RUI: From Greenhouse to Icehouse: Documenting evolutionary trends in freshwater siliceous organisms over 80 million years of environmental change

在地质时期，全球气温从暖到冷以及从冷到暖的变化影响了物种的进化和灭绝，并导致了全球范围内生态系统的大规模重组。最近一次从温室到现在的冰窖的转变开始于5500万年前，与大气中二氧化碳的减少同时发生。该项目的目的是利用化石记录来研究从温室到冰窖条件转变过程中选定的淡水生物的进化趋势。该项目将为了解全球变暖条件下，特别是北纬地区的淡水生态系统是什么样子，以及它们如何应对降温奠定基础。这将为理解未来气候变暖情景下生态系统的响应提供一个框架。该项目将推进目标谱系的进化知识，发现新物种，检查最古老的淡水硅藻栖息地，为将生命之树的组成部分校准为地质时间提供特定时间的标记，并提高博物馆标本的价值。该项目将提供本科生研究实习机会，并通过图书馆和老年中心的演讲为公众提供教育机会。该项目的目标是通过记录从晚白垩纪到中新世跨越8000万年的物种，扩大对北美淡水化石共生植物、chrysophytes、硅藻、真形虫、heliozoans和海绵的认识。微化石将被记录在来自9个地方的几百个样本中，并与文献和博物馆记录中的历史信息合并，形成一个数据库，以检验关于进化史的特定假设。这组化石地点将产生大量的新物种，反过来，将促进对生物多样性、生物地理学和所有生物在从温室到冰窖地球过渡的关键时期的形态特征进化的理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over geologic time, shifts in global temperatures from warm to cold and vice versa have influenced the evolution and extinction of species, and caused large-scale reorganizations of ecosystems worldwide. The latest swing from Greenhouse to the current Icehouse began over 55 million years ago, concurrent with declines in atmospheric carbon dioxide. The objective of this project is to use the fossil record to examine the evolutionary trends of selected freshwater organisms during the shift from Greenhouse to Icehouse conditions. The project will build a foundation for understanding what freshwater ecosystems were like under globally warm conditions, especially in northern latitudes, and how they responded to cooling temperatures. This will provide a framework for understanding ecosystem responses under future climate warming scenarios. The project will advance evolutionary knowledge of the target lineages, uncover new species, examine the oldest localities harboring freshwater diatoms, provide time-specific markers for calibrating components of the Tree of Life to geologic time, and enhance the value of museum specimens. The project will provide undergraduate research internships, and educational opportunities for the general public through presentations at libraries and senior centers.The goal of this project is to expand knowledge of North American freshwater fossil synurophytes, chrysophytes, diatoms, euglyphids, heliozoans and sponges through documentation of species spanning 80 million years from the Late Cretaceous through the Miocene. Microfossils will be documented in several hundred samples from nine localities, and merged with historical information from the literature and museum records to assemble a database to test specific hypotheses on evolutionary history. The suite of fossil localities will yield an abundance of new species that, in turn, will advance an understanding of biodiversity, biogeography, and evolution of morphological traits for all of the organisms over a critical time period spanning the transition from a Greenhouse to Icehouse Earth.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.