IRFP: Assessing the Role of Ecosystem Structure in Extinction Patterns During the Cretaceous-Paleocene Mass Extinction

Redman Cory M, Bryan TX

Investigators

Abstract

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Cory M. Redman to work with Dr. Craig Scott at the Royal Tyrrell Museum of Palaeontology in Alberta, Canada. The magnitude of the problems threatening modern ecosystems resembles those intervals of geological time associated with mass extinctions; for this reason the fossil record provides a critical role in understanding the responses of ecosystems to global-scale disruptions. However, most paleoecological mass extinction studies have focused on measuring the magnitude of extinction among various taxonomic groups or trying to identify the primary abiotic cause(s) of the extinction. The role of ecosystem structure in the propagation of or resistance to an extinction event has largely gone unstudied. The Cretaceous-Paleogene (K-Pg) mass extinction is one of the most infamous mass extinctions in Earth?s history, due to the demise of the dinosaurs. Despite the profusion of publications, considerable controversy remains on the stability or health of terrestrial ecosystems prior to the K-Pg event and the changes in ecosystem caused by the extinction. The objective of the research proposed here is to quantitatively characterize changes in terrestrial ecosystems' structure before and after the K-Pg extinction event, using whole assemblage, rank abundance curves (RACs) of vertebrates and pollen. RACs are an ecological technique used to visually and quantitatively describe how taxa in an ecosystem partition resources and convert these resources into abundances. Any change in abundance structure across the K-Pg boundary would indicate change(s) in the processes that are influencing the ecosystems. Ecological studies utilizing modern and fossil organisms have shown that species abundance distributions change as a result of the frequency and magnitude of perturbations. Ecosystems that have experienced frequent perturbations are typically dominated by a few species that have a wide habitat range or food preference (i.e., generalists). In contrast, ecosystems that have not experienced frequent perturbations typically have resources apportioned more evenly across a diverse array of species, each one having a very narrow habitat range or food preference (i.e., specialists). The rationale for conducting this study is to determine if latest Cretaceous terrestrial ecosystems were already under ecological stress prior to the K-Pg boundary by directly analyzing pre- and post- extinction ecosystems using organisms that occupy different trophic levels (i.e., vertebrates = primary & secondary consumers; pollen= primary producers).