Welsh groundsel is an allopolyploid, a plant that contains sets of chromosomes originating from two different species. Its ancestor was Senecio × baxteri, an infertile hybrid that can arise spontaneously when the closely related groundsel and Oxford ragwort grow alongside each other. Sometime in the early 20th century, an accidental doubling of the number of chromosomes in an S. × baxteri plant led to the formation of a new fertile species, Welsh groundsel.
Distribution and habitat
It was first discovered in 1948 by Horace E. Green at Ffrith in Flintshire, north-east Wales. The species was described in 1955 by Effie M. Rosser of Manchester Museum using material from the site. It was later found at a number of sites across the north-east of Wales including Chirk, Brymbo, Queensferry and Colwyn Bay and a herbarium specimen was discovered that had been collected at Brynteg in 1925. In England it was reported from Shropshire and an introduced population appeared in Wolverhampton. The Shropshire record is now thought to be erroneous and the Wolverhampton plants have disappeared. There are no recent records from England. In 1982, Welsh groundsel was discovered at several sites around Edinburgh, Scotland. Another case of dual evolutionary locations is Erythranthe peregrina, which arose in two separate parts of Scotland. This population arose independently from the Welsh population; it is believed to date from at least 1974 but now appears to have disappeared with no records since 1993. Typical habitats of the species include waste ground, roadsides and cracks in walls and pavements.
Description
The plant is intermediate in appearance between its parents, groundsel and Oxford ragwort. It is an erect annual plant that reaches a height of 30 centimetres. The stem and leaves have few or no hairs. The leaves are deeply lobed. The lower leaves have stalks, whereas the upper leaves are attached directly to the stem. The flower heads are cylindrical and usually have 8 to 15 yellow ray florets although some are rayless. The ray florets vary in length but are most commonly 4 to 7 mm long. The pollen grains are 30 to 36 micrometres across and usually have 4 pores.
