Date of Award

5-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean Engineering and Marine Sciences

First Advisor

Robert van Woesik

Second Advisor

Toby S. Daly-Engel

Third Advisor

Kelli Z. Hunsucker

Fourth Advisor

Richard B. Aronson

Abstract

Marine heatwaves are increasing in intensity and frequency because of increased emissions of greenhouse gases. On coral reefs, warmer temperatures cause coral bleaching, mortality, and shifts in benthic composition. However, coral bleaching responses and survival vary geographically. Several hypotheses may explain such geographical differences in thermal tolerance, including the possibility that some localities may support higher intraspecific diversity than other localities, increasing the likelihood of survival of some individuals through heatwaves. Here we assessed geographic patterns of intraspecific genetic diversity in the ubiquitous coral Pocillopora damicornis. Intraspecific genetic diversity was assessed for 428 sequences across 44 sites in the Pacific and Indian Oceans. We found the highest intraspecific genetic diversity within sites in Southeast Asia in the western Pacific Ocean, north of the Equator, with a decreasing gradient from west to east across the Pacific Ocean. Southeast Asia was also a divergence point, supporting 21% of the unique haplotypes, suggesting a potential site of species origin. Sites in Southeast Asia that have high genetic diversity are more likely to support individuals who harbor alleles that may prove adaptive potential and thereby survive environmental disturbances, such as marine heatwaves. The reefs in Southeast Asia, in the Coral Triangle region, should be given high conservation priority as these corals have the highest adaptive potential to climate change.

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