Scientists and reef managers are now calling for \u201cassisted evolution\u201d to help accelerate adaptation<\/a>. One promising approach is selective breeding to enhance heatwave tolerance. <\/p>\n Our new study<\/a> explores how such interventions could help corals<\/a> withstand future heatwaves.<\/p>\n By examining the genetic basis of heat tolerance and other important life history traits including growth, energy reserves and reproduction, we reveal both the potential, and limits, of evolutionary adaptation to extreme heat stress. This work focuses on a captive-bred coral population we reared over eight years in Palau, an archipelago in the west Pacific.<\/p>\n Mass coral bleaching during an intense marine heatwave. The field of quantitative genetics can shed light on complex traits such as growth and heat tolerance, which are typically influenced by hundreds to thousands of genes. These tools can help us maximise evolutionary responses to selection, and have long been used in agriculture and animal breeding \u2013 from the crops we eat to the dogs we have at home.<\/p>\n Two key concepts are central. \u201cGenetic merit\u201d describes the value of an individual for breeding, and \u201cgenetic correlations\u201d describe how traits share their underlying genetic basis.<\/p>\n Estimating these requires measuring certain traits like heat tolerance, and collecting information about relatedness among individuals, such as full- or half-siblings. But this is difficult in wild corals, which disperse widely and are typically unrelated to neighbouring individuals on the reef.<\/p>\n Our captive population, containing both related and unrelated individuals, provides a rare opportunity to apply quantitative genetics to adult corals.<\/p>\n Read more: Imagine a major heatwave has caused widespread coral mortality. Which corals should we select for propagation or breeding?<\/p>\n Choosing survivors seems intuitive, but survival alone does not guarantee a genetic predisposition for heat tolerance. A coral could survive by chance \u2013 perhaps it was shaded or had higher energy reserves, while all its relatives died. Selecting such individuals for breeding would fail to improve heatwave tolerance of future generations.<\/p>\n However, if entire families tend to survive or perish together, that indicates a genetic basis for heatwave tolerance. Using quantitative genetics in such cases can help make more informed choices.<\/p>\n But if no natural heatwave occurs, how can we proactively identify good corals for management? To do this, we need a proxy: an easy-to-measure trait that is genetically correlated with \u2014 and so predicts \u2014 an individual\u2019s genetic merit for heatwave survival.<\/p>\n We tested coral heat tolerance under four different temperature exposures, ranging from a month-long exposure of 32.5\u00b0C to a rapid heatshock reaching 38.5\u00b0C. <\/p>\n These high experimental temperatures go beyond what happens in nature. As the simulated conditions grew hotter, we found ever weaker genetic correlations with marine heatwave survival. These tolerance traits exhibit somewhat distinct underlying biology, so careful trait choice is essential. Testing the wrong proxy traits to identify target corals will fail to deliver any heatwave survival enhancement.<\/p>\n Liam Lachs and Adriana Humanes in the coral lab. But adaptation involves more than just heat tolerance. Individual growth, energy reserves and reproduction are all critical for healthy populations. If enhancing heat tolerance comes at the cost of traits like these, it would undermine population viability.<\/p>\n Encouragingly, we found no detectable negative genetic correlations among any of the traits we studied.<\/p>\n Matching future stress<\/p>\n To explore how assisted evolution could enhance heat tolerance over time, we developed a computer simulation. <\/p>\n This showed us it was possible to reach tolerance levels capable of withstanding future heatwaves, but only under certain conditions.<\/p>\n Selection needed to directly target long-term heatwave survival. This meant choosing only the top 5% most tolerant corals as parents for breeding, and it had to be repeated over multiple generations. <\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/file-20260416-77-krmaad.jpg\")
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\n Liam Lachs<\/p>\n
\n We\u2019ve bred corals to better tolerate lethal heatwaves, but rapid climate action is still needed to save reefs<\/a><\/p>\n![\"two](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/file-20260416-63-jihtu1.jpeg\")
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\n Tries Razak, CC BY-NC-ND<\/a><\/p>\n
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