，以及(4)南美洲哺乳动物食草动物的潜伏性对开放的、以草为主的栖息地的扩展做出了快速反应。将对植物化石(植物硅)进行分析，以提供详细、连续的草以及其他对气候或生态敏感的植物群(如棕榈树、莎草)的花卉记录。将分析化石牙齿的稳定同位素组成，重点是整体d13C值和d13C和18O值的同位素分区。结合植硅体组合数据和沉积学，这些同位素信息将被用来推断栖息地的开放性、干燥度和季节性在温度和降水量方面的变化。与动物群落组成和功能形态的记录进行比较，将有助于阐明草地扩展和动物群落响应的模式。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发生的假设上类似的变化相比如何，例如在北美中部？拟议的项目包括通过伯克博物馆向公众传播研究的几种方式，包括博物馆内展览，草原演变旅行学习包的材料，以及开发植硅体数据库，通过S博物馆网站在线访问图像。

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.