The species-area relationship in the Late Ordovician: a test using neutral theory

The fundamental biodiversity number, , should be positively correlated with province area. This correlation can be tested in the fossil record using relative abundance distributions from known provinces. Late Ordovician (443-458 Ma) strata of Laurentia are divided into four geochemically and biologically distinct regions, or provinces, corresponding roughly to the western United States and Canada, Appalachian Basin, Cincinnati Arch, and Upper Mississippi Valley. I use existing and newly obtained bed-level census data to test whether is positively correlated with area of these provinces. Results indicate a positive relationship, which suggests the influence of provincial area, among other factors, on diversity, highlighting the inherent link between diversity and abundance structure at local and regional scales. Since diversity at smaller spatial scales is an important component of global biodiversity, determining the nature of this relationship in the fossil record has implications for understanding the assemblage of global diversity throughout the Phanerozoic.