MCZ Lunchtime Seminar

A Quantitative Review of Ordovician Diversification

Jared Richards
PhD Candidate
Ortega-Hernández Lab

The Great Ordovician Biodiversification Event (GOBE) embodies the most dramatic increase of marine biodiversity and escalation of macroecological complexity during the early Phanerozoic. Numerous palaeobiological studies have attempted to quantify the GOBE based on estimates of richness through time for various groups of marine organisms. However, these studies use data restricted to specific regions, clades, or employ disparate methodologies that preclude direct comparisons. To explore the general trends in reported richness, we collated 166 datasets from 65 publications to analyze temporally standardized rates of marine species biodiversity accumulation between the latest Cambrian and the entire Ordovician using an effect-size approach. When combined, the current literature indicates a statistically significant high rate of sustained species accumulation that can be traced from the late Cambrian until the Middle Ordovician, stabilization during the Late Ordovician, and then a precipitous decline during the Hirnantian. Studies of benthic and suspension-feeding organisms show high rates of biodiversity accumulation throughout most of the Ordovician. In contrast, studies of the diversification of nektonic, pelagic, and predatory/scavenger organisms suggest their radiations were restricted to the Early Ordovician. By synthesizing information for reported richness from the literature, we provide a complementary perspective on the general literature of the GOBE.