Oct. 24-26, 2009, Yingjie Overseas Exchange Center, Peking University, Beijing, China中文版

The Great Ordovician Biodiversification Event (GOBE):  causes and consequences of diversity’s big bang

David A.T. Harper (DHarper@snm.ku.dk)

Natural History Museum of Denmark (Geological Museum), University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark

The Ordovician Period (c. 488-444 Ma) witnessed the steepest rise in the biodiversity and biocomplexity of marine life during the Phanerozoic, marked by the installation of a benthos dominated by suspension-feeding animals. These changes in the abundance of life associated with increased bioturbation and tiering structures, set the agenda for subsequent marine ecosystems on the planet. Whereas the Cambrian Explosion generated a range of spectacular new body plans, it was not until some 20 Myr later that biodiversity at the family, genus and species level began to climb. Over an interval of some 25 Myr, accelerating γ (inter-provincial), β (inter-community), and α (intra-community) diversities were initiated by high diversities amongst Early Ordovician benthic faunas, emerging from the widespread anoxia of the Furongian (late Cambrian), and associated with the dispersal of the continents and the high frequency of volcanic arcs and microcontinents (γ diversity) against a background of sustained sea level rise during warm climates.  For example, the disparate and diverse assemblages belonging to the Celtic, peri-Gondwanan and Toquima-Table Head, peri-Laurentian marginal and oceanic provinces helped accelerate the event, providing geographic centres for speciation. Moreover, during the Early and Mid Ordovician, community types expanded particularly into deeper water and around carbonate platforms and within mound structures (β diversity) and more animals were squeezed into communities by the canalization of ecological niches permitting more diverse and densely packed associations (α diversity). Other factors such as an abundance of phyto and zooplankton and planktotrophic larvae, driving a plankton revolution together with periodic meteorite showers, fluctuations in the planet’s climate and water temperature associated with sea-level changes may have provided critical resources and stimuli to a rapidly diversifying marine invertebrate fauna, participating in new trophic structures that reached its Palaeozoic plateau during the Late Ordovician. Recent standardized curves for Phanerozoic diversity indicate that the peak of the Ordovician radiation was rarely exceeded during subsequent geological time, highlighting the GOBE as one of a handful of truly major biological events.

David A.T. Harper

University of Copenhagen, Denmark

Biography

David Harper is Professor of Palaeontology, University of Copenhagen and is in charge of the palaeontological collections in the Geology Department, Natural History Museum of Denmark, University of Copenhagen. He is also head of the Geology Research Group at the museum. His research is field and specimen-based, focussed on the Lower Palaeozoic rocks and fossils of Greenland, Scandinavia, the British Isles and China and together with the Cenozoic of the Caribbean basin and he has an interest in developing computer-based methodologies for the analysis of fossils and their distributions, for example the computer software PAST. He has published some 250 scientific papers and over ten books. He is a past editor, Vice President and Chair of the Publications Board of the Palaeontological Association and is currently President of the International Palaeontological Association and Chairman of the International Subcommission on the Ordovician System.