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 a source for fruit in harsh mountain climate and Maria Theresa of the Habsburg Monarchy recommended the planting of the species in 1779. An edible variety, named "Sorbus aucuparia" var. "dulcis" Kraetzl, or var. "edulis" Dieck, or var. "moravica" Dippel, was first discovered in 1810 near Ostružná in the Hrubý Jeseník mountain range of Northern Moravia and became widespread in Germany and Austria the early 20th century. Its leaves are larger and pointed, only the front part of the leaflets is serrated, and they have darker bark, larger buds and larger fruit. Similar non-bitter varieties found in Southern Russia were