''Sorbus arranensis'', sometimes referred to as the Scottish or Arran whitebeam is a species of

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

in the family Rosaceae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the island of Arran in Scotland.

Range and habitat

The species is threatened by

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and only 283 ''Sorbus arranensis'' were recorded as mature trees in 1980. They are protected in Glen Diomhan off Glen Catacol, which was formerly part of a National Nature Reserve; although this designation was removed in 2011 the area continues to form part of a designated Site of Special Scientific Interest (SSSI), and is monitored by staff from

NatureScot NatureScot ( gd, NàdarAlba), which was formerly known as Scottish Natural Heritage, is an executive non-departmental public body of the Scottish Government responsible for the country's natural heritage, especially its natural, genetic and ...

. In its native states its distribution is restricted to Abhainn Bheag (Uisge Solus), Glen Diomhan (and tributary), Glen Catacol, Allt nan Calman, ''Allt Dubh'', Gleann Easan Biorach and Glen Iorsa (''Allt-nan-Champ''). The trees are found in small remnants of woodland on inaccessible steep slopes, and grow on acidic soils. ''Sorbus arranensis'', evoked most collecting interest in 1870–1890 and 1920–1940, although older herbarium specimens exist.

Evolution

The ''Sorbus'' group are apomictic, producing viable seed without the need for pollination and fertilisation. Each time this hybrid cross occurs a new clone is effectively produced. The trees developed in a highly complex fashion, which involved the common whitebeam ('' Sorbus aria'') giving rise to the more robust rock whitebeam (''

Sorbus rupicola ''Sorbus rupicola'', known as rock whitebeam, is a rare shrub or small tree best known from the British Isles but also reported from Norway, Sweden and Russia. Reaching heights of 10 m,''New Flora of the British Isles''; Clive Stace; Third edi ...

'') which is still found on Holy Isle. This hybrid species interbred with the rowan/mountain ash ('' Sorbus aucuparia'') to produce ''S. arranesis''. The bastard mountain ash ('' Sorbus pseudofennica'') arose from a further cross between ''S. arranensis'' and the mountain ash (''S. aucuparia''). Smart showed by using physical characteristics that the species were separate and not a result of random variation. Some overlap does however occur and this suggests that some hybridising may occur between the two species.

References

{{Taxonbar, from=Q1948627 Flora of the United Kingdom arranensis Vulnerable plants Endemic flora of Scotland Endemic biota of the Scottish islands Isle of Arran Taxonomy articles created by Polbot

Range and habitat

Evolution

See also

References