Arran whitebeams complex fashion, which involved the common whitebeam ("Sorbus aria") giving rise to the tetraploid rock whitebeam ("Sorbus rupicola") which is still found on Holy Isle. This species is able to survive at higher altitudes and therefore occupies a less competitive niche with fewer tree species able to tolerate the harsher conditions. The rock whitebeam interbred with the rowan / mountain ash ("Sorbus aucuparia") to produce the hybrid, a fertile separate species the Scottish whitebeam ("Sorbus arranesis") which grows well in this zone of reduced competitive growth at higher altitudes. The bastard mountain ash ("Sorbus pseudofennica") arose from a further cross
Venusia cambrica The larvae feed on the leaves of "Sorbus aucuparia". Other recorded foodplants include alder, apple, birch, mountain ash, serviceberry and willow. Venusia cambrica Venusia cambrica, the Welsh wave, is a moth of the family Geometridae. It is found in Europe, western and central Siberia, Altai, Transbaikalia, the Russian Far East, the Korean Peninsula, Japan and in North America, where it can be found across Canada from Newfoundland and Labrador to British Columbia, south in the west to California, south in the east to Georgia. The wingspan is 27–30 mm. The light grey front wing has black and brown cross lines.