Long-term dynamics and theoretical considerations in coral holobiont adaptation

Corals are predicted to adapt to environmental change in two ways: through the nuclear evolution of the host and/or through acquiring new, more suitable symbiotic partners. Given the rapid rate of climate change, considerable attention has focused on the latter, as new symbiotic partnerships could, in theory, be formed within one coral generation. Underlying this idea are the assumptions that coral-holobiont partnerships are flexible in response to the environment, and that their flexibility benefits the host. However, the contributions of host genetics, local environment, and time in structuring the holobiont have not been estimated in tandem. This work directly addresses these factors across extended temporal scales through: (1) establishing the feasibility of ancient (6,000-year-old) DNA in coral reef research, (2) determining what structures the holobiont in centuries-old massive corals, and (3) providing a novel theoretical framework for why holobiont shifts occur. From this research, it is clear that host genetics play a strong role in structuring the coral holobiont, suggesting host evolution is essential for reef persistence in future conditions. However, despite many holobiont members remaining present over thousands of years, the local environment and age class have a significant role in structuring the bacterial portion of the coral holobiont. Finally, theoretical modeling of coral bleaching suggests that observed shifts in coral-holobiont partnerships may arise not from adaptation to increasing thermal stress, but rather underlying changes in host demography. Together, these results demonstrate that the evolutionary potential of the coral host cannot be overlooked, as holobiont reassembly alone will likely not create more robust reefs.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Ecology, Evolution and Behavior

Grantor

The University of Texas at Austin

Year dc:date.issued

2024

Author dc:creator

• Scott, Carly Brielle

Advisor dc:contributor.advisor

• Matz, Mikhail V.

Committee members dc:contributor.committeemember

• Ostling, Annette
• Narasimhan, Vagheesh M.
• Lauren Toth

• Evolution
• Eecology
• Cryptic species
• Population dynamics
• Symbiosis
• Mathematical modeling
• Marine biology
• Coral

Identifier URI

https://doi.org/10.26153/tsw/52718

OAI identifier oai:identifier

oai:repositories.lib.utexas.edu:2152/126181