Sorbus rupicola, known as Rock Whitebeam, is a rare shrub or small tree best known from the British Isles

British Isles

The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

 but also reported from Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 and Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. It prefers basic

Base (chemistry)

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

 soil near edges of forests or other shrubs. If growing to full trees, S. rupicola can reach heights of 3—5 m. The species recreates apomictically

Apomixis

In botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...

 and was presumably created by autopolyploidysation

Polyploidy

Polyploid is a term used to describe cells and organisms containing more than two paired sets of chromosomes. Most eukaryotic species are diploid, meaning they have two sets of chromosomes — one set inherited from each parent. However polyploidy is found in some organisms and is especially common...

 of the common Whitebeam proper (Sorbus aria

Sorbus aria

Sorbus aria , the Whitebeam or Common Whitebeam is a deciduous tree, compact and domed, with few upswept branches; it generally favours dry limestone and chalk soils. The hermaphrodite cream-white flowers appear in May, are insect pollinated, and go on to produce scarlet berries, which are often...

 s.str.). It contains a tetraploidal set of chromosome

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

s (2n=4x=68).

Sorbus rupicola, is rather similar to Sorbus aria

Sorbus aria

Sorbus aria , the Whitebeam or Common Whitebeam is a deciduous tree, compact and domed, with few upswept branches; it generally favours dry limestone and chalk soils. The hermaphrodite cream-white flowers appear in May, are insect pollinated, and go on to produce scarlet berries, which are often...

, but the lower third of the leaf has no teeth and the leaf is also rather longer and narrower.

External links

• Distribution map of S. rupicola. Naturhistoriska riksmuseet.