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

职业：跟踪草和草地的进化：利用植物岩来探索进化与生态学的深层联系卡罗琳·斯特伦伯格，华盛顿大学今天，草原覆盖了地球陆地表面的40%，为包括人类在内的10亿多动物提供了栖息地，并极大地影响了全球气候以及碳和硅循环。了解草原生物群系的历史对于解开其复杂的控制因素和预测天然草原和作物植物如何应对持续的人类引起的气候变化至关重要。近年来，对植物硅石化石的分析为揭示草原形成过程中的进化和生态事件提供了必要的线索。然而，获得进一步的知识主要取决于在化石记录中识别特定草系的精确方法。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和详细地绘制草植物岩形状，以及绘制其他功能相关特征（如光合作用途径）和环境偏好，加强植物岩在强大的分类学（物种命名）和生态学解释中的应用。其次，本项目将利用这把研究草化石类型和生态学的“钥匙”来解决草进化中两个突出的问题：(1)草是在什么时候、在什么环境下起源和多样化的；(2)是什么驱动了C4光合作用下草地的生态扩张？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（1.45亿至2300万年前）植物岩组合，以确定现有禾草之间的进化关系，并利用这些信息来确定谱系分裂发生的时间。植物岩组合分析和其他古植物学证据将有助于确定早期草的栖息地是什么样的。为了解决第二个问题，该项目将分析来自堪萨斯州的中新世-上新世（2300万至260万年前）植物岩组合，以记录C4草在大平原的生态扩张。该项目将推断目前主要的C4草系，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，可以检验哪些因素影响了C4禾本科植物的优势地位上升。该项目的研究成果将改变过去~ 7000万年生态系统变化的研究，特别是草原的聚集，并允许评估过去和未来哪些过程控制了草原的演变。它还将对考古学做出根本性的贡献，在考古学中，植物岩长期以来一直是追踪作物驯化和土地利用的主要工具。本研究项目探索的综合主题——进化、生态和环境变化——将被纳入中学到研究生院的正规和非正规教育以及公共宣传中。这一教育组成部分将通过(1)我在华盛顿大学本科课程中的探究性实验室和活动来完成，(2)在实验室和现场指导一名博士后研究员、一名研究生和至少7名本科生的研究，(3)在伯克博物馆设计展示实际进化研究的新展品，以及(4)一个旨在吸引中学女生的课外项目，她们仍然是STEM领域的少数群体。在进化生态学中。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的更多认识，并从更广泛的角度出发，更好地理解所有年龄段学生的科学实践和批判性思维。

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.