Saturday, 27 April 2013

Recent Evolution in Britain

Senecio cambrensis
A lovely example of the very recent evolution of an entirely new plant species has been discovered in North Wales. I'm grateful to @Kaimitai on Twitter for bringing it to my attention.

The new species, Senecio cambrensis, also known as Welsh groundsel or Welsh ragwort, arose as a fertile allopolyploid hybrid between S. vulgaris or common groundsel, and S. squalidus or Oxford ragwort. Hybrids of these two species are the fairly common but sterile S. x baxteri (in taxonomic nomenclature 'x' indicates a hybrid) which is thought to have been the actual ancestor of S. cambrensis. Sometime in the early 20th century an accidental doubling of the chromosome number led to a fertile plant - the Welsh groundsel.

Left: Senecio vulgaris. Right: Senecio squalidus.
The new species can only reproduce with other members of its own species making it indisputably a new species - contrary to the claim made by Creationist pseudo-scientists that evolution cannot give rise to new species.

It was discovered in 1948 by Horace E. Green growing at Ffrith, Flintshire, Wales and was first systematically described in 1955 by Effie M. Rosser of Manchester Museum. In 1982 S. cambrensis was discovered growing in several sites near Edinburgh, Scotland. This population is believed to have arisen independently of the North Walian population in about 1974 but had disappeared by 1993. It has been reported, probably mistakenly, in Shropshire, England and more reliably at Wolverhampton, England. The Wolverhampton population now also seems to have disappeared.

One of the original parent species, S. squalidus or Oxford ragwort is an alien species in Britain having been introduced from Sicily in the 18th century. It's own history in the UK is an interesting example of how environmental change can bring about evolutionary change:
This Senecio [S. squalidus] was introduced into Britain via Francisco Cupani and William Sherard in the years of their visit 1700, 1701 and 1702 from Sicily where it lives as a native on volcanic ash to the Duchess of Beaufort's garden at Badminton. Later a transfer of the genetic material to the Oxford Botanic Garden by the "Horti Praefectus" (the title still given to the head gardener at the Oxford Botanic Garden) Jacob Bobart the Younger before his death in 1719 (which is also the same year that Bobart retired as Horti Praefectus and perhaps a good indication of when this species of ragwort and other invasive species might have "escaped" and started to make their home in the greater British Isles). The Sicilian ragwort escaped into the wild and grew in the stonework of Oxford colleges (with the specific mention of the Bodleian Library) and many of the stone walls around the city of Oxford. This gave the plant its common name, "Oxford Ragwort".

The vortex of air following the express train carries the fruits in its wake. I have seen them enter a railway-carriage window near Oxford and remain suspended in the air in the compartment until they found an exit at Tilehurst [near Reading, Berkshire, some 20 miles south-east of Oxford].

George Druce, 1927
Carolus Linnaeus first described Senecio squalidus in 1753, although there is a dispute as to whether the material came from the Botanic Garden or from walls in the city; the taxonomy for this species is further complicated by the existence of species with a similar morphology in continental Europe.

James Edward Smith officially identified the escaped Oxford ragwort with its formal name Senecio squalidus in 1800.

During the Industrial Revolution, Oxford became connected to the railway system and the plant gained a new habitat in the railway lines clinker beds, gradually spreading via the railway to other parts of the country. The process was accelerated by the movement of the trains and the limestone ballast that provides a well-drained medium which is an adequate replica of the lava-soils of its native home in Sicily.
So, from an escaped botanical specimen in Oxford, Oxford ragwort has spread throughout the UK assisted by human agency and facilitated by the Industrial Revolution - a process which is continuing today with other species with wind-distributed seeds by being blown along motorways and highways in the direction of traffic. It is now a widespread and common species and is something of a pest in the New Forest where regular eradication campaigns are conducted because it is thought to be harmful to the horses which roam freely in the forest.[However, see Update below]

There we have not only another example of recent speciation by hybridization, so disconcerting to Creationists, but a nice example of how environmental change can facilitate and drive evolution. Who would be a Creationist pseudo-scientist having to hope his credulous target market remains ignorant of this sort of information, especially when they have the Internet to contend with? What a way to earn a living!

No wonder religious superstition is declining so rapidly these days and is becoming more and more the province of the ignorant and scientifically illiterate upon whom Creationist cheats and con artists prey.

[Update 3 may 2013]
I am indebted to fellow blogger mabymynydd who has pointed out that it is the native Common Ragwort (Senecio jacobaea), not the Oxford Ragwort (S. squalidus) which is considered by some to be a pest in the New Forest, though the danger to horses is disputed. See comment below.





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3 comments :

  1. checkmate creationists a living explanation/evidence is here for transfer of species from water to surface how fins developed to accommodate locomotion on surface 9 new species with hands evolution at work- nat geo also another one Image on facebook about the new found fishes in australia

    ReplyDelete
  2. I applaud your blog generally, anything to knock the creationist nonsense should be encouraged however you are confused about the ragwort control in the New Forest. This is not about Oxford Ragwort but Common Ragwort which is a NATIVE plant.
    Common Ragwort is an ecologically valuable plant that is very occasionally poisonous, but that has been subjected to a hysterical and unscientific campaign of destruction. In the main area where S. cambrensis grows I fear the local ragwort campaign may lead to its extinction.

    Anti-ragwort campaign is very much like creationism. I blog on this and there is a perfect example from the S. cambrensis area here http://ragwort-hysteria.blogspot.co.uk/2012/04/british-horse-society-spokespersons.html

    It is evolution that shows that the living plant which is distasteful is not eaten by animals. Those that ate it in the past did not pass on their genes.

    In the latest entries on the blog I document exactly the same kind of insistence on ignorant belief that I have encountered in debating creationists.

    ReplyDelete
    Replies
    1. Thank you. I stand corrected on that point.

      Delete

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