Parasitism and mass extinction: How did parasite prevalence, abundance, body size and host growth and longevity respond to the Pliocene-Pleistocene molluscan host turnover?

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Despite their negative reputations, parasites are important parts of healthy ecosystems. They have been shown to promote increased biodiversity in living communities and stabilize the population sizes of other species. Many parasites rely on three or more other species to complete their life cycle and their success reflects a well-functioning ecosystem. What happens to these parasites and hosts after a mass extinction? This research will evaluate the impact of a 2.5-million-year-old mass extinction on flatworm parasites and their clam hosts in the western Atlantic Ocean. Understanding parasite-host responses to this geologically recent extinction can give us insights into how economically valuable living clam populations and their parasites will respond to ongoing biodiversity loss. The Broader Impacts portion of this project will promote science education by supporting a STEM camp for elementary and middle grades students at the University of Missouri. Mass extinctions not only disrupt phylogenetic lineages but can fundamentally alter ecological interactions within the affected ecosystems. Little is known about how extinction events influenced parasite-host interactions in geologic time. A major regional extinction event took place among western Atlantic mollusks during the Plio-Pleistocene transition, and this project will utilize the well-characterized fossil record of bivalve hosts bearing traces induced by their flatworm parasites to test the following hypotheses: 1) parasite prevalence, abundance, and aggregation systematically decreased among host taxa following the extinction; 2) trematode pit size distributions (as a parasite taxonomic proxy) changed significantly following the extinction event; 3) host body size and longevity within a taxon was suppressed by high parasite prevalence and increased when released from parasitism pressure; and 4) geochemical proxies from the fossil bivalves will reveal spatial variation in the importance of multiple environmental drivers. This project will be transformative by revealing how biotic overturn has influenced parasite-host interactions in the geologically recent past and will provide insight into how currently elevated extinction rates may cause such interactions to change in the coming decades to centuries. As such, this work will be of broad interest in paleobiology, geology, ecology, parasitology, and epidemiology. The Broader Impacts plan of this project addresses scientific literacy in the areas of deep time, biological evolution, and environmental change by expanding a science day camp in collaboration with colleagues at Mizzou Paleo and the University of Missouri’s The Connector. Mizzou Rocks! is for rising 4th-6th grade students where students learn to identify minerals, rocks, and fossils common in Missouri; become familiar with the broad strokes of Earth and life history; build quantitative skills while learning about megafauna locomotion; and learn geology in the field. 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.