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Content archived on 2024-05-29

Patterns and processes of species diversification after mass extinctions: A case study on Triassic Pectinoidea (Mollusca, Bivalvia)


A comprehensive survey of all Triassic pectinoid bivalves (`scallops) will allow for the first time an analysis of patterns and processes of global biodiversification at the species level. Triassic pectinoids are particularly suitable to reveal general ins ights into biodiversification processes, because the end-Permian mass extinction event left members of this superfamily nearly unaffected, whereas their most important competitors (brachiopods) suffered dramatically. This unique historical background allow s us to study how global diversification of a major group of marine invertebrates proceeded in the virtual absence of competition, and how (re)establishment of interacting groups influenced the diversification patterns and processes later. For this purpose , species diversity plots of Triassic pectinoids will be constructed and corrected for rock volume and sampling bias. Exponential and logistic curves will then be fitted to these plots and analysed in terms of their statistical significance and biological meaning. Overall shape of the diversity curves and the nature of their best fits (i.e. logistic or exponential) will be used to test rival concepts of biodiversification including underlying assumptions about the relative importance of competition, predat ion, positive biotic interaction, newly evolved adaptations, and intrinsic rates of diversification and equilibrium diversities. A crucial question particularly in testing equilibrium versus non-equilibrium models will be whether the end-Permian extinction event was followed by initial hyperexponential bursts into the largely vacated ecosystems, or rather by slowly accelerating biodiversification, indicating a central role for positive feedback processes. The results obtained for Triassic pectinoids are exp ected to be paradigmatic for marine biodiversification in general, and will significantly advance the development of data-based concepts of biodiversification.

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