14. Arran Whitebeam
Sorbus arranensis Hedl.
Native Range: Island of Arran, Scotland.
This rare Scottish tree is endemic to Arran and is restricted in range to the north end of the island where it grows in rocky steep sided glens between 100m to 300 m.
The earliest known description of the Arran Whitebeam is that of Alexander Craig Christie in 1869.
Sorbus arranensis is believed have resulted from the rare crossing of Sorbus aucuparia (Rowan) and Sorbus rupicola (Rock Whitebeam). A unique clonal population (microspecies) then grew from the seeds of the hybrid. This happens through a form of asexual (non-sexual) reproduction (agamospermy).
The species has been at the centre of conservation work along with another species the Arran Service Tree (Sorbus pseudofennica). In 1954 a National Nature Reserve was set up to protect and manage the habitats growing around the trees and in 1984 a trial population reinforcement programme was implemented. Work is still continuing on the species at Royal Botanic Garden Edinburgh as part of the Target 8 Project. The Target 8 Project is one of the targets set out in the Global Strategy for Plant Conservation, which aims to conserve 75% of threatened native species in cultivation. Sorbus arranensis is one of theses threatened species due to habitat loss, severe weather and over grazing by sheep and cattle. There is thought to be only around 500 plants left growing in the north of the Isle of Arran.
Wigginton, M.J. 1998. Sorbus arranensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>.