Morphological change in response to mass extinction: a case study of Strophomenida (Brachiopoda) at the Late Ordovician
Open Access
- Author:
- Sclafani, Judith
- Graduate Program:
- Geosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 19, 2019
- Committee Members:
- Mark E Patzkowsky, Dissertation Advisor/Co-Advisor
Mark E Patzkowsky, Committee Chair/Co-Chair
Timothy Bralower, Committee Member
Peter Daniel Wilf, Committee Member
David Peter Hughes, Outside Member
Mark E Patzkowsky, Program Head/Chair - Keywords:
- Late Ordovician mass extinction
recovery
morphometrics
paleoecology
evolutionary history - Abstract:
- There have been five mass extinctions throughout the Phanerozoic, all of which were caused by catastrophic disruptions to the earth system and resulted in significant biotic upheaval. Anthropogenic climate change, combined with other human activities, is pushing Earth towards a possible sixth mass extinction. The fossil record of extinctions contains clues about what might happen to Earth’s biota in the near future. I focus on the Late Ordovician mass extinction, which is the first of the “big 5” mass extinctions and the second largest. It was caused by a rapid climate event that resulted in the growth of continental glaciers and a drop in sea level. The ecological effect of this extinction is less than might be expected given the amount of taxonomic loss. Studying the nuances of this pattern from an evolutionary and ecological perspective might yield insight into some of the more complex metrics of quantifying changing biodiversity. To achieve this, I quantify morphology of the brachiopod order Strophomenida. Morphology is a product of evolution and ecology, allowing for the analysis of both. Results indicate a morphologic bottleneck at the Late Ordovician mass extinction event. This observed restriction in morphologic variability occurs within one clade that originates during the Silurian recovery interval. Further exploration of the data indicates no clear ecological signature to the bottleneck. The complex relationship between ecology and evolutionary history highlights the need to employ both approaches to develop a more complete understanding of intervals of biotic change.