Sorbus rupicola

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Sorbus rupicola
Sorbus rupicola.JPG
Rock whitebeam at the Trondheimsfjord, Norway
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Rosaceae
Subfamily: Maloideae
Genus: Sorbus
Species: S. rupicola
Binomial name
Sorbus rupicola
(Syme) Hedl.

Sorbus rupicola, known as rock whitebeam,[1] is a rare shrub or small tree best known from the British Isles but also reported from Norway, Sweden and Russia.[2]

It can reach heights of 10 m.[3] It grows in rocky woodland, scrub and cliffs, usually on limestone.[3]

The species reproduces apomictically and was presumably created by autopolyploidysation of the common whitebeam proper (Sorbus aria s.str.). It contains a tetraploidal set of chromosomes (2n=4x=68).

A young specimen in Perthshire Scotland
Back of a leaf of a young specimen in Perthshire Scotland
Upper surface of a leaf of a young specimen in Perthshire Scotland
Upper surface of a leaf of a young specimen in Perthshire Scotland
Twig and part of a leaf of a young specimen in Perthshire Scotland

Sorbus rupicola is a member of Sorbus aria agg., which contains 20 subspecies. A key to this aggregate is given in Stace - though be warned Stace states "It is probably impossible to construct a reliable key to the agg."![3] Stace gives Sorbus rupicola the following characteristics:

  • Leaves unlobed or lobed ≤1/20 of the way to the midrib.
  • Leaves with a single style of teeth or, weakly, two styles of teeth.
  • Leaves with 6 to 9 (rarely 4 to 10) pairs of lateral veins.
  • Leaves mostly 1.6 to 2.4 times longer than wide.
  • Leaves mostly widest in that half of the leaf furthest from the stalk.
  • Leaves usually obtuse (rarely acute) at apex.
  • Leaves have dense white hairs on lower surface.
  • Fruits 10-15mm across, warty.

References[edit]

  1. ^ "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-02-25. Retrieved 2014-10-17. 
  2. ^ "Ecological flora of the British Isles: Sorbus rupicola". Retrieved 2010-07-17. 
  3. ^ a b c New Flora of the British Isles; Clive Stace; Third edition; 2011 printing

Further reading[edit]

External links[edit]