EAR-PF: Respiratory physiology and survivorship during the End-Permian Mass Extinction

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Dr. Jason Pardo has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out research and education activities at the Field Museum of Natural History under the mentorship of Dr. Kenneth Angielczyk. Approximately 252 million years ago, a mass extinction event killed 95% of all life on earth, including 80% of all terrestrial species. Exactly what caused this mass extinction is debated, but it is possible that a drop in oxygen levels played a role. One possible line of evidence for this is that the forerunners of mammals evolved a bony shelf that separates their nose from their mouth, allowing them to chew and breathe at the same time. The fellow will test whether this innovation helped the forerunners of mammals survive this mass extinction. Pardo will use medical imaging and computer modeling to test whether separating the nose from the mouth could have made mammals breathe more efficiently, and whether this could explain why some forerunners of mammals went extinct and why others survived. As part of this fellowship, Pardo will produce educational materials through a program at the Field Museum which supports science education in the diverse Chicago Public School system. This research will promote the progress of science by providing insight into the most extreme mass extinction in Earth’s history, as well as how testing how different levels of separation of the nose and mouth (common in some genetic diseases) affect breathing.The End-Permian Mass Extinction (EPME) was a global climatic event which is thought to be responsible for the extinction of 95% of marine species and 80% of terrestrial species, dramatically and permanently reshaping ecosystems in both realms. Although the precise kill mechanism responsible for the terrestrial extinction remains under debate, it is increasingly clear that quantifiable proxies of physiology in Permian and Triassic vertebrates can provide a more precise understanding into how the geological processes responsible for the EPME were translated into patterns of extinction and survival in terrestrial communities, particularly among the forerunners of mammals (therapsids). Pardo will explore the impact of an understudied physiological system, the secondary palate. The secondary palate is a bony separation between the mouth and nasal passages, forming a dedicated upper respiratory system which plays important roles in chewing, suckling, and endothermy, each with direct or indirect ties to respiratory capacity and function. Pardo will explicitly characterize the interplay between the evolution of this system, its physiological relevance, and its effects on therapsid survivorship across the EPME. Pardo will do this in three major aims. Pardo will use CT scanning to precisely quantify variation in the shape of the nasal passage in therapsids with and without a complete secondary palate. Pardo will then use computational and physical models to test whether variation in the shape of the nasal passage and completeness of the secondary palate produce measurable differences in physiological parameters associated with airflow. Finally, Pardo will use phylogenetic comparative methods to test whether these estimable differences in respiratory physiology can predict survivorship across the EPME. Pardo will compare these results with parallel results from scincid lizards, a modern analog of therapsid palate function, in order to confirm biological applicability of Pardo’s results. Pardo’s results will provide a comprehensive framework in which to assess respiratory innovation in the forerunners of mammals as well as the possibility that respiratory stress was a component of the EPME kill mechanism in terrestrial ecosystems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.