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Marine biogeographic regions emerge in both recent times and the geological past but their drivers are puzzling. Compared to terrestrial settings, groupings of species distributions are difficult to delineate in the modern ocean. However, despite inferior global coverage and data quantity, paleontologists have long argued that the fossil record provides ample evidence to discriminate between past faunal provinces. Previously, a ubiquitously applicable, objective method to define biogeographic structuring has been lacking. Yet, if we are to understand how the spatial organization of life responds to changes of environmental factors, a robust methodology is required that uses nothing else but taxon occurrence data.
By applying cluster recognition methods based on network theory, researchers confirmed that modern and the near past global ecosystem, conserved in the fossil record, feature highly similar biogeographic structures, based solely on data from OBIS and the Paleobiology Database. This congruence is remarkable, the authors note, given the known climatic variations of the past ten million years. It demonstrates not only the robustness of the methods to sampling effort and dataset characteristics, but also suggested the long-term stability of the forces that govern biogeographic patterns on a global scale. Freeing the definition of biogeographic units from abiotic information also allowed the assessment of the influencing environmental parameters, such as temperature, nutrient input or salinity, without circular reasoning. The authors concluded that the distribution of landmasses and seawater temperature heterogeneities are the main drivers of shallow marine benthic bioregionalization, the former providing longitudinal separation, and the latter providing latitudinal separation. The authors reproduced their results separately for several higher taxonomic groups, finding good agreement between them, and showcasing the flexibility of their approach.
Full reference: Kocsis, Á. T., Reddin, C. J., & Kiessling, W. (2018). The stability of coastal benthic biogeography over the last 10 million years. Global Ecology and Biogeography, 27(9), 1106–1120. https://doi.org/10.1111/geb.12771