Evolutionary patterns in the dinoflagellate cyst genus Spiniferites (Cretaceous through Quaternary): Relationships to sea-level changes
Titel:
Evolutionary patterns in the dinoflagellate cyst genus Spiniferites (Cretaceous through Quaternary): Relationships to sea-level changes
Auteur:
Hultberg, Stefan U. Malmgren, Bjorn A.
Verschenen in:
Historical biology
Paginering:
Jaargang 10 (1995) nr. 4 pagina's 341-357
Jaar:
1995-11
Inhoud:
The dinoflagellate cyst genus Spiniferites is one of the most geographically widespread and stratigraphically long-ranging dinocyst genera. Rates of taxonomic evolution in this genus from its appearance in the Early Cretaceous to the present day (rates of speciation and extinction, net diversification, evolutionary turnover rate, and standard diversity) have been analyzed. The rate of speciation was high during the early stages of evolution of Spiniferites in the Early Cretaceous, remained relatively stable from the Aptian to Oligocene, and increased again in the Pliocene and Pleistocene. In the initial evolutionary stages the number of speciations exceeded the number of extinctions, but once an equilibrium stage had been reached they are generally of a similar magnitude. Enhanced extinction rates, however, occurred in the Eocene and Pliocene-Pleistocene. The net diversification rate (number of speciations-number of extinctions) was high in the Early Cretaceous, reflecting the rapid initial diversification phase. The diversification rate was relatively stable from the Albian to Recent, with episodes of net extinctions in the Albian, Maastrichtian, and Eocene. The standing diversity, measured using the Harper index, follows closely the observations and predictions by Sepkoski's deterministic model: initial rapid diversification followed by a steady-state system. Macroevolutionary patterns in Spiniferites may be linked to sea-level change through the mediating influence of various possible physical agents. Periods of both extreme high- and lowstands of sea-level appear to exert evolutionary pressure on Spiniferites. The observation that rapid evolutionary turnover is coupled to extreme sea-level stands supports the Stationary Evolutionary hypothesis rather than the Red Queen hypothesis.
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