Tuesday , 17 September 2019

Sex changing tree confuses scientists

Fortingall Church, Perthshire. The yew can be seen to the left of the picture.
Fortingall Church, Perthshire. The yew can be seen to the left of the picture.
The oldest tree in Britain appears to have changed its sex, confusing prominent scientists.
 
The Fortingall Yew, which is based in a Perthshire churchyard, is estimated to be between 3,000 and 5,000 years old and has long believed to be male.
 
Male yew trees release pollen while female trees produce bright red berries.
 
However, last month the famous tree – which is reputed to be the birthplace of Pontius Pilate according to local legend – was found to be producing berries. Dr Max Coleman, science communicator at the Royal Botanic Garden Edinburgh, discovered three red berries when examining the ancient tree in 12th October. 
 
Dr Coleman wrote in his blog: “It’s a rare occurrence…rare and unusual and not fully understood. It’s thought that there’s a shift in the balance of hormone-like compounds that will cause this sex-change. One of the things that might be triggering it is environmental stress.”
 
All Yew Need to Know: the difference between a female and male yew tree
All Yew Need to Know: the difference between a female and male yew tree

He continued: “Yews are normally either male or female and in autumn and winter sexing yews is generally easy. Males have small spherical structures that release clouds of pollen when they mature. Females hold bright red berries from autumn into winter. 

 
“It was, therefore, quite a surprise to me to find a group of three ripe red berries on the Fortingall Yew this October when the rest of the tree was clearly male. It seems that one small branch in the outer part of the crown has switched and now behaves as female.”
 
He also confirmed that seeds had been collected from the Fortingall Yew and will now be included in a new scheme to “conserve the genetic diversity” of yew trees by planting them within the botanic garden in Edinburgh. The project aims to replace the current perimeter hedge at the garden with a “hedge” of approximately 2,000 yew trees, grown from cuttings and seeds of various yew trees from across Scotland.
 
Dr Coleman explained: “On completion the hedge will encircle the Garden with a remarkable genetic resource of over 2,000 individual trees, each of which will have a story and can be traced back to their origins in Britain or beyond. This hedge could well be the largest conservation hedge of its kind anywhere in the world.
 
“As it matures the hedge will display a range of characteristics reflecting the genetic diversity of the many individual trees involved and as such it will not look like any existing yew hedge. The Fortingall Yew itself will be represented in the hedge and so too, all being well, will its offspring via the curious ability of yew trees to change sex.” 
 
The phenomenon of the sex-changing tree has generated a great deal of media interest: The Guardian has reported on “how Britain’s oldest tree became ‘sexually ambiguous’”, The Metro led with “Britain’s oldest tree comes out as trans”, while science and technology blog Gizmodo suggested that the tree is “sick of being male”.
 
The ability to change sex is not unusual in some types of trees – trees have been known to change their sex and some, such as the avocado, are understood to do so very quickly. What is baffling about the Fortingall Yew is why a tree so old should opt to undergo the change, and why one branch of it should behave in a different way to the rest of the tree. 
 
Stuart Ryan, from Renfrewshire, a nature enthusiast and landscape photographer who describes himself as “very interested in trees and what lives on them”, told KaleidoScot: “This is absolutely fascinating. I’ve seen this tree and it’s one of the oldest living things in the world. It’s just wonderful that the world is now appreciating this incredible tree we have here in Scotland
 
“The sex lives of trees can be quite remarkable, plants actually procreate but in very different ways.   Birch trees, for example, all have unisexual flowers while alder trees have both male and female flowers on the same tree, which I suppose makes them intersexual. And then we have yew trees, which usually have either male or female reproductive formations.” 
 
Mr Ryan joked: “I’ve been to Fortingall and I had no idea the tree would decide to branch out and do a yew-turn”, before adding “but seriously this is exciting news. For people like me, it gives us an opportunity to learn something new about the life of trees. But I think it also demonstrates that sexuality is complicated – even in trees. It can and often does change. Nature is not as binary as some like to think.”

About Andrew Page

Andrew Page
Andrew is KaleidoScot's sports editor and photographer. An experienced blogger, Andrew was raised in the Hebrides and currently lives in Renfrewshire. Andrew became an active equality campaigner at the time of the Section 28 debate, and has particular interests in faith issues and promoting LGBTI equality in sport. Andrew was shortlisted for the Icon Award's 2015 Journalist of the Year.

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