Long & Medium Term Research: Paleobotanical Patterns in theEvolution of Angiosperm Secondary Xylem & Their PhylogeneticSignificance

中长期研究：被子植物次生木质部演化的古植物学模式及其系统发育意义。该奖项是在国外卓越中心长期和中期研究计划下推荐的。该项目旨在使美国科学家和工程师能够在国外被证明卓越的研究机构进行长期研究。该奖项为开展联合研究以及利用国外独特或互补的设施、专业知识和实验条件提供了机会。该奖项将支持Patrick S. Herendeen博士对瑞典斯德哥尔摩进行为期12个月的访问，与瑞典自然历史博物馆的Else Marie Friis教授一起研究“被子植物次生木质部的进化模式及其系统发育意义”。对北美洲和欧洲白垩纪（巴雷米亚-塞诺曼）保存完好的fusainized （charcoalified）被子植物木材化石进行研究，以评估早期被子植物次生木质部的结构演化模式。在白垩纪中期，被子植物经历了最初的主要多样化，因此本研究的数据将为基于现有分类群的木材进化假说的比较提供历史视角。研究人员将利用从美国东部和葡萄牙中部收集的大量材料，作为已经在进行的国际合作项目的一部分，研究早期被子植物的化石花和其他生殖结构，瑞典博物馆已经对其中的大部分进行了筛选、清洗，并准备进行研究。由于初步结果表明，这些收藏品很容易提供详细的解剖数据，因此建议的项目可以在一年内完成。首席研究员将用扫描电镜检查并量化许多被认为具有进化或生态重要性的解剖特征。计算机化的多重输入键将有助于确定这些化石的系统亲缘关系。生殖结构附着在树枝或花序轴上也有助于识别某些木材类型。首席研究员将通过比较在被子植物木材中观察到的进化变化模式与在同一地点的树叶、花粉和生殖结构化石中观察到的进化变化模式，来评估早期被子植物中马赛克进化的意义。他将通过比较被子植物木材与共生裸子植物木材和其他被子植物遗骸的数据，来区分进化变化的模式和生态因素的变化。

Long & Medium-Term Research: Paleobotanical Patterns in the Evolution of Angiosperm Secondary Xylem and Their Phylogenetic Significance. This award recommendation is made under the Program for Long & Medium-Term Research at Foreign Centers of Excellence. The program seeks to enable U.S. scientists and engineers to conduct long-term research abroad at research institutions of proven excellence. Awards provide opportunities for the conduct of joint research, and the use of unique or comple- mentary facilities, expertise and experimental conditions in foreign countries. This award will support a twelve-month visit by Dr. Patrick S. Herendeen to Stockholm, Sweden, to work with Professor Else Marie Friis at the Swedish Museum of Natural History on "Patterns in the Evolution of Angiosperm Secondary Xylem and Their Phylogenetic Significance," an investigation of well- preserved fusainized (charcoalified) fossil angiosperm wood from the Cretaceous (Barremian-Cenomanian) of North America and Europe to assess patterns of structural evolution in the secondary xylem of early angiosperms. Through the mid- Cretaceous, angiosperms underwent their initial major diversification, so data from this study will provide a historical perspective against which to compare hypotheses of wood evolution based on extant taxa. The researchers will use abundant material collected from eastern USA and central Portugal as part of an international cooperative project already underway to study fossil flowers and other reproductive structures of early angiosperms, much of which the Swedish Museum has sieved, cleaned, and made ready for study. Because preliminary results indicate that these collections readily provide detailed anatomical data, the proposed project can be completed within one year. The principal investigator will examine with the SEM and quantify numerous anatomical features thought to be of evolutionary or ecological importance. A computerized multiple entry key will facilitate determining of systematic affinities for these fossils. Attachments of reproductive structures to branches or infructescence axes may also assist in identifying some wood types. The principal investigator will assess the significance of mosaic evolution among early angiosperms by comparing patterns of evolutionary change observed in angiosperm wood with those observed in fossil leaves, pollen and reproductive structures at the same localities. He will distinguish patterns of evolutionary change from changes due to ecological factors by comparing data on angiosperm wood with that for co-occurring gymnosperm wood and other angiosperm remains.