Rhytidiadelphus Subpinnatus in Wales

Article Rhytidiadelphus subpinnatus in Wales

v R. subpinnatus. Sam Bosanquet

hectads and the vice-counties of Breconshire Rhytidiadelphus and Glamorgan. Tetrad recording in Pembroke- shire in early 2008 produced a colony in the Gwaun Valley, whilst a serendipitous stop by subpinnatus in Wales the Afon Eden in Meirionydd revealed a new population about 20 km north of the known Rhytidiadelphus subpinnatus is one of a small number of site at Torrent Walk. A family walk near Brechfa turned up a fourth Carmarthenshire bryophytes that are much less common in Britain than in continental population just before Christmas 2008. These Europe. Like Homomallium incurvatum (Blockeel, 2007), another of records combine with lost sites in Cwm Nantcol, Meirionydd and near Abergorlech, these British rarities, its identification features seem to have been Carmarthenshire, to give four areas of Wales forgotten by a generation of bryologists. Sam Bosanquet and where R. subpinnatus grows or grew. From south- Graham Motley remind us of this species’ characteristics west to north-east these are: 1 Cwm Gwaun, Pembrokeshire (SN0233– and report some recent records in Wales. SN0333) (v.-c. 45). This is the smallest colony in Wales. Six patches grow on a bank by the he Red Data Book (Church et al., Dixon (1924) described R. subpinnatus (as Recent records footpath that runs along the bottom of Allt 2001) reports just two extant colon- R. squarrosus var. calvescens) as ‘very rare’ and During tetrad-bashing for The Mosses and Pontfaen, which is set back from the Afon ies of Rhytidiadelphus subpinnatus mentions a specimen from Dolgellau (Dolgelly Liverworts of Carmarthenshire in 2005, SDSB Gwaun by about 10 m. and suggests that there has been a sic.). The Atlas (Hill et al., 1994) shows records found a large colony of R. subpinnatus in 2 Afonydd Tywi (SN5019–SN5020), Cothi significant decline in this species, from 12 British hectads (10x10 km squares) – woodland by the Afon Tywi in Carmarthenshire (SN5328 & SN5833) & Sawdde (SN7224– Tespecially in northern England. Only populations mostly in north-west England, with three in (Bosanquet et al., 2005). Shortly afterwards, SN7323), Carmarthenshire (v.-c. 44). Three at Torrent Walk, near Dolgellau in Meirionydd Wales and one in Herefordshire – and one Irish GSM found another Carmarthenshire popu- river valleys in eastern Carmarthenshire. The (v.-c. 48) (Holyoak, 2001) and at Roeburndale hectad. Its European distribution is Circumpolar lation more than 20 km to the east in the Sawdde Tywi colony comprises at least 66 patches in in the north-eastern part of West Lancashire Boreal-montane (Hill & Preston, 1998), which Gorge, followed by the first Breconshire record steep riverside woodland at Allt Ffinnant. The (v.-c. 60) had been seen since 1950. Atmospheric is somewhat at odds with its essentially lowland in the Nedd Fechan valley near Ystradfellte. western Cothi colony, near Horeb, was spotted pollution was blamed for this decline (Hodgetts British distribution with, until recently, no con- Subsequent recording and survey work in the in late 2008 and is made up of just four patches; in Hill et al., 1994) and was linked to a general firmed records from Scotland. The 2007 Scottish Nedd and Mellte Valleys has revealed this to the eastern Cothi colony, at Abergorlech, was decline in Rhytidiadelphus species in polluted colony, in southern Stirlingshire, is at 100 m be a hotspot for the species, with at least three found by E.W. Jones in 1945 and has not been districts. altitude in the central belt, so is also lowland. separate subpopulations split between three relocated despite four specific searches, the last

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v R. subpinnatus. Sam Bosanquet

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in late 2008. The Sawdde colony is widespread 9 to be because British bryologists have come between Turkey Cottage and Pont ar Llechau 8 to think of R. subpinnatus as looking like a in mossy turf on ledges by the river. The Tywi 7 small R. squarrosus, rather than having its own 6 and Sawdde colonies have the largest number 5 distinctive appearance. Dixon (1924) points out of patches known in Wales and the Sawdde 4 the ‘great resemblance in its strongly marked forms 3 colony is the only one where non-hybrid 2 to Hylocomium brevirostre’, which seems to sporophytes have been found (see Ecology and 1 have been forgotten in subsequent decades and 0 status, below). 9 was not mentioned by Smith (1978, 2004). Its 3 Dyffrynnoedd Nedd a Mellte (Neath 8 distinctive appearance – with wide, short leaves Waterfalls area), Breconshire (v.-c. 42) & 7 6 on most branches, but strongly squarrose leaves Glamorgan (v.-c. 41) (SN8908, SN9108, 5 at the shoot tip and on some branch tips – makes SN9110). An extensive area of oak and ash 4 plants of R. subpinnatus look like Loeskeobryum 3 woodland along four main river valleys, with 2 (=Hylocomium) brevirostre but with R. squarrosus colonies of R. subpinnatus recorded in two 1 tips (see photos). Closer examination reveals 0 of these. The colony by the Nedd Fechan 9 squarrose stem leaves, which are like those of above Pont Melin-Fach consists of 12 patches 8 R. squarrosus but spread out from the base, rather 7 growing on a steep bank by the main footpath than clasping the stem. This makes the red stem in oak woodland. Further down the valley, 7890123456789012345 stand out more than that of R. squarrosus, and near Pontneddfechan, below where the Afon n Distribution of R. subpinnatus in Wales plotted at the also reveals a lack of paraphyllia, distinguishing R. Pyrddin joins the Nedd Fechan to form 5-km level. Pale blue dots, pre-1970 records; dark blue subpinnatus from L. brevirostre. Individual stems the Afon Nedd, R. subpinnatus grows on dots, post-1970 records. Sam Bosanquet are, as the name suggests, subpinnate, although both the Breconshire and Glamorgan sides often with irregularly branched sections. The of the river, again immediately adjacent to from which R. subpinnatus has been known overall colour of dry patches tends to be pale the main footpaths and in oak woodland. for longest. It was collected several times from green, sometimes with greyish or even salmon The Glamorgan colony consists of a single Cwm Artro and Cwm Nantcol (SH6427) pink tones; with moist plants the stems appear patch with some scattered shoots, but on the between 1904 and 1912, but has not been bright red. Forms of R. squarrosus in which Breconshire side more than 15 patches have seen there since. Holyoak (2001) revisited the branch leaves are not particularly squarrose are been noted. A further colony occurs scattered well-known site at Torrent Walk (SH7518), sometimes encountered. These plants often look along the eastern side of the Afon Mellte below where R. subpinnatus was discovered in 1876, rather etiolated, with individual branches rather Craig y Ddinas in both oak and ash woodland. and reported it ‘on a bank above the Torrent thin, rounded and tapering towards the tip, unlike Here, 14 patches occur alongside the footpath Walk’. SDSB stopped by the Afon Eden north the more robust and sometimes complanate n Habit and close-ups of R. subpinnatus. Sam Bosanquet and also in a less vulnerable position high of Ganllwyd (SH7226) during a journey to appearance of R. subpinnatus branches. above the path. Most of the colonies in the north Wales and found frequent patches on ‘Waterfalls’ area have been casual finds whilst flat ground on the east bank of the river. Ecology and status rutabulum, Cirriphyllum piliferum, Eurhynchium visiting the site for reasons other than for All of the Welsh colonies of R. subpinnatus are striatum, Kindbergia praelonga, R. loreus, R. purely bryological survey – it seems likely Identification in steep-sided, wooded river valleys in hilly triquetrus, Thuidium tamariscinum and the that a targeted survey could find this species Smith (1978) says that about half the 20th districts. Patches up to 100x80 cm in size liverwort Plagiochila asplenioides. All colonies to be more widespread throughout these river century specimens collected as R. subpinnatus grow on banks or over rocks or well-rotted are on the floor of broadleaved woodlands with valleys. were R. squarrosus, and it is clear that there tree stumps, sometimes forming mounds that ash (Fraxinus excelsior), hazel (Corylus avellana) 4 Dolgellau & Rhinogs (SH62–SH72), Meiri- has been considerable confusion over the are intermixed with other bulky pleurocarpous and oak (Quercus sp.) as the principal trees. onydd (v.-c. 48). This is the area of Wales identification of R. subpinnatus. This appears mosses. Typical associates include Brachythecium Three distinct niches on the woodland floor

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are exploited: flat ground immediately adjacent shift from a riparian woodland ground layer in are made aware of the presence of R. subpinnatus, to a river, where flooding is likely to be annual; which R. subpinnatus can grow, to a flora more its continued existence in Wales seems assured. steep ground above the river, with records up akin to a pasture, which is unsuitable for this rare It seems very unlikely that R. subpinnatus to 20 m above the river level; and steep banks moss. It is worth noting that the two strongest should be relatively widespread in Wales but by footpaths, which tend to be just above populations, by the Afonydd Tywi and Sawdde, restricted to a single site in England. Perhaps the flood zone. The last of these niches is are in narrow strips of woodland between the English bryologists could seek it specifically highly vulnerable to any footpath diversions river and a road, which have probably not seen a in humid, wooded river valleys, bearing its or widening works. sheep for decades. resemblance to Loeskeobryum brevirostre in mind. TheAtlas (Hill et al., 1994) says that the sporo- The other Cothi Valley site, where E.W. phytes of R. subpinnatus are unknown in Britain. Jones found R. subpinnatus in 1945, has been Sam D.S. Bosanquet Holyoak (2001) reported a small, shrivelled extensively modified by forestry operations. Cnwc y Llwyn, Brechfa, Carmarthen, capsule at Torrent Walk, where all the R. sub- The north bank is now largely occupied by an Carmarthenshire SA32 7QR pinnatus population is female. The nearest male ash plantation, the floor of which is strewn with Rhytidiadelphus was R. loreus, and Holyoak branch debris from a recent thinning, whilst Graham S. Motley suggests this was most probably the male parent the south bank has been coniferized apart from St Helen’s Road, Abergavenny, of the therefore hybrid sporophyte. However, a narrow strip by the river. Two visits to each Monmouthshire NP7 5UU GSM found several patches of R. subpinnatus in bank have failed to produce R. subpinnatus, and Cwm Sawdde with healthy looking sporophytes it seems to have disappeared, perhaps because of References that had dehisced by mid-April 2005 (Bosanquet changes in humidity or light levels. Blockeel, T.L. (2007). The status and habitat ofHomomallium et al., 2005). Male plants were present both there Recent records of R. subpinnatus in four widely incurvatum in the north of England. Field Bryology 91, and at the other extant Carmarthenshire site by separated areas of Wales suggest that the decline 2–7. the Afon Tywi. Given the strength of the Cwm suggested by the Red Data Book and the Atlas may Bosanquet, S.D.S., Graham, J.J. & Motley, G.S. (2005). The Sawdde population and the presence of both not have been as dramatic as was first thought. Mosses and Liverworts of Carmarthenshire. Dingestow: Private male and female plants, it seems clear that the Indeed, it seems highly likely that the loss of publication. sporophytes there are not of hybrid origin, so knowledge of the appearance and specific habitat Church, J.M., Hodgetts, N.G., Preston, C.D. & Stewart, N.F. they represent the first confirmed fruiting of of R. subpinnatus in Britain caused this apparent (2001). British Red Data Books Mosses and Liverworts. R. subpinnatus in Britain. decline, as was the case with Homomallium Peterborough: Joint Nature Conservation Committee. The main threats to R. subpinnatus appear to incurvatum (Blockeel, 2007). Nevertheless, it is Dixon, H.N. (1924). The Student’s Handbook of British Mosses. be livestock grazing and forestry works. The last far from ubiquitous in Wales and is likely to be a Eastbourne: V.V. Sumfield. colony to be discovered, by the Afon Cothi near genuinely scarce, if not rare, species in Britain as a Hill, M.O. & Preston, C.D. (1998). The geographical Horeb, is in a typical situation on narrow river whole. SDSB consciously searched for it for 3 relationships of British and Irish bryophytes. Journal of Bryology 20, 127–226. flats at the foot of a very steep wooded slope, years in Pembrokeshire before finally discovering Hill, M.O., Preston, C.D. & Smith, A.J.E. (editors) (1994). but the ground is much grassier than would be a colony, and several searches in apparently suit- Atlas of the Bryophytes of Britain and Ireland, Vol. 3. Mosses expected. R. squarrosus is abundant in this grassy able habitat in Cardiganshire have failed to pro- (Diplolepideae). Colchester: Harley Books. turf, mixed with more typical woodland mosses, duce any colonies. Remarkably, all of the Welsh Holyoak, D.T. (2001). A hybrid sporophyte on Rhytidiadelphus such as Atrichum undulatum, C. piliferum, R. populations of R. subpinnatus are protected by subpinnatus. Bulletin of the British Bryological Society 76, loreus, R. triquetrus and T. tamariscinum, and SSSIs, all but one of which were designated 56–58. R. subpinnatus is limited to four patches. This before the species was found, and several of which Smith, A.J.E. (1978). The Moss Flora of Britain and Ireland. wood is regularly sheep-grazed, which is thought include bryophyte assemblages as qualifying Cambridge: Cambridge University Press. n Habitats of R. subpinnatus in Nedd Fechan (top) and to encourage grass growth and R. squarrosus, features. Providing landowners and people Smith, A.J.E. (2004). The Moss Flora of Britain and Ireland, 2nd the Cwm Gwaun valley (bottom). Sam Bosanquet and it seems as though this is causing an active maintaining footpaths in these valley woodlands edn. Cambridge: Cambridge University Press.

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