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
Sorbus aucuparia Pliocene age. Fruit of "S. aucuparia" were used in the past to lure and catch birds. To humans, the fruit are bitter, astringent, laxative, diuretic, cholagogue, prevent scurvy, and the parasorbic acid irritates the gastric mucosa. Pharmacist Mannfried Pahlow wrote that he doubted the toxicity of the fruit but advised against consuming large amounts. The fruit contain sorbitol, which can be used as a sugar substitute by diabetics, but its production is no longer relevant. "Sorbus aucuparia" fruits have been used in the traditional Austrian medicine internally (as tea, syrup, jelly or liqueur) for treatment of disorders of the respiratory