A NEW CRUSTOSESTEREOCAULONFROM THE MOUNTAINS OF SCOTLAND AND WALES

Lichenologist 28(6): 513–519 (1996)

A NEW CRUSTOSE STEREOCAULON FROM THE MOUNTAINS OF SCOTLAND AND WALES Alan M. FRYDAY* and Brian J. COPPINS‡

Abstract: The new combination Stereocaulon plicatile (Leight.) Fryday & Coppins is made for a previously enigmatic crustose lichen with submuriform ascospores; the basionym, Lecidea plicatilis Leight., was previously misapplied to a norsticticacid containing species of Rhizocarpon. The systematic position of the crustose Stereocaulon leucophaeopsis group is discussed. ? 1996 The British Lichen Society

Introduction For some years we have been aware of an enigmatic crustose lichen with soredia, Porpidia-type asci and submuriform ascospores occurring in damp corries and above areas of prolonged snow-lie in the Scottish Highlands. We then realized that it belonged in the Stereocaulon leucophaeopsis group, being close to S. tornense, differing mainly in having submuriform rather than 3-septate ascospores. During a study of the non-yellow species of Rhizocarpon occurring in the British Isles, the first author discovered that the type specimen of Lecidea plicatilis Leight., described from a specimen collected in North Wales and referred to Rhizocarpon by A. L. Smith, was a specimen of this species. The necessary new combination is made, a full description provided and the systematic position of the S. leucophaeopsis group discussed.

The Species Stereocaulon plicatile (Leight.) Fryday & Coppins comb. nov. Lecidea plicatilis Leight., Ann. Mag. nat. Hist., ser. 4, 4: 201 (1869)—Rhizocarpon plicatile (Leight.) A. L. Sm., Monogr. Brit. Lich. 2: 197 (1911). Type: Wales, [V.C. 48, Merioneth] Cader Idris, Llyn-y-Cae, on schistose rocks, 1869, W. A. Leighton (BM—holotype).

(Fig. 1) Thallus crustose, thin (up to 0·2 mm thick), rimose to areolate, sorediate. Areoles, when discrete, c. 0·2–0·6 mm wide, confluent to scattered, plane to slightly convex, whitish to grey, matt to slightly glossy, only rarely a few with darker centres. Cortex 28–70 ìm thick, hyaline, densely encrusted with minute crystals (mostly K+ dissolving yellow); hyphae c. 2·5–3 ìm (in K); epinecral layer often present, up to 12 ìm thick. Soralia 0·2–0·3(–0·4) mm diam., *Department of Landscape, University of Sheffield, Sheffield S10 2TN, UK. Present address: 110 Eastbourne Road, Darlington DL1 4ER, UK. ‡Royal Botanic Garden, Inverleith Row, Edinburgh EH3 5LR, UK. 0024–2829/96/060513+07 $25.00/0

? 1996 The British Lichen Society

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A

C

B

F. 1. Stereocaulon plicatile (Ben Ghlas, 23 x 1989, Fryday, E). A, Ascus tips in K/I (stippling denotes amyloid parts); B, Ascospores; C, Paraphyses apices (stippling denotes coloration, not ornamentation). Scales=10 ìm (shorter scale for asci only).

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arising from cracks in the areoles, discrete to becoming confluent, pale green to bluish green or brown. Soredia c. 25–50 ìm diam., greenish white, but surface soredia often brown tinged; surface hyphae brown-walled (pigment K", N"). Photobiont ?trebouxioid, cells 6–11 ìm diam. or ellipsoid and 7–14 # 4–8 ìm. Cephalodia absent. Apothecia (0·2–)0·6–1·2(–1·6) mm diam., &sessile, blackish with a brown tinge (especially when moistened); disc flat to slightly convex, epruinose; margin usually distinct but becoming reflexed or folded in old apothecia, c. 0·1 mm thick, smooth. Hymenium (80–)90–100(–110) ìm tall, hyaline, I" but I+ blue around the asci; epithecium 15–18 ìm tall, reddish brown, K", N". Paraphyses mostly simple, only a few occasionally branched or anastomosed, 1·3–1·5 ìm thick in mid-hymenium; apices swollen to 3–4 ìm, with distinct, dark brown apical caps (Fig. 1C). Asci clavate-cylindrical, (65–)70– 95 # 15–25 ìm, (4–)8-spored, apical dome I+ blue with dark blue, axial tube (Porpidia-type; Fig. 1A). Ascospores 20–32 # 10–15 ìm, variously ovoid, ellipsoid or fusiform, hyaline, submuriform to muriform with 3–7 transverse septa and 1–6 transverse cells with 1 (very rarely 2) longitudinal septum, without a distinct perispore (Fig. 1B). Subhymenium often difficult to distinguish from hypothecium, but usually paler and 15–30 ìm tall. Hypothecium 40–70 ìm tall reddish brown, K+ orange-red tinge. Excipulum distinct, running beneath the hymenium almost to the centre of the apothecium, dark reddish brown within, somewhat paler towards the edge, formed of dense, radiating, strongly conglutinated hyphae, 2·5–3·5 ìm thick, with a rather thick wall and a narrow lumen; apical cells at edge of excipulum swollen to 4 ìm, often with distinct apical caps (as in paraphyses). Conidiomata pycnidia, immersed in the areoles, c. 60–70 ìm diam., dark reddish brown, &globose. Conidiogenous cells sessile or on once-branched conidiophores, forming mainly acrogenous (rarely also pleurogenous) conidia. Conidia (spermatia) 14–18(–22) # 0·5–0·7 ìm, hyaline, filiform, curved. Chemistry: Cortex K+ yellow, PD" or PDf+ yellow; soralia K+ yellow, PD+ orange; medulla K+, or Kf+ yellow, PD"; all parts C", KC", UV". Atranorin and stictic acid by TLC. Habitat and distribution: Stereocaulon plicatile is known only from high altitude sites (mostly over 800 m) in the British Isles, where it is occasionally locally frequent on siliceous rocks and pebbles. All the Scottish collections are from damp habitats associated with areas of late snow-lie; either on &vertical rocks in north-facing corries or on stones and pebbles in soil near cornice snow beds. It favours the former habitat in the drier, eastern mountains, and the latter in the more oceanic, western mountains. The species has not yet been found on rocks below corrie snow beds, where S. tornense is often abundant. It appears that the much wetter conditions that prevail in this habitat favour S. tornense over S. plicatile, which occurs in somewhat better drained conditions. The recent Welsh collection (Fryday 4671) is somewhat anomalous in that, although it is from small pebbles, these are embedded in a Festuca grass heath. It is assumed that the grass sward holds sufficient moisture to provide the dampness required by the lichen.

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T 1. Data from three 2 # 2 m quadrats from above an area of prolonged snow-lie on Creag Meagaidh at c. 1000 m alt. Cover values are according to the Domin scale Distance from upper edge of snow-bed (m) Aspect Slope Cover (%) Lichens Bryophytes Vascular plants Rock Average size of rocks (cm)

18 0) (N) 25)

26 0) (N) 20)

12 45 60 15 20 (plus 2 boulders at c. 60)

20 40 70 20 20

<1 15 85 10 5–10

7 4 1 1 1 2 2 · · · · ·

9 5 5 1 1 2 2 2 · · · ·

6 3 4 1 7 · · · 4 3 1 1

Polytrichum sexangulare Moerckia blyttii Rhytidiadelphus loreus Kiaeria starkei Racomitrium lanuginosum Polytrichum alpinum Anthelia sp. Dicranum scoparium

5 2 1 5 1 · · ·

3 1 1 2 2 2 · ·

1 1 1 · · 4 1 3

Stereocaulon plicatile S. tornense Rhizocarpon ‘colludens’ Porpidia crustulata Micarea paratropa Cladonia bellidiflora Lepraria neglecta Verrucaria margacea Frutidella caesioatra Miriquidica griseoatra Rhizocarpon lavatum Lecidea pycnocarpa Cladonia chlorophaea Lecidella bullata Lecanora leptacina Micarea lignaria

1 3 3 3 1 1 1 1 1 1 1 1 1 1 1 1

2 2 2 3 1 2 1 · · · · · · · · ·

1 1 · · · · · · · · · · · · · ·

Species Deschampsia cespitosa Carex bigelowii Deschampsia flexuosa Huperzia selago Nardus stricta Saxifraga stellaris Rumex acetosa Agrostis capillaris Galium saxatile Viola palustris Gnaphalium supinum Athyrium distentifolium

12 0) (N) 27)

Table 1 continued on next page

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T 1. Continued Species Porpidia contraponenda Cetraria islandica Micarea turfosa Trapelia obtegens· Omphalina ericetorum Trapelia mooreana Pertusaria oculata Trapeliopsis gelatinosa Micarea leprosula Cladonia pyxidata Ionaspis odora Lecidea lithophila

· · · · · · · · · · · ·

1 1 1 2 1 1 2 1 1 1 · ·

2 2 · · · · · · · · 1 1

The quadrats at 12 and 18 m from the upper edge of the snow-bed belong to U13 Deschampsia cespitosa–Galium saxatile grassland, and that at 26 m to U7 Nardus stricta–Carex bigelowii grass-heath (Rodwell 1992).

Stereocaulon plicatile is known from montane areas across the British Isles and is almost certainly present in other mountainous areas. It should, in particular, be looked for in Scandinavia. Associated species identified on specimens of S. plicatile include Cladonia subcervicornis, Frutidella caesioatra, Polyblastia gothica, Porpidia macrocarpa, Trapelia placodioides and Andreaea sp. In addition, data from three 2 # 2 m quadrats containing S. plicatile on Creag Meagaidh (see specimens examined below) are given in Table 1. Remarks: Species of the genus Stereocaulon characteristically have their apothecia borne on pseudopodetia, and in rare, neotinic forms the apothecia arise from the basal squamules (basal phyllocladia) (Jørgensen & Jahns 1987). The pseudopodetia, or occasionally basal phyllocladia, of at least some specimens of most species, bear well-defined cephalodia. The apothecia of Stereocaulon have hitherto been reported to have a hyaline hypothecium. However, Stereocaulon plicatile, S. leucophaeopsis (Nyl.) P. James & Purvis and S. tornense (H. Magn.) P. James & Purvis seem to comprise a distinct group. They each lack pseudopodetia, with their apothecia developing from between the thalline areoles, and have a dark brown hypothecium. Furthermore, they lack cephalodia, although loosely associated colonies of cyanobacteria are often present, especially in S. tornense and S. leucophaeopsis (Jørgensen & Jahns 1987; Jahns et al. 1995). This combination of characters may well prove to warrant taxonomic recognition for this small group at sectional, subgeneric or even generic rank. The monotypic genus Muhria P. M. Jørg. is also a crustose member of the Stereocaulaceae, but has a very different ascomatal ontogeny, whereby the apothecia are initially globose with a star-like opening, later becoming urceolate (Jørgensen & Jahns 1987). The apothecia of Muhria urceolata P. M. Jørg., Stereocaulon leucophaeopsis and S. tornense have been shown to develop from a basal layer of the thallus that often contains cyanobacteria (Jørgensen & Jahns 1987; Jahns et al. 1995). In S. plicatile we have not detected such a cyanobacterial layer, which is

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perhaps lacking, or very poorly developed, owing to the generally more freely draining nature of its substrata. The areoles of these crustose species of Stereocaulon could be regarded as ‘ basal phyllocladia ’, and have alternatively been neutrally termed as ‘ scales ’ by Jahns et al. (1995). The upper cortex at the centre of the areoles of S. leucophaeopsis is usually distinctly hyaline, similar in structure to the phyllocladia of S. vesuvianum. Areoles with hyaline centres are also found in S. tornense, although little evident in some collections, but are only rarely observed in S. plicatile. These ‘ hyaline centres ’ give a darker appearance to the centres of the areoles in surface view ( # 10 lens), owing to the darker photobiont layer being visible, and their biological significance has been discussed by Jahns et al. (1995). Stereocaulon plicatile is unique within its genus in having submuriform to muriform ascospores, although muriform ascospores are characteristic of the segregate, Southern Hemisphere genus Argopsis Th. Fr. (Lamb 1974). However, the three species of this latter genus all have well-developed pseudopodetia. Apart from the distinct difference in ascospores, S. plicatile and S. tornense are virtually anatomically morphologically and chemically indistinguishable, although from the specimens available, S. plicatile tends to have a thinner, less well-developed thallus with more dispersed, flatter areoles. In both S. plicatile and S. tornense, PD tests on thallus sections indicate that stictic acid (PD+ orange) is confined to the soralia; the medulla of nonsorediate areoles is always PD". Even when sterile, S. leucophaeopsis can be chemically distinguished from both species: all parts PD", containing atranorin and lobaric acid. The true identity of the type of Rhizocarpon plicatile was revealed during the course of a study of British non-yellow species of Rhizocarpon. The name R. plicatile has evidently been misapplied (by e.g. Purvis et al. 1992) to a member of the ‘ R. obscuratum ’ group that contains norstictic acid, the correct name for which is probably R. rubescens Th. Fr. However, this may be no more than a chemical race of R. reductum Th. Fr. (Fryday 1996). This problem will be addressed further in a forthcoming paper (Fryday, in prep.). Selected additional specimens examined: Scotland: V.C. 88, Mid-Perthshire: Ben Lawers range: crags to N of Ben Ghlas, 27/625405, c. 1000 m, on vertical acid rocks, 25 viii 1989, Fryday (E, M); Ben Lawers range, Ben Ghlas, 27/624405, alt. c. 1020 m, on acid rocks subjected to late snow-lie, 23 x 1989, Fryday (E); Ben Ghlas, 27/62.40, c. 1050 m, on acid rock, &subjected to late snow-lie, x 1989, Fryday (E, hb. Fryday); Beinn Heasgarnich, Coire Heasgarnich, 27/414384, 1050 m, x 1989, Fryday (E, hb. Fryday). V.C. 92, South Aberdeen: Glas Maol, 37/1677, c. 900 m, on pebbles and boulders in north-facing corrie, 1991, Fryday 2933 (BM, hb. Fryday). V.C. 97, Westerness: Knoydart, Barrisdale, stob a’chearcaill, 18/8303, c. 650 m, shaded rock in gulley, 1990, Fryday 1171 (hb. Fryday); Fort William, Aonach Mór, 27/1972, 1150 m, 1990, Fryday 1214 (E); Creag Meagaidh, 27/4087, 1000 m, on low siliceous boulders in grass heath above area of late snow-lie, ix 1994, Fryday 5608–5610 & Gilbert (UPS, hb. Fryday); ibid., 1995, Fryday 6163 (hb. Fryday). V.C. 98, Argyll Main: Glen Coe, Coire nam Beitheach, 27/1454, c. 1100 m, vertical rocks in NE-facing coire influenced by late snow-lie, 1992, Fryday 3397 (hb. Fryday).—Wales: V.C. 49, Caernarvon: Snowdon range, Crib-goch, 23/6255, c. 850 m, pebbles in Festuca heath, 1993, Fryday 4671 (NMW, hb. Fryday). Prof. Dr H. Hertel and Dr G. Rambold are thanked for their detailed comments on the perplexing material of Stereocaulon plicatile, before its identity was revealed. The first author acknowledges the receipt of a Research Scholarship from the University of Sheffield and a grant from the British Ecological Society to cover the costs incurred during herbarium visits to BM and E.

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Our sincerest thanks go to Dr Oliver Gilbert for his inspiration in our studies of montane lichens and for his memorable companionship in the mountains, often in far from clement conditions! It is with the greatest pleasure that we dedicate this paper to him. R        Fryday, A. M. (1996) A provisional re-assessment of the non-yellow species of Rhizocarpon occurring in the British Isles. British Lichen Society Bulletin 78: 29–40. Jahns, H. M., Klöckner, P., Jørgensen, P. M. & Ott, S. (1995) Development of thallus and ascocarps in Stereocaulon tornensis. Bibliotheca Lichenologia 58: 181–190. Jørgensen, P. M. & Jahns, H. M. (1987) Muhria, a remarkable new lichen genus from Scandinavia. Notes from the Royal Botanic Garden Edinburgh 44: 581–599. Lamb, I. M. (1974) The lichen genus Argopsis Th. Fr. Journal of the Hattori Botanical Laboratory 38: 447–462. Purvis, O. W., Coppins, B. J., Hawksworth, D. L., James, P. W. & Moore, D. M. (1992) The Lichen Flora of Great Britain and Ireland. London: Natural History Museum Publications. Rodwell, J. S. (1992) British Plant Communities 3. Grassland and Montane Communities. Cambridge: Cambridge University Press. Accepted for publication 16 August 1996