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

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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.