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
Burrington Combe as a Site of Special Scientific Interest in 1952. The calcareous grasslands support a diverse flora which includes Salad burnet ("Sanguisorba minor"), Knapweed ("Centaurea scabiosa" and "Centaurea nigra"), Rock-rose ("Helianthemum nummularium") and Wild thyme ("Thymus praecox"). On the higher, more acidic, slopes Goldenrod ("Solidago virgaurea"), Wood sage ("Teucrium scorodonia") and Common Bent ("Agrostis capillaris") can be found. There are also scrub plants including Hawthorn ("Crataegus monogyna"), Mountain ash ("Sorbus aucuparia"), gorse ("Ulex europaeus") and Elder ("Sambucus nigra"). Several of the caves support bat populations. Geologically it is recognised as a fluvial karst feature which partly intersects a buried and filled