Latest news with #ashTrees
Times
20 hours ago
- Health
- Times
Ash trees evolving resistance to dieback
The forces of evolution are helping Britain's ash trees to fight back against a deadly fungus that has threatened to decimate the species, a study suggests. After ash dieback was first recorded in the UK in 2012 experts warned that the disease had the potential to 'change the landscape for ever' by killing up to 90 per cent of Britain's 150 million ash trees, which in 2019 accounted for about 12 per cent of the nation's broadleaf woodland. However, analysis suggests that natural selection — the evolutionary process first described by Charles Darwin — is already favouring traits that will help young ash survive. Ash trees were felled in places such as Lower Woods, Gloucestershire, to limit the spread of dieback ALAMY Scientists from the Royal Botanic Gardens, Kew, and Queen Mary University of London compared older trees with new saplings. They found thousands of genetic differences that appeared to be allowing younger trees to withstand the fungus more successfully than their predecessors. Professor Richard Buggs, a senior scientist at Kew and co-author of the study, said the research had raised hopes that ash could fare better than Britain's elms, which were all but wiped out by Dutch elm disease. 'These findings suggest that ash will not go the way of the elm in Britain,' Buggs said. 'Elm trees have struggled to evolve to Dutch elm disease [because of low levels of genetic diversity] but ash are showing a very different dynamic because they produce an abundance of [genetically different] seedlings upon which natural selection can act when they are still young.' Ash dieback causes leaf loss and stem lesions and often results in trees dying. The research team analysed trees in Marden Park wood in Surrey, a site managed by the Woodland Trust. By studying thousands of variants of different genes, they identified subtle changes between generations. Charles Darwin's theory of evolution proposes individuals within a species most suited to their environment will survive and pass on those benefits to their offspring ALAMY 'A tragedy for the trees has been a revelation for scientists, allowing us to show that thousands of genes are contributing to the ash trees' fightback against the fungus,' said Professor Richard Nichols, an evolutionary geneticist at Queen Mary University London. Even so, the researchers warned that the future of the species in Britain was not guaranteed. 'Natural selection alone may not be enough to produce fully resistant trees. The existing genetic variation in the ash population may be too low and, as the trees become scarcer, the rate of selection could slow,' said Dr Carey Metheringham, an author of the study, which has been published in the journal Science. 'Human intervention, such as selective breeding and the protection of young trees from deer grazing, may be required to accelerate evolutionary change,' Metherington added.
The Guardian
20 hours ago
- Science
- The Guardian
‘New hope': ash trees rapidly evolving resistance to dieback, study reveals
New generations of wild ash trees are rapidly evolving resistance to the fungus devastating their numbers, scientists have discovered. The discovery gives hope, the researchers said, and shows that allowing the natural regeneration of woodlands is vital to enabling this evolution to take place. However, it remains too early to say if the development of resistance in the ash trees can outpace the destruction being caused by the ash dieback fungus. The genetic analysis is also a scientific breakthrough. It is the first convincing proof of a prediction made by Charles Darwin that significant changes in organisms can result from natural selection driving very many small changes, not just from one or two obvious ones. Ash dieback is caused by the invasive Hymenoscyphus fraxineus fungus, which was first identified in the UK in 2012 and is also killing trees across Europe. It has killed millions in the UK and is expected to wipe out up to 85% of the older, non-resistant ash trees, incurring costs of £15bn. Previous studies found apparent resistance in some ash saplings but the new study gives in-depth genetic information that could help breeding programmes to support the natural recovery of ash trees. 'Our new findings give us new hope,' said Prof Richard Buggs, at the Royal Botanic Gardens Kew and Queen Mary University of London (QMUL): 'Elm trees have struggled to evolve to Dutch elm disease, but ash produce an abundance of seedlings upon which natural selection can act when they are still young. Through the death of millions of ash trees, a more resistant population of ash is appearing.' Prof Richard Nichols, also at QMUL, said: 'We have to be cautious. We can't say the ash is saved, but we are in a position to say it's looking promising. We are watching evolution happen and what's remarkable is that it's happening so quickly, in a single generation.' One ash tree can produce 10,000 genetically distinct seeds in one season, leading to scores of saplings. The study, published in the journal Science, compared the DNA of trees that were already growing before ash dieback's arrival with younger trees that were established after. The new trees have to grow up through the leaf mould where the fungus replicates and the researchers found that about 30% of these were killed by ash dieback, providing a strong driving force for evolution. 'Only the fittest survive – those that made it through that intense early episode of selection,' said Nichols. Previous genetic work had identified thousands of locations in ash DNA that appeared to either protect the trees from dieback, or make them more vulnerable. The scientists recorded subtle changes at these locations, showing the younger generation possessed greater resistance than their predecessors. This showed that the DNA changes predicted whether saplings were more likely to flourish or die and therefore demonstrated that Darwinian evolution by natural selection was taking place. Sign up to Down to Earth The planet's most important stories. Get all the week's environment news - the good, the bad and the essential after newsletter promotion Ash dieback kills trees slowly and Nichols said the research showed the best strategy was to keep as many trees alive as possible to allow their offspring to evolve. Felling and destroying infected trees would mean important genetic variability was lost. Rebecca Gosling, of the Woodland Trust, which owns Marden Park woods in Surrey, where the study took place, said: 'The findings highlight how vital it is to support natural regeneration in woodlands, furthering our understanding of how to best manage our ash woodlands.' 'However, natural selection alone may not be enough to produce fully resistant trees,' said Dr Carey Metheringham, at QMUL. 'The existing genetic variation in the ash population may be too low, and as the trees become scarcer, the rate of selection could slow.' Therefore, human interventions may also be required to support ash tree recovery, the researchers said. This could include selective breeding for resistant varieties, cross-breeding with Asian ash trees, which evolved with the fungus and are therefore highly resistant, or even gene editing.
