One-year-old, pedigree-tracked corals growing in an ocean nursery.
Photo Credit: Dr Liam Lachs
Scientific Frontline: Extended "At a Glance" Summary: Assisted Coral Evolution and Trait Selection"
The Core Concept: Assisted evolution is a proactive conservation strategy designed to accelerate the natural adaptation rates of corals, enabling them to survive increasingly severe marine heatwaves. It relies on the selective breeding of corals based on specific heritable traits, including growth, reproduction, and thermal tolerance.
Key Distinction/Mechanism: Unlike natural adaptation, which is unlikely to keep pace with rapid oceanic warming, assisted evolution requires intense, repeated intervention. This methodology isolates the top 1-5% most heat-tolerant corals for use as broodstock over multiple generations, specifically targeting the genetic merit of the coral host rather than its symbionts.
Major Frameworks/Components:
- Pedigree-Tracked Populations: Utilizing multi-generational, documented coral families to accurately map trait inheritance and observe offspring performance.
- Advanced Statistical Modeling: Estimating the genetic merit for heat tolerance and ensuring no negative genetic correlations exist between thermal resilience and other vital fitness traits (e.g., calcification, tissue biomass).
- Sustained High-Intensity Selection: Implementing aggressive selection pressures (identifying the top 1-5% as broodstock) across successive generations to yield meaningful evolutionary gains.
- Host-Targeted Intervention: Focusing genetic improvements directly on the coral organism rather than altering its symbiotic microalgae.
Branch of Science: Evolutionary Biology, Marine Ecology, Conservation Genetics, Marine Biology.
Future Application: This research establishes a blueprint for large-scale, strategic coral reef conservation. Selectively bred broodstock can be deployed in ocean nurseries and targeted local environments to bolster reef resilience against climate-driven temperature anomalies.
Why It Matters: Marine heatwaves are driving widespread coral bleaching and mass mortality events globally. While greenhouse gas reduction remains the primary necessity to halt ocean warming, assisted evolution provides a critical, localized mitigation tool to preserve foundational marine species and the vital ecosystems they support.
Assisted evolution could help corals survive future heatwaves, but careful trait choice and strong repeated selection will be needed for it to be effective.
As global temperatures rise, marine heatwaves are becoming more frequent and severe, driving coral bleaching and mortality. While some coral populations are already showing signs of natural adaptation, researchers warn that these changes are unlikely to keep pace with future warming.
A new study published in Current Biology explores whether host assisted evolution, which aims to accelerate natural adaptation rates of corals, could help them survive future heatwaves and what it would take to achieve required tolerance gains.
The international research team, led by Newcastle University, have created a unique, pedigree-tracked coral population over the last eight years, allowing them to map family relationships and measure how multiple key traits—such as growth, reproduction and survival—are inherited.
By combining information on multiple traits for each coral, their family relationships and advanced statistical modelling, the scientists were able to estimate each coral’s genetic merit for heat tolerance and other traits, and the genetic links among traits, insights that go beyond what can be simply observed.
Dr James Guest, Reader in Coral Reef Ecology at Newcastle University and the principal investigator of the project supporting this study, said: “Developing and maintaining this pedigree-tracked coral population has driven a step change in our ability to identify which traits to select for to enhance tolerance under future climate stress. Being able to produce corals from parental colonies with known histories and well-characterized traits—and then observe how this genetic information influences offspring performance—has significantly advanced our understanding of how assisted evolution can be effectively implemented to conserve coral reefs.”
The results show that assisted evolution methods targeting the coral host—rather than its symbionts—will require choosing the right traits and repeatedly selecting corals over multiple generations to strengthen those traits.
Selection must directly target long-term heatwave survival, or traits that have a strong genetically based correlation to heatwave survival. To keep pace with climate change, efforts will need to implement very strong selection, choosing the top 1-5% most tolerant corals as broodstock. And this process will have to be repeated over multiple generations to achieve desired evolutionary benefits. Such intense selection introduces other challenges, including the maintenance of genetic diversity and practicality of scaling up selection efforts.
Study lead author, Dr Liam Lachs, a former Postdoctoral Research Associate at Newcastle University’s School of Natural and Environmental Sciences and current Research Fellow at University of Queensland, Australia, said: “Local adaptation involves more than just heat tolerance. Traits like growth, reproduction, calcification, tissue biomass, and symbiont flexibility all contribute to overall fitness. If improving heat tolerance came at the cost of these traits, it could undermine population viability. But encouragingly, we found no detectable negative genetic correlations among any traits; good news for assisted evolution interventions.”
Not a silver bullet
The researchers stress that assisted evolution is not a substitute for cutting greenhouse gas emissions, which remains essential to limit ocean warming.
However, as global mitigation efforts continue, targeted local interventions could play an important supporting role at certain scales. Strategic conservation approaches, including assisted evolution, may help key coral species adapt and persist in a rapidly changing climate.
Study lead author, Dr Adriana Humanes, a Research Associate at Newcastle University, said: “Our results show that increasing coral heat tolerance can, in principle, deliver meaningful gains for coral persistence. But success will depend on choosing the right traits and strong, sustained selection. While reducing greenhouse gas emissions is still the main priority to mitigate the warming corals face, other mitigation efforts such as assisted evolution will be crucial to help key species adapt and persist in our rapidly warming world.”
Published in journal: Current Biology
Title: Choice of traits defines the scope for assisted evolution of corals under climate change
Authors: Liam Lachs, Adriana Humanes, Cinzia Alessi, Asap Bukurrou, John C. Bythell, Daniel Cassidy, Alasdair J. Edwards, Yimnang Golbuu, Leevan Manuel, Helios M. Martinez, Eveline van der Steeg, John E. Stratford, Ruben de la Torre Cerro, Alastair J. Wilson, and James R. Guest
Source/Credit: Newcastle University
Reference Number: ebio041826_01
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