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
× Sorbaronia mitschurinii × Sorbaronia mitschurinii × "Sorbaronia mitschurinii, also known as Sorbaronia mitschurinii", is a domesticated species that was known until recently under the name "Aronia mitschurinii". It has been considered to be a group of cultivars of "Aronia melanocarpa", common ones including 'Viking' and 'Nero'. Genetic testing indicates it is likely a hybrid between "A. melanocarpa" and "Sorbus aucuparia" (mountain ash) that apparently originated in cultivation. It has been suggested that "Sorbaronia mitschurinii" is the product of Russian pomologist Ivan Vladimirovich Michurin's early 20th century experiments in wide hybridizations. This species is more robust than wild populations of "Aronia melanocarpa"; the