McGill University
Ph.D. candidate
Supervisor: Rowan Barrett
Sean Connolly, Smithsonian Tropical Research Institute (STRI)
Start: 2019-09-03
End: 2024-12-02
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Project

Host-microbiome dynamics impact the thermotolerance of cnidarian holobionts
Understanding the mechanisms underlying organismal responses to environmental stress has been a long-standing pursuit in evolutionary biology, but anthropogenic climate change has turned this interest into an imperative. There is growing appreciation for the importance of interactions between a host and its microorganisms (“microbiome”) for species resilience to environmental change. The holobiont theory emerged in response to this rapidly evolving field, arguing that a host and its microbiome are a single unit under selection, reciprocally impacting each other’s development, fitness, and evolution. In this dissertation, I explore these interactions through a holobiont lens using the reef-building Pocillopora coral and the sea anemone Aiptasia as model organisms. In Chapter 1, I explore how environmental and geographic factors are structuring Pocillopora corals’ Symbiodiniaceae algal symbioses across the Indo-Pacific. In analyzing publicly available data for these symbioses, sea surface temperature emerged as the primary driver of algal community differences, with geographical isolation explaining these patterns to a lesser extent. My meta-analysis is one of the few studies to explicitly explore coral holobionts from a biogeographical perspective, further supporting the hypothesis that algal symbionts may be implicated in coral host thermotolerance. In Chapter 2, I focus on Pocillopora coral reefs in Panama’s Tropical Eastern Pacific (TEP) to assess how seasonal upwelling influences host-microbiome configurations and holobionts’ resistance to increasing water temperatures. To do so, I studied colonies in-situ and subjected them to a thermal assay known as the Coral Bleaching Automated Stress System (CBASS). Contrary to expectations, I found little host genetic differentiation across upwelling regimes, yet there were signatures of divergent selection on genes with functions previously implicated in bleaching. During the CBASS, genetic lineage, region, and temperature collectively mediated algal symbiont shifts in response to thermal stress. This pattern with algal symbionts strongly contrasted with temperature-driven dysbiosis for the prokaryotic community. Additionally, corals under seasonal upwelling experienced more stressful baseline conditions, which may contribute to their higher predicted thermal thresholds. My holobiont approach reveals how corals’ adaptation and acclimation mechanisms are potentially impacted by upwelling, providing new insights into how host and microbiome responses synergistically impact resilience to climate change. In Chapter 3, I build upon my findings in Chapter 2 using the sea anemone Aiptasia as a model for corals. I investigated how algal symbiont’s thermal sensitivity impacted prokaryotic dynamics by subjecting clonal Aiptasia lines hosting either a thermotolerant or thermally sensitive algae to a heat stress assay that triggers bleaching. I found that algal strain was the strongest driver of the Aiptasia prokaryotic microbiome, presenting prokaryotic taxa that may be potential indicators of both improved and reduced bleaching resilience. Additionally, I propose that sustained community variance, as opposed to increased variance as a function of temperature, may be characteristic of more thermally sensitive cnidarian holobionts. My work is the first to explicitly control for Aiptasia host genetic lineage in characterizing prokaryotic community dynamics under heat stress, underscoring how algal and prokaryotic dynamics together may result in different bleaching trajectories. Collectively, my thesis presents that the host and its microbiome are not only a single unit under selection, but also one collectively responding to climate change. In studying corals and sea anemones, my work’s holobiont approach emphasizes that considering how microorganisms influence the ecology and evolution of organisms can reveal novel perspectives into the factors that contribute to climate resilience.

Keywords

metagenomics, genomics, adaptation, Coral reefs, Microbiome, thermotolerance, climate change

Publications

1- Interactive effects of multiscale diversification practices on farmland bird stress
Olimpi, Elissa M., Hallie Daly, Karina Garcia, Victoria M. Glynn, David J. Gonthier, Claire Kremen, Leithen K. M'Gonigle, Daniel S. Karp
2022 Conservation Biology

2- Environmental and geographical factors structure cauliflower coral's algal symbioses across the Indo‐Pacific
Glynn, Victoria M., Steven V. Vollmer, David I. Kline, Rowan D. H. Barrett
2023 Journal of Biogeography

3- Engineering Kluyveromyces marxianus as a Robust Synthetic Biology Platform Host
Cernak, Paul, Raissa Estrela, Snigdha Poddar, Jeffrey M. Skerker, Ya-Fang Cheng, Annika K. Carlson, Berling Chen, Victoria M. Glynn, Monique Furlan, Owen W. Ryan, Marie K. Donnelly, Adam P. Arkin, John W. Taylor, Jamie H. D. Cate,
2018 mBio

4- Harnessing open science practices to teach ecology and evolutionary biology using interactive tutorials
Griffith, Jory E., Elizabeth Houghton, Margaret A. Slein, Maxime Fraser Franco, Jhoan Chávez, Amy B. Forsythe, Victoria M. Glynn, Egor Katkov, Kirsten M. Palmier, Zihaohan Sang, Rolando Trejo‐Pérez, Bryn Wiley, Jennifer M. Sunday, Joey R. Bernhardt
2024 Ecology and Evolution