The 'Ediacara biota' and Ediacaran-Cambrian transition
The Ediacaran-Cambrian transition marks possibly the most important geobiological revolution of the past billion years, including both the Earth’s first biotic crisis of macroscopic eukaryotic life – the disappearance of the enigmatic ‘Ediacara biota’, and its most spectacular evolutionary radiation – the ‘Cambrian Explosion’. Understanding where the Ediacara biota fit in the animal tree of life, the cause(s) behind their extinction in the latest Ediacaran, and the role of this extinction in driving the subsequent Cambrian radiation is thus key to understanding the origins of the modern biosphere. Our lab group uses a wide variety of techniques including paleoecological analyses, taphonomic experiments, fluid dynamics modeling, and original fieldwork to study the paleobiology and -ecology of these mysterious organisms. We chase these fossils and the rocks that host them in South Africa, Namibia, Newfoundland, and the southwestern United States.
Biogeography and the spatial fabric of mass extinction events
A central goal of paleobiology is to understand the guiding principles shaping life on Earth. This includes understanding the causes and consequences of mass extinctions, from which lessons can be applied to mitigating the current biodiversity crisis. The fossil record thus has a crucial role to play in predicting and remediating the effects of ongoing defaunation and global change.
Mass extinctions are commonly studied in terms of the fall of major taxonomic groups (i.e., rates of species extinction). By contrast, little attention has been paid to the effects of mass extinction on the organization of biota in space (‘biogeography’), even though modern ecosystems show strong biogeographic changes in response to ecological stress. My research group is tackling this area in a variety of different ways. Most importantly, using the fossil record to interpret present-day changes in biogeographic patterns requires that we understand how faithfully the compositions of living communities, and the existing distributions of species, can be preserved in the rock record (e.g., Hull, Darroch & Erwin, 2015 in Nature). My group is investigating these processes both through developing new, computer-driven simulation techniques, and by performing experiments (‘live-dead studies’) in modern marine environments. We also study the spatial responses of biota to mass extinctions in the field, and at a variety of spatial scales - most notable in Anticosti Island, Quebec.
Testing the quality of the fossil record
A key part of interpreting the record of past ecosystems change (such as those that happen over mass extinctions) is understanding how faithfully the composition of living communities is translated into fossils. The most effective way of quantifying this is by studying the composition of living communities, and then comparing that with the composition of their corresponding ‘dead’ communities (the remains of bones, shells, etc.) that form the developing fossil record. These are referred to as ‘live-dead’ studies, and can be used to calibrate the fidelity of fossil accumulation, as well as how this fidelity changes in different environments (see Darroch, 2012 in Palaios).
Our research group is working towards understanding this transition from living to fossil communities, most recently on San Salvador, the Bahamas.