CENOZOIC CLIMATE REGIME DROVE SPATIAL PATTERNS IN SPECIATION AND DISPERSAL DYNAMICS OF PLANKTONIC FORAMINIFERA

Global marine ecosystems are currently experiencing the most significant environmental change of the past 66 million years. Investigating how speciation and extinction patterns responded to climatic changes in the geological past provides a benchmark for assessing potential negative impacts in the future.

The marine microfossil record of Cenozoic planktonic foraminifera is the most complete and phylogenetically resolved of any group of organisms available for study. As such, the novel planktonic foraminiferal occurrence database, Triton, is used to assess the biogeographic variability of this group through geological time, examining trends in speciation and extinction locales. It is found that palaeolatitudes of speciation and extinction varied with regard to the underlying global climate conditions of the time. The Greenhouse regime of the early Paleogene was dominated by extratropical speciation cradles which, as global temperature declined, were progressively complimented by lower latitude speciation. This tropical speciation cradle now acts as the primary marine cradle in the cooler climates of the Icehouse regime.

The global biogeographic patterns observed within this study reveal fundamental elements of marine macroevolutionary dynamics through geological time, suggesting that the location of taxon speciation and extinction is driven primary by the underlying global temperature. As anthropogenic forcing pushes global climate towards a state analogous to the Greenhouse world of the Paleogene, marine speciation and biodiversity dynamics will likely migrate to higher latitudes, altering future marine ecosystem function.