Global biogeography of Albian ammonoids: A network-based approach

Abstract

Large-scale biogeographic provinces of Cretaceous ammonoids, as currently defined in the literature, were delimited using qualitative assessments of taxonomic inventories. Using aggregated species occurrences in the Paleobiology Database, we generated a geographic network to quantify connectivity of Albian epicontinental basins and used the flow-based Infomap algorithm to delineate bioprovinces. Despite taxonomic, stratigraphic, and geographic limitations of the data, the Infomap bioprovinces are largely concordant with the traditional, qualitatively derived biogeographic model, including the Boreal-Pacific Subrealm, Arctic Subrealm, Tethyan Realm, and Austral Realm. An agglomerative hierarchical cluster analysis applied to the same occurrence data failed to replicate the Infomap bioprovinces or reproduce the traditional qualitative model. The observed asymmetrical distribution of the Infomap bioprovinces is consistent with the known hemispheric differences in paleogeographic and oceanographic features of the Albian Earth. The geographic network derived from ammonoid data is twice as dense as the one derived for Albian benthic marine invertebrates and thus more effective in delineating global biogeographic units. The network-based approach establishes a reproducible quantitative framework for delineating geographic boundaries of marine bioprovinces, tracking biogeographic changes over evolutionary time scales, and identifying biotic and abiotic factors that influence global partitioning of marine biodiversity.