Current status
Ley`s whitebeam is an apomictic microspecies (a taxon arising through the asexual development of the maternal germ cells in the absence of fertilisation) and is thought to be derived from mountain ash (S. aucuparia) and rock whitebeam (S. rupicola). It is a distinctive large deciduous shrub or small tree which flowers in late May and early June. Fruits form in September, but are generally rather few in number. Germination of seed is also poor, with complete failure in some years. It is believed to be a light-demanding species which is probably unable to colonise densely shaded sites. It is also thought to be highly palatable to grazing stock at the seedling and sapling stage. Together with the apparent drought tolerance of mature trees, these factors probably explain its restriction to cliff habitats.
Ley`s whitebeam is endemic to south Wales, where it is known from only two localities on steep limestone cliffs. At one site 13 trees were recorded in 1983, mostly on partly wooded cliffs, while at the other three native trees have been reported, together with four trees which have become established from nursery grown saplings planted in 1962. Thus the total known wild population consists of a likely maximum of 16 established trees.
Ley`s whitebeam is now classified as Critically Endangered. It receives general protection under the Wildlife and Countryside Act 1981.
Current factors causing loss or decline
A number of ecological factors are thought to be involved in restricting the populations of Ley`s whitebeam, including grazing, disease, competition with introduced trees and shrubs, and seed productivity, which is probably low due to small population size and poor breeding success. Further research is required to unravel their relative importance.
Afforestation activities in the past may have destroyed potential colonisation sites.
Its preferred habitat of limestone cliff crevices and ledges is also scarce.
Current action
The two known sites for this species are protected as SSSIs.
Six nursery-grown saplings were planted at one of its sites by the Forestry Commission in 1962; four of these were still present in March 1996.
A specimen has been planted at the Forest Enterprise Garw Nant Visitor Centre.
A workshop was held at Wakehurst Place in April 1996 on the conservation status of whitebeams in the UK and a report is being produced.
Ex-situ populations are present in botanic gardens across the UK (including Westonbirt, Cambridge University and Ness Gardens).
Action plan objectives and targets
Maintain populations of Ley's whitebeam at its extant sites.
Where biologically feasible, enhance populations of Ley's whitebeam at its extant sites.
Proposed actions with lead agencies
Policy and legislation
Consider the inclusion of this taxon on Schedule 8 of the Wildlife and Countryside Act 1981, at the earliest possible opportunity. (ACTION: CCW, JNCC)
Site safeguard and management
Following the research outlined in 5.5.3, assess the need for site management at extant sites in order to create favourable conditions for growth and recruitment. If a management programme is considered necessary, it should be implemented by 2003. (ACTION: CCW, FE)
Seek opportunities for the creation of suitable habitats for Ley's whitebeam within currently afforested areas. (ACTION: CCW, FE)
Species management and protection
Coordinate existing programmes for the ex-situ conservation of Ley's whitebeam and seek to involve Wakehurst Place and the new National Botanic Garden of Wales. The material cultivated for any future introduction schemes should be genetically representative, as identified by the research outlined under 5.5.4. Priority should also be given to the maintenance of ex-situ populations of budded material and, if possible, seed from all existing wild individuals. (ACTION: CCW)
Undertake a survey to identify suitable sites away from (but close to) native localities where cultivated seedlings of Ley's whitebeam could be introduced in the event of wild populations being lost (although sites with S. minima or S. anglica should be avoided). This work should also serve to identify potential sites for natural recruitment. (ACTION: CCW)
Advisory
Advise landowners and managers of sites supporting native populations (and sites proposed for introduction), the importance of this taxon and any activities which may be damaging to it. (ACTION: CCW)
Future Research and Monitoring
Survey the two known sites for this species and map all surviving trees and any seedlings found. The sites should then be monitored frequently for at least 10 years and the need to protect individual seedlings reviewed at each visit. (ACTION: CCW)
Make a demographic assessment of each population, and use the findings to inform site and species management. (ACTION: CCW)
Assess potential factors which may be limiting the population size, including the effects of disease, herbivores and the spread of non-native trees, with a view to developing a beneficial management programme for both sites. (ACTION: CCW, FE)
Consider a genetic screening programme to add to existing data on intra- and inter-population genetic variation. (ACTION: CCW)
Communications and Publicity
Promote the development of existing visitor interpretation about endemic whitebeams at the Garw Nant Centre and seek to establish a similar educational resource at the new Welsh National Botanic Garden. (ACTION: CCW, FE)
Links with other action plans
None given.
Publication details
Originally published in: UK Biodiversity Group Tranche 2 Action Plans - Volume I: Vertebrates and vascular plants (June 1998, Tranche 2, Vol I, p245)