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Thirty-five paleobiologists met in May 1987 to reassert Darwin's metaphor in an examination of the evolution of terrestrial ecosystems. We did so with enthusiasm and confidence; the conference was successful. Although the theme was general-to examine the roles of history and of process in ecosystem development-the conferees focused on a more specific agenda: on concepts and principles for taphonomic and ecologic analysis, and on the major transformations in ecosystem structure and dynamics. The meeting was organized by Kay Behrensmeyer, Bill DiMichele, Dick Potts, and Scott Wing from the Paleobiology Department of the National Museum of Natural History, and was supported by the Smithsonian Institution through the Evolution of Terrestrial Ecosystems Program. The participants were secluded at Arlie House, 50 miles west of Washington, D.C., from May 15-19 to eat and dream ecosystem evolution as well as discuss it. Their interests ranged from sedimentology and taphonomy through paleobotany, paleoentomology, and vertebrate paleontology to feeding guilds, ecological energetics, and evolutionary ecology; their ideologies ranged from data-base development to ecological and evolutionary theory. The conference was organized around five working groups with overlapping membership: three focused on time intervals (Paleozoic, Mesozoic/Paleogene, and Neogene/Pleistocene), and two examined topics (taxon-free characterization of assemblages and paleoenvironmental analysis/taphonomy). Given the ideological tensions among observers, analysts, and synthesizers, and the differences in professional focus as well as the inherent differences among their assignments, each working group evolved its own approach and product with distinct divergence as well as parallelism and convergence. The organizers charged the paleoenvironments/taphonomy group with identification of the paleoenvironments whence the evidence of ancient ecosystems has come, and with assessment of the sampling of environments and ecosystems through time. The first two sessions were frustrating to many as they involved educating the uninitiated and tended to drift into nitty-gritty details. In the final session, however, these problems were partly resolved in the production of a chart-like outline of paleoenvironments into which were inserted observations on taphonomy of plants, animals, and trace fossils. The group thus dealt with environmental identification and with sampling within environments but failed to resolve questions about inter-habitat and temporal biases in sampling. The working group on taxon-free characterization of assemblages had its own successes and failures. Perhaps because of the scarcity of generalists amidst the taxonomic, morphologic, and ecologic specialists, discussion emphasized identification of the ecomorphotypes within particular groups of terrestrial organisms, the vascular plants, the "lower" tetrapods (amphibians and reptiles), and the mammals. The paleobotanists produced a happy synthesis for vascular plants using characteristics that defined their predominate roles in ecosystems. The paleomammalogists attempted a microclassification of adaptive zones and niches. Those interested in lower tetrapods developed a simpler categorization in terms of body size, activity levels, and general feeding habits. Features other than morphologic such as occurrence, abundance, and population structure received only passing mention despite their significance in reconstruction of ecosystem dynamics. The time-interval working groups followed diverse pathways to a wide range of results. The Paleozoic working group, after reviewing the evidence for ecosystem development in that interval, focused on the development of plant associations of modern aspect in relation to the deployment of terrestrial herbivores. Members of the group agreed that large-scale herbivory was clearly a late development, for detritivory was the dominant feeding mode for invertebrates as late as the end of the Carboniferous, and herbivory wasn't important for vertebrates until late Permian. This pattern is probably explicable in terms of the productivity and architecture of Paleozoic plants, but the working group conceded that a more precise and reliable synthesis and more robust explanation will require additional informa |
