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。该奖项的推荐是根据外国英才中心的长期和中期研究计划提出的。该计划旨在使美国科学家和工程师能够在国外被证明是优秀的研究机构进行长期研究。奖项提供了开展联合研究的机会，并利用外国独特或必要的设施、专门知识和实验条件。这一奖项将支持Patrick S.Herendeen博士对瑞典斯德哥尔摩为期12个月的访问，与瑞典自然历史博物馆的Else Marie Friis教授合作，研究被子植物次生木质部进化的模式及其系统发育意义，对北美和欧洲白垩纪(Barremian-Cenomania)保存完好的褐化(炭化)被子植物木材化石的调查，以评估早期被子植物次生木质部的结构进化模式。在白垩纪中期，被子植物经历了最初的主要多样化，因此这项研究的数据将提供一个历史视角，以比较基于现有分类群的木材进化假说。研究人员将使用从美国东部和葡萄牙中部收集的大量材料，作为已经在进行的研究早期被子植物化石花和其他生殖结构的国际合作项目的一部分，瑞典博物馆已经对其中大部分进行了筛选、清理，并准备进行研究。由于初步结果表明，这些收集很容易提供详细的解剖学数据，拟议的项目可以在一年内完成。首席研究人员将用扫描电子显微镜进行检查，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钥匙将有助于确定这些化石的系统亲缘关系。生殖结构与枝条或果轴的附着物也有助于识别某些木材类型。首席调查员将通过比较被子植物木材中观察到的进化变化模式与同一地点的化石叶片、花粉和生殖结构中观察到的进化变化模式，来评估早期被子植物之间的镶嵌进化的意义。他将通过比较被子植物木材和共同出现的裸子植物木材和其他被子植物遗骸的数据，区分进化变化的模式和生态因素造成的变化。

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.