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：南美洲的草地生物群是如何演变的？整合巴塔哥尼亚、阿根廷、科恩和马登皮斯草原的新生代气候、花卉和动物记录，这些草原今天占地球的1/4？的植被覆盖，被认为是在南美洲发展早于其他大陆，根据植物，动物群和沉积学证据在格兰巴兰卡，阿根廷，和附近。 然而，变化的时间和速度以及因果机制仍然不清楚。我们将确定与地球演化有关的气候、植被和动物事件的时间和性质。的最早的草原生态系统在阿根廷南部的植物，稳定同位素，和动物区系的数据，通过长期的，良好的日期，几乎连续的沉积记录在Gran Barranca（~42.0 ~~18.5 Ma）。我们将重点评估是否：（1）在南美洲，开放生境草的优势地位的上升与它们的出现平行，（2）生境开放性的增加与开放生境草的生态优势地位的上升平行，（3）植被的变化与气候变化相关，（4）南美食草哺乳动物的高齿类对开阔的、以草为主的栖息地的扩张反应迅速。将分析化石植硅石（植物硅），以提供草以及其他气候或生态敏感植物群（例如，棕榈、莎草）。将分析化石牙齿的稳定同位素组成，重点是散装d13 C值和d13 C和18 O值的同位素分区。连同植硅体组合数据和沉积学，这种同位素信息将被用来推断栖息地的开放性，干燥度和季节性的温度和降水的变化。与记录的动物群落组成和功能形态的比较将阐明草地扩张和动物区系响应的模式。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)南美洲的动物群-植物群-气候演变模式与后来发生的类似变化相比如何，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途径，包括博物馆内展览，草原演变旅行学习包材料，以及通过博物馆网站在线访问图像的植硅石数据库的开发。

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.