|Scientific Name:||Sorbus leyana Wilmott|
|Taxonomic Source(s):||The Plant List. 2016. The Plant List. Version 1.1. RBG Kew. Available at: http://www.theplantlist.org/.|
|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.|
|Red List Category & Criteria:||Critically Endangered D ver 3.1|
|Assessor(s):||Beech, E. & Rivers, M.C.|
|Reviewer(s):||Rich, T.C.G., Meyer, N. & Allen, D.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:|
|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.|
Native:United Kingdom (Great Britain)
|Range Map:||Click here to open the map viewer and explore range.|
|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|
|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:||Not found in trade.|
|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).|
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 13 December 2017.|