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Watsonia 27 : 301–313 (2009) SORBUS IN THE LOWER WYE VALLEY 301 The diversity of Sorbus L. (Rosaceae) in the Lower Wye Valley T. C. G. RICH* Department of Biodiversity & Systematic Biology, National Museum of Wales, Cardiff CF10 3NP L. HOUSTON School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG C. A. CHARLES 14 Bath Street, Frome, Somerset, BA11 1DN and A. C. TILLOTSON 69 Leighton Road, Southville, Bristol BS3 1NR ABSTRACT and documenting plant diversity’ under the Global Plant Conservation Strategy (Secretariat The diversity of Sorbus in the Lower Wye Valley on for the Conservation of Biodiversity 2002). the border between England and Wales is described. The Lower Wye Valley is a large, meander- Sixteen Sorbus taxa occur in the Lower Wye Valley, including two new species which are described as S. ing, north-south orientated valley c. 40 km long parviloba T. C. G. Rich and S. saxicola T. C. G. Rich. situated on the border between England and Diverse, important sites include the Symonds Yat to Wales extending from Ross-on-Wye to the Great Doward area, and the Pen Moel to Shorn Cliff Severn Estuary (Fig. 1). At the north end in the area. Overall, the Lower Wye Valley is the second Symonds Yat area between English Bicknor most diverse site for Sorbus in the British Isles. and Monmouth, the river meanders between There is evidence of a minor decline in diversity of a spectacular, large, wooded Carboniferous few species at a few sites. Limestone cliffs. The river then straightens running south through a broad valley over KEYWORDS : England, Wales, new species. sandstones, before entering a second series of meanders through another wooded Carbon- INTRODUCTION iferous Limestone gorge between Tintern and Bulwark. Three vice-counties are represented Britain, southern Scandinavia and the in the Lower Wye Valley; v.c. 34 West mountains of south-east to central Europe are Gloucestershire and v.c. 36 Herefordshire in the three main centres of diversity of Sorbus L. England, and v.c. 35 Monmouthshire in Wales. (Rosaceae) in Europe. Within Britain, the six The natural history of the valley has recently key areas of diversity are the North Devon and been described by Peterken (2008). Significant North Somerset coast, Cheddar Gorge, Avon sites are protected as Sites of Special Scientific Gorge, the Lower Wye Valley, the Brecon Interest and Special Areas for Conservation, Beacons and Arran. A few other areas such as and it is an Area of Outstanding Natural Morecambe Bay, the Mendips and South Beauty. Devon also support some endemics. In this In 1999, T. Rich began a project looking at paper an account of the diversity and diversity and evolution in Sorbus and visited distribution of taxa within one of these, the many areas in the Wye Valley. In 2000, the Lower Wye Valley, is given based on surveys Wye Valley was included in the European carried out between 1999 and 2006, with the Ravine Wood Life Project as part of the Natura description of two new species. The data 2000 initiative, and English Nature (now contribute towards Target 1 ‘Understanding Natural England) commissioned abseil access *e-mail: [email protected] 302 T. C. G. RICH, L. HOUSTON, C. A. CHARLES AND A. C. TILLOTSON FIGURE 1. Location of Sorbus sites surveyed in the Lower Wye Valley. SORBUS IN THE LOWER WYE VALLEY 303 surveys of Sorbus on the major cliffs to provide Collection of voucher specimens concen- information for conservation and management trated on the rarer or more difficult to identify (Houston et al . 2001, 2002, 2003, 2004). These taxa. Identifications of voucher material were abseil surveys provided a wealth of new Sorbus confirmed by T. Rich, with other material material, which significantly augmented what determined in the field. The 755 specimens could be collected from cliff tops. The data collected are deposited in the National Museum from both these studies are combined in this of Wales ( NMW). paper to give an overview of the diversity of Most of the taxa found during the surveys Sorbus in the Wye Valley. were allocated to existing taxa, but the situation with the S. eminens E. F. Warb. group and S. porrigentiformis E. F. Warb. group was more METHODS complex (see also Proctor & Groenhof 1992). In the S. eminens group, plants with orbicular MORPHOLOGY AND DESCRIPTIONS OF NEW SPECIES leaves matching the widespread Avon Gorge- Broad leaves from the short, vegetative shoots Mendips form were called S. eminens sensu in sunlit situations, excluding the oldest and stricto, and plants with leaves subrhombic in youngest leaf (Aas et al . 1994), were measured outline with deeper teeth as S. eminentiformis on herbarium material of the two new taxa in T. C. G. Rich, following Rich & Proctor NMW. Fruits were measured on fresh material, (2009). Proctor & Groenhof (1992) noted that and the colours matched against the Royal these two species probably belonged to Horticultural Society colour charts (Royal separate taxa, and regarded all the Wye Valley Horticultural Society 1966). S. ‘eminens’ as belonging to S. eminentiformis . Conservation status assessments were made Our more extensive collections coupled with for the new species following the IUCN (2001) analysis of the plastid DNA (Chester et al. guidelines. 2007) indicate both taxa are present throughout the valley. Warburg’s type specimen was HISTORICAL INFORMATION AND SURVEYS collected from Offa’s Dyke, Tidenham, v.c. 34 Historical information was compiled from West Gloucester-shire ( BM ; Warburg 1952, herbaria ( BM , BRISTM , GLR , K , NMW), the 1957) but is a poor specimen which is not voucher material of Proctor & Groenhof (1992) clearly referable to either form, but he stated now held at NMW, and from the literature (e.g. that the description related to plants from the Evans 2007; Riddelsdell et al. 1948). Avon Gorge and Lower Wye Valley. However, Surveys were carried out between 1999 and an unusual feature of Warburg’s description 2008, mainly in the autumn when fruits were was that his S. eminens had fruits up to 2 cm present helping identification. Two main long which were longer than wide; this does methods were used: not equate to either our observations of S. eminens as currently interpreted, or those of 1. ‘Look-see’ surveys (Rich et al . 2005) were Proctor & Groenhof (1992). Searches of Offa’s carried out by walking along cliff tops and Dyke at Tidenham have failed to reveal any sometimes cliff bottoms, and noting taxa plants with such long fruits, but several plants seen without consistently counting exact were found at Shorn Cliff immediately below numbers of each species. Some material Offa’s Dyke with long fruits which had leaves was collected using a long-handled pruner. like S. eminens but not identical ( NMW); this 2. Abseil or rope access surveys were carried problem is best dealt with by amending the out by abseiling down rock-faces in a series description of S. eminens sensu stricto to of ‘drops’ along the cliffs at intervals of 3– having fruits wider than long. 10 m according to the frequency of Sorbus Warburg (1952, 1957) also described S. porri- or presence of hazards such as loose rock. gentiformis from Offa’s Dyke at Tidenham, Samples were collected directly from the and this probably represents the widespread, ropes, or sometimes using a long-handled lowland form (Proctor & Groenhof 1992). pruner. Numbers of each species were Again we have failed to find any plants which counted, but due to practicalities of clearly match the type, though at least one tree identification some counts are minima. In remains with relatively narrow leaves on the certain areas only quicker cliff-top or cliff- banks of Offa’s Dyke (this does not have base ‘look-see’ surveys were carried out. leaves as narrow as S. saxicola described below Full details are given in the survey reports however). As Warburg (1957) pointed out, (Houston et al . 2001, 2002, 2003, 2004). plants from different locations differ, and we 304 T. C. G. RICH, L. HOUSTON, C. A. CHARLES AND A. C. TILLOTSON have recorded plants with small, obovate 4. Wintour’s Leap (ST542964), v.c. 34 leaves and fruits wider than long as S. porri- The huge, quarried, 100 m high, NW- to gentiformis sensu stricto, and similar plants SW-facing cliffs of Wintour’s Leap cont- with larger leaves of more variable shape as S. inue north for c. 500 m from Woodcroft porrigentiformis sensu lato. Quarry to Lancaut. They have secondary With both the S. eminens group and S. woodland over quarry spoil below, and porrigentiformis group we suspect that there private gardens above with a short section are a significant number of hybrids with S. aria of public footpath. The cliffs and woods are in the Wye Valley, as also recently reported for part of Gloucestershire Wildlife Trust’s the Avon Gorge (Rich et al. 2009); con- Lancaut Nature Reserve. firmation of these will have to await DNA The cliffs were surveyed in a series of analysis. Plants from Symonds Yat discussed rope drops in autumn 2003 (Houston et al. as similar to S. graeca (Spach) Kotschy by 2004) and using ‘look-see’ in 2006. Proctor & Groenhof (1992) are here included in S. porrigentiformis sensu lato, and are 5. Ban-y-gor Rocks – Cockshoot (ST547972), probably also locally derived apomictic hybrids v.c. 34 of S. aria and S. porrigentiformis . Ban-y-gor Rocks and Cockshoot form a The sites surveyed are as follows, ordered series of crags about 1 km long with a N- to first by vice-county and second from south to WNW-aspect. The western crags are 15–20 north with approximate grid references (Fig.