29 April 2013

Yellow Whitlowgrass 2013 survey

Karen Wilkinson (Natural Resources Wales) wrote:
'Early in April Mervyn Howells, myself and a handful of other volunteers undertook a survey of Draba aizoides (Yellow Whitlowgrass) of the south Gower Coast. Gower is the only known UK location for this species in the UK, although it is also found in the mountain ranges across Europe such as the Alps, the Pyrenees, the Carpathians and the Jura mountains. It grows in cushions in crevices and on ledges along the Carboniferous Limestone from Pwll Du in the east to Tear’s Point in the west. As it is an early flowering species, its yellow flowers are particularly distinctive at this time of year before most other species are in flower.
Mervyn has been monitoring the populations for more than 20 years and has an amazing knowledge of the distribution of plants which often occur in very precarious situations! Although it clearly has a limited distribution in the UK, in Gower it does appear to be stable; this year around 1400 plants were recorded. This is likely to be an underestimate as some locations are extremely difficult to survey safely, where we also noticed good numbers of plants growing in the grassland sward at the top and bottom of cliffs. This may be partly due to changes in grazing pressure or might be related to successful seed production or seed germination in recent years.
Distribution map of all pre-2013 records of Yellow Whitlowgrass
(results from 2013 show a very similar pattern)

During the survey we also noticed a larger population of Sedum album (White Stonecrop) than we were previously aware of, primarily along the thin band of therophytic vegetation on the cliff tops. This plant is frequent in the droughted slopes around Port Eynon and we are keen to keep an eye on its spread west and its effects on the local flora. If anyone has any new or historic records for this species we would be interested in hearing from you.'
Distribution map of all pre-2013 records of White Stonecrop
(pre-2000 records shown by smaller dots)


Ian Morgan said...

I seem to recall that, in the c mid-1990s, genetic work was carried out (Quentin Kay et al?)on the Draba, along with other species. This was part of a CCW commission. Is there access to this report?....I`m particularly interested to which of the European populations Draba is most closely related.

Charles Hipkin said...

Ian, the work you are referring to was carried out by Rosemary John. She carried out an isozyme analysis on Gower plants and plants from Belgium and the Alps. The results suggest that the Gower population has been there long enough to discount introduction by people, and in particular the Normans. Its occurrence on the walls of Pennard Castle had suggested (to some) that it may have been brought to Gower in the Middle Ages. The full details are contained in her PhD thesis which is available from Swansea University Library.

Ian Morgan said...

Thanks Charles - appreciated. I`ll get hold of it - Ian