Sorbus leyana 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Rosales Rosaceae

Scientific Name: Sorbus leyana Wilmott
Common Name(s):
English Ley's Whitebeam, Ley's Whitebeam
Taxonomic Source(s): The Plant List. 2016. The Plant List. Version 1.1. RBG Kew. Available at:
Taxonomic Notes: The species is an apomictic product of a cross between S. aucuparia L. and S. rupicola (Syme) Hedl or S. porrigentiformis Warb. sensu lato.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2017
Date Assessed: 2015-11-13
Assessor(s): Beech, E. & Rivers, M.C.
Reviewer(s): Rich, T.C.G., Meyer, N. & Allen, D.J.
Contributor(s): Wigginton, M.J.
Sorbus leyana is a shrub or small tree, restricted to two locations in Breconshire, Wales. The species is assessed as Critically Endangered (CR D) as the population contains only 11 mature individuals. It is threatened by grazing, low reproduction and limited habitat (Rich et al. 2010). Habitat management could encourage further regeneration. The species is also severely range restricted and there is a decline in the number of mature individuals.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This Welsh endemic species is found in only two adjacent sites (Penmoelallt Forest Nature Reserve and Darren Fach) in Breconshire, Wales (Rich et al. 2010). Both the area of occupancy (AOO) and the extent of occurrence (EOO) are estimated at 4 km2.
Countries occurrence:
United Kingdom (Great Britain)
Additional data:
Estimated area of occupancy (AOO) - km2:4Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:4
Continuing decline in extent of occurrence (EOO):No
Number of Locations:2
Lower elevation limit (metres):340
Upper elevation limit (metres):360
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:At Darren Fach, in 2004 only eight trees remained of the 15-20 shrubs reported by Ley in 1901 (G. Motley pers. comm. 2016). At Penmoelallt Forest Nature Reserve, in 2004 there were three mature trees and six saplings as well as six of seven trees planted in 1963 (Rich et al. 2005). The estimated number of mature individuals does not include the planted trees as it is not known if they have yet produced viable offspring. The Darren Fach population is decreasing whereas the Penmoelallt population has seen some regeneration under one tree (Rich et al. 2005, T. Rich pers. comm. 2016).

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:11Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:A shrub or small tree to at least 10 m, Sorbus leyana is found on wooded carboniferous cliffs, where the trees can reach the light. They appear to reproduce sporadically with an average pollen viability of 24% (Rich et al. 2010).
Continuing decline in area, extent and/or quality of habitat:Unknown

Use and Trade [top]

Use and Trade: Not found in trade.

Threats [top]

Major Threat(s): It is thought it is rare due to its low levels of reproduction, limited habitat and possibly a relatively recent origin. Grazing is likely to prevent this species spreading to grassland areas (Rich et al. 2010). Encroaching woodland at one site is causing shading that is preventing flowering and fruiting (T. Rich pers. comm. 2016).

Conservation Actions [top]

Conservation Actions: Both locations are within Sites of Special Scientific Interest and a small number of plants raised from seed have been incorporated into the population. Regeneration under one tree at Penmoelallt is thought to have occurred because another large tree was lost resulting in an increase of light; coppicing could bring about similar increases in Darren Fach (Rich et al. 2005).

The species has been assessed as Critically Endangered for Great Britain (Cheffings and Farrell 2005) and as Critically Endangered globally in Oldfield et al. (1998).

It is listed as a UK BAP priority vascular plant species (JNCC 2010) and is also a Welsh Section 42 species. It was under conservation at the National Botanic Garden of Wales, which recently disposed of most their living collection. Sorbus leyana is reported as held in 11 ex situ collections (BGCI 2015) and is recorded as present in an ex situ seed bank collection (ENSCO 2015).

Citation: Beech, E. & Rivers, M.C. 2017. Sorbus leyana. The IUCN Red List of Threatened Species 2017: e.T34723A80736437. . Downloaded on 23 April 2018.
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