East meets West: The contrasting contributions of David L. Dilcher and Jack A. Wolfe to Eocene systematic paleobotany in North America

Although DAVID DILCHER and JACK WOLFE were born on the same summer day (July 10, 1936) in Cedar Falls, Iowa, and Portland, Oregon, respectively, their contributions to paleobotany have been a study in contrasts. WOLFE, the architect of CLAMP, and DILCHER, who helped place angiosperin paleobotany within the context of plant systematics, have found their own innovative ways of documenting and interpreting the evolutionary history and paleoccology of the angiosperms. From the beginning, both DILCHER and WOLFE recognized that an understanding of regional geological processes was essential when determining both the kinds of questions and techniques used when studying Tertiary floras. DILCHER'S Eocene work has focused on the megathermal Claiborne Formation of the Mississippi Embayment, while WOLFE'S centered on the "upland" microthermal floras of the northwestern Okanogan Highlands. DILCHER and his students, working in the Eocene floras of the clay pits of Kentucky and Tennessee, described an extinct, dry vegetation of the Southeast that was dominated by Lauraceae, Fagaceae and Leguminosae. The exquisite preservation of these southeastern floras allowed for detailed pollen and cuticular studies that provided a high degree of taxonomic precision. In contrast, WOLFE turned his attention to floras of British Columbia and eastern Washington that are dominated temperate elements such as Betulaceae and Rosaceae in an upland environment. The ability to precisely date dramatic changes in these floras through radiometric means provided WOLFE with a database for leaf physiognomic studies and the development of CLAMP (Climate Leaf Analysis Multivariate Program). The contrasting contributions of DILCHER and WOLFE have played a significant role in the development of Tertiary North American paleobotany and its contribution to the understanding of fossil and extant floras.