Diverse Fossil Floras from the Paleogene of Patagonia, Argentina: Origins of High Plant and Insect Diversity in South America

0345750野生动物热带南美洲拥有世界上最丰富的陆生植物和动物种群，使该地区成为保护的重中之重。然而，由于南美洲北部的岩石暴露受到森林覆盖和深层风化的限制，人们对这种特殊的生物多样性的历史知之甚少。巴塔哥尼亚中纬度地区的古新世和始新世早期植物群化石是解决这一问题的宝贵资源。这些组合充分暴露在现代沙漠露头中，代表了在全球变暖时期存在的扩展的新热带森林南缘的湿润亚热带植被。最壮观的巴塔哥尼亚植物群之一来自拉古纳德尔亨科（LH），这是阿根廷Chubut省的一个始新世早期（5200万年前）遗址，保存完好，与最著名的北美始新世植物群一样，如弗洛里桑特和共和国。在早期的努力中，研究人员从不到5000个标本中恢复了155多个植物物种。这些实体中只有不到25%以前是已知的。根据样本量调整后，这大大超过了其他地区始新世植物区系的丰富程度，但仍有可能发现更多的物种。在这些化石植物上，保存完好的新生代植物群中，昆虫介导的叶片损害的多样性最高，包括各种以前未记录的专门取食的例子，如瘿虫和矿虫。这些早期的结果支持了一种假设，即南美的高度多样性，通常被认为是最近200万到1000万年间发生的相对较近的事件，可能有相当古老的历史。本研究将研究LH和另外两个植物区系，一个始新世区系（里约热内卢Pichileufu，里约热内卢Negro省）和一个古新世区系（Salamanca， Chubut省）的植物多样性、植物和昆虫系统学以及植物-昆虫关联。要解决的主要问题包括：(1)在古近纪巴塔哥尼亚的广大地区是否存在高度的植物和昆虫取食多样性？(2)在全球变暖的古新世到始新世，植物和昆虫的多样性是否与世界其他地区一样？(3)这些植物群和它们的昆虫食草动物的确切的新热带和“澳大拉西亚”亲缘关系是什么？这些亲缘关系对理解现代生物群的重要性是什么？预计这项工作将在学生培训、国际合作和成果传播方面产生若干有益影响。学生的参与将是研究从实地到发表的所有阶段的核心，包括两名女性和一名男性阿根廷博士生的主要参与。该项目是在阿根廷科学机会减少的情况下，美国和阿根廷不同专家之间的国际合作。主要的库存数据将通过专题处理、数据集的互联网出版和在阿根廷宿主储存库存放标本的方式永久提供给研究界。对南美洲生物多样性的深刻历史的揭示预计将对今天南美洲的研究和保护工作产生影响。

0345750WilfTropical South America has the highest species richness in the world for many groups of terrestrial plants and animals, making this region a top priority for conservation. However, the history of this exceptional biodiversity is poorly understood because rock exposures in northern South America are limited by forest cover and deep weathering. Paleocene and early Eocene fossil floras from middle latitudes of Patagonia are invaluable resources for addressing this problem. Well exposed in modern desert outcrops, these assemblages represent humid subtropical vegetation from the southern reaches of the expanded Neotropical forests that existed during a globally warm time period. One of the most spectacular Patagonian floras comes from Laguna del Hunco (LH), an early Eocene (52 million years ago) site in Chubut Province, Argentina with outstanding preservation equal to the most famous North American Eocene floras, such as Florissant and Republic. In earlier efforts, the investigators recovered more than 155 plant species from fewer than 5,000 specimens. Fewer than 25% of these entities were previously known. Adjusted for sample size, this significantly exceeds the richness of Eocene floras from any other region, yet the potential exists for many more species to be found. On these fossil plants is preserved the highest diversity of well-preserved, insect-mediated leaf damage of any Cenozoic flora, including diverse and previously unrecorded examples of specialized feeding such as galls and mines. These early results support the hypothesis that South American hyperdiversity, usually attributed to relatively recent events of the last 2-10 million years, may have a considerably more ancient history. This study will examine floral diversity, plant and insect systematics, and plant-insect associations at LH and two other floras, one Eocene (Rio Pichileufu, Rio Negro Province) and one Paleocene (Salamanca, Chubut Province). Major questions to be addressed include: (1) Did high plant and insect-feeding diversity exist over a broad area of Paleogene Patagonia? (2) Was there a diversification of plants and insects from the Paleocene to the Eocene with global warming as seen elsewhere in the world? (3) What are the precise Neotropical and "Australasian" affinities of the floras and their insect herbivores, and what is the importance of these affinities for understanding modern biotas? The work is expected to have several beneficial impacts with regard to student training, international collaboration, and dissemination of results. Student participation will be central to all phases of the research from field to publication, including the major involvement of two female and one male Argentine doctoral students. The project is an international collaboration among diverse U.S. and Argentine specialists at a time of reduced scientific opportunity in Argentina. Primary inventory data will be permanently available to the research community through monographic treatments, Internet publication of data sets, and the deposition of specimens in the Argentine host repository. Illumination of the deep history of South American biodiversity is expected to have impacts on research and conservation efforts in South America today.