CAREER: Tracking the evolution of grasses and grasslands: using phytoliths to explore evolution-ecology links in deep time

职业：追踪草和草原的进化：利用植硅体探索深层进化与生态学的联系

• 批准号: 1253713
• 负责人: Caroline Stromberg
• 金额: $ 52.5万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-06-01 至 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1253713&HistoricalAwards=false
• 关键词: CAREER; Tracking; evolution; grasses; grasslands

CAREER: Tracking the evolution of grasses and grasslands: using phytoliths to explore evolution-ecology links in deep timeCaroline Stromberg, University of WashingtonGrasslands cover 40% of Earth's land surface today, provide habitats for over a billion animals including humans, and greatly influence global climate and the carbon and silica cycles. Understanding the history of the grassland biome is essential for disentangling its complex controls and predicting how natural grasslands and crop plants will respond to ongoing human induced climate change. In recent years, analysis of fossilized plant silica (phytoliths) has shed much needed light on evolutionary and ecological events during the establishment of grasslands. However, gaining further knowledge depends critically on refined methods for identifying specific grass lineages in the fossil record. This CAREER research has two main goals. First, the project will enhance the use of phytoliths for robust taxonomic (the naming of species) and ecological interpretations through the first comprehensive and detailed mapping of grass phytolith shapes in an evolutionary framework, coupled with mapping of other, functionally relevant traits (e.g., photosynthetic pathway) and environmental preferences. Second, project will use this "key" to fossil grass types and ecology to tackle two outstanding questions in grass evolution: (1) When and in what environments did grasses originate and diversify?; and (2) What drove the ecological expansion of grasses with C4 photosynthesis? To address the first question, the project will study Cretaceous-Paleogene (145-23 million years ago) phytolith assemblages from Argentina to determine the evolutionary relationships between the grasses present, and use this information to determine when the lineage split occurred. Phytolith assemblage analysis and other paleobotanical evidence will help determine what early grass habitats were like. To address the second question, the project will analyze Miocene-Pliocene (23-2.6 million years ago) phytolith assemblages from Kansas to document the ecological expansion of C4 grasses in the Great Plains. The project will infer major C4 grass lineages present, and reconstruct changes in vegetation structure. Direct comparison with stable isotopic data from the section will permit testing of which factors influenced the rise to dominance of C4 grasses. The results of this research program will transform the study of ecosystem change during the last ~70 million years, specifically the assembly of grasslands, and allow evaluation of what processes control grassland evolution, in the past and in the future. It will also contribute fundamentally to archaeology, where phytoliths have long been a principal tool for tracking domestication of crop plants and land use. The integrated themes explored in this research program--evolution, ecology, and environmental change--will be incorporated into formal and informal education at the middle-school- to graduate-school-level and public outreach. This educational component will be accomplished through (1) inquiry-based labs and activities in my undergraduate courses at University of Washington, (2) research mentoring of one postdoctoral researcher, one graduate student, and at least 7 undergraduates in the lab and field, (3) design of new exhibits at the Burke Museum demonstrating evolution research in action, and (4) an after-school program aiming to engage middle-school girls, which remain minorities in STEM, in evolution-ecology science. The joint research and educational activities proposed here aim to inspire a greater appreciation for the processes that shaped and continue to shape our world, and more broadly, a better understanding of the practice of science and critical thinking in students of all ages.

职业：追踪草和草原的进化：利用植硅体探索深层进化与生态之间的联系卡罗琳·斯特罗姆伯格，华盛顿大学如今草原覆盖了地球陆地表面的 40%，为包括人类在内的超过 10 亿动物提供了栖息地，并极大地影响了全球气候以及碳和二氧化硅循环。了解草原生物群落的历史对于理清其复杂的控制并预测天然草原和农作物将如何应对持续的人类引起的气候变化至关重要。近年来，对植物硅化石（植硅体）的分析为了解草原形成过程中的进化和生态事件提供了急需的线索。然而，获得进一步的知识关键取决于识别化石记录中特定草谱系的精确方法。这项职业研究有两个主要目标。首先，该项目将通过在进化框架中首次全面详细地绘制草植硅体形状图，并结合其他功能相关性状（例如，光合作用途径）和环境偏好。其次，项目将利用这把化石草类型和生态学的“钥匙”来解决草进化中的两个突出问题：（1）草何时、在什么环境中起源并多样化？ (2) 是什么推动了具有C4光合作用的草类的生态扩张？为了解决第一个问题，该项目将研究来自阿根廷的白垩纪-古近纪（145-2300万年前）植硅体组合，以确定现有草类之间的进化关系，并利用这些信息来确定谱系分裂发生的时间。植硅体组合分析和其他古植物学证据将有助于确定早期草丛的栖息地是什么样的。为了解决第二个问题，该项目将分析堪萨斯州的中新世-上新世（23-260 万年前）植硅体组合，以记录大平原 C4 草的生态扩张。该项目将推断存在的主要 C4 草谱系，并重建植被结构的变化。与该剖面的稳定同位素数据进行直接比较将有助于测试哪些因素影响了 C4 草的优势地位。该研究计划的结果将改变对过去约 7000 万年生态系统变化（特别是草原聚集）的研究，并允许评估过去和未来控制草原演化的过程。它还将为考古学做出根本性贡献，长期以来，植硅体一直是追踪农作物驯化和土地利用的主要工具。该研究计划探索的综合主题——进化、生态和环境变化——将被纳入初中到研究生阶段的正式和非正式教育以及公共宣传中。这一教育部分将通过以下方式完成：(1) 在华盛顿大学的本科课程中进行基于探究的实验室和活动，(2) 对实验室和现场的一名博士后研究员、一名研究生和至少 7 名本科生进行研究指导， (3) 在伯克博物馆设计新展品，展示进化研究的实际应用；(4) 一项课后项目，旨在让中学生（在 STEM 领域仍属于少数）参与进化生态科学。这里提出的联合研究和教育活动旨在激发人们对塑造并继续塑造我们世界的过程有更多的认识，更广泛地说，更好地理解各年龄段学生的科学实践和批判性思维。