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
Mountain Ash Comprehensive School Mountain Ash Comprehensive School Mountain Ash Comprehensive School (), known as MACS, is a comprehensive school near Cwmpennar near the town of Mountain Ash, Rhondda Cynon Taf, Wales. The school was formerly known as Mountain Ash Grammar School () and is located near the former Dyffryn Colliery. The Welsh Assembly Government placed all secondary schools in Wales into one of five bands according to a number of factors, such as performance across the three core subjects, attendance levels and the number of pupils on free school meals, with one being the best and five being the worst. Mountain Ash Comprehensive