Lichenologist 32(3): 207–224 (2000) doi:10.1006/lich.2000.0269 Available online at http://www.idealibrary.com on ON RHIZOCARPON OBSCURATUM (ACH.) MASSAL., WITH NOTES ON SOME RELATED SPECIES IN THE BRITISH ISLES Alan FRYDAY* Abstract: The specimens upon which Lecidea petraea var. obscurata Ach., the basionymofRhizocarponobscuratum(Ach.)Massal.,isbasedareshowntobemostly referabletothespeciescurrentlyknownasR.lavatum(Fr.)Hazslin.Rhizocarpon reductumTh.Fr.isresurrectedtoaccommodatespecimenswithsmallascospores previouslyreferredthere.TherelatedspeciesR.sublavatumisdescribedfromthe ScottishHighlandsanddescriptionsprovidedforR.anaperum(Vain.)Vain.andR. amphibium(Fr.)Th.Fr.ThesespeciesarecomparedwithR.reductum,R.lavatum and R. petraeum. Rhizocarpon rubescens Th. Fr. is shown to be a distinct species recordedfromEuropeandN.America. (cid:1)2000TheBritishLichenSociety Introduction Many authors have commented on the variation apparent in specimens referred to Rhizocarpon obscuratum (Ach.) Massal. (Feuerer 1978; Timdal & Holten-Hartwig 1988) or have recognized that more than one taxonomic entity may be involved (Purvis et al. 1992). In particular, both Timdal & Holten-Hartwig and Purvis et al. comment on the problems of separating some specimens from R. lavatum (Fr.) Hazslin. Conversely, Feuerer (1991), in his most recent treatment of the group, included in the synonymy of R. obscuratum many entities previously recognized as distinct species (e.g. R. anaperum, R. submodestum), a treatment that has not gained general approval(Timdal1992). Thomson(1967, 1997)alsohasawiderconceptof the species including R. lavatum and R. postumum within the synonymy. ExaminationofthespecimensuponwhichLecideapetraeavar.obscurataAch., thebasionymofR.obscuratum,isbasedrevealedthattheyaremostlyreferable tothespeciescurrentlyknownasR.lavatum.RhizocarponreductumTh.Fr.is resurrected for specimens with small ascospores and a thallus containing stictic acid formerly placed there, whereas specimens with larger ascospores and a thallus lacking lichen substances are mostly referred to R. lavatum. DetaileddescriptionsareprovidedforR.reductum,R.amphibium(Fr.)Th. Fr. and R. anaperum (Vain.) Vain. and these are compared to R. petraeum, R. lavatum and other similar species (i.e. R. postumum (Nyl.) Arnold, R. subpostumum (Nyl.) Arnold and R. rubescens Th. Fr.). A further species, *DepartmentofLandscape,UniversityofSheffield,Sheffield,S102TN,UK. PresentAddress:Herbarium,DepartmentofBotany&PlantPathology,166PlantBiology,Wilson Road,MichiganStateUniversity,EastLansing,MI48824,USA.E-mail:[email protected] 0024–2829/00/030207+18r35.00/0 (cid:1)2000TheBritishLichenSociety 208 THE LICHENOLOGIST Vol. 32 R. sublavatum Fryday sp. nov., with ascospore characters intermediate between R. reductum and R. lavatum, is recognized from the British Isles. Althoughthisentityismainlyconfinedtohighaltitudes,itmayhaveaddedto the confusion surrounding this complex. A comprehensive revision of the R. obscuratum complex in Norden is currently underway in Scandinavia (P. G. Ihlen pers. comm.) and, conse- quently,thiscontributionislimitedtoaconsiderationofthetaxathatoccurin the British Isles. Materials and Methods ObservationsarebasedonmaterialcollectedbytheauthorfromtheBritishIslesandspecimens heldinBM,E,&MSC.CriticalmaterialwasobtainedonloanfromH-ACHandUPS-ACH.All specimenscollectedbytheauthorareheldinhispersonalherbariumunlesscitedotherwise. Microscopic descriptions are based on observations made of hand-cut sections mounted in water and 10% KOH. All ascospore measurements were made in 10% KOH and exclude the perispore.Thedimensionsaregivenas(smallestmeasured)arithmeticmean-standarddeviation –arithmeticmean–arithmeticmean+standarddeviation(largestmeasured).Foreachspecies atleast15ascosporesweremeasuredfromatleastthreedifferentspecimensandinthecaseof R.sublavatum,35ascosporesweremeasuredfromfivedifferentspecimens.Onlytenascospores fromoneapotheciumweremeasuredfromtheH-ACHspecimenofLecideapetraeavar.obscurata. Thin-layerchromatography(TLC)followedthemethodsofWhite&James(1985). Typification of Rhizocarpon obscuratum The thallus of R. obscuratum is usually reported as lacking lichen substances (Foucard1990;Purvisetal.1992;Timdal&Holten-Hartwig1988;Thomson 1967, 1997; Wirth 1980) although Feuerer (1978, 1991), Timdal & Holten- Hartwig (1988) and Wirth (1995) mention that the thallus sometimes reacts K+yellow. Ascospore dimensions are usually reported as 20–32(cid:2)9–15(cid:1)m (Feuerer 1978; Purvis et al. 1992; Timdal & Holten-Hartwig 1988; Wirth 1995). However, examination of a large number of specimens (c. 50) from the British Isles by TLC and spot-tests with K and PD revealed that all con- tained stictic acid (one also contained norstictic acid) and had submuriform ascospores <25(cid:1)m long. Examination of herbarium material from Europe, N. America and the S. Hemisphere revealed a number of collections with longer (up to 30(cid:1)m), eumuriform ascospores, although there was a con- tinuum from these larger ascospores to those with more typical dimensions. Several specimens were discovered containing norstictic acid in addition to sticticacidbutonlyone(fromN.America)hadascospores <30(cid:1)mlongand lacked any lichen substances. InordertoresolvethisapparentdiscrepancythespecimenofLecideapetraea var. obscurata in the Acharius herbarium of the Natural History Museum, London (BM-ACH) was inspected. This was found to have a thallus lacking lichen substances, apothecia with a thick raised excipulum and eumuriform ascospores measuring 32·5–36·0(–50·0)(cid:2)12·0–15·0(cid:1)m, clearly placing it in the species currently known as R. lavatum. In addition, a specimen in Elabelled‘‘‘Switzerland,M.Schleicher’’.Herb.Menzies’andapparentlyalso partoftheoriginalcollection(‘HabitatinsaxismontiumHelvetiae.Schleicher’, 2000 Rhizocarpon obscuratum group—Fryday 209 Acharius 1810) was found to have ascospores measuring 34–43(cid:2)13–16(cid:1)m and a tumid excipulum; that is, also referable to R. lavatum. Examination of thematerialinUPS-ACHrevealedthat,thistoo,wasreferabletothespecies currently called R. lavatum although, from the substratum, it appeared to be from a different collection to that in BM-ACH and E. Sheet212inH-ACHislabelled‘Lecideapetraeavar.obscurataLich.Univ.’ in pencil and consists of four specimens numbered 681, 416, 429 & 415, all on different substrata and apparently representing four separate collections. A further specimen (495) is now missing. Professor P. M. Jørgensen (pers. comm.) has suggested that this specimen is probably that now housed in UPS-ACHas‘thatherbariumconsistsmainlyofspecimensremovedfromthe original Acharius herbarium by Agrelius, with permission from his father-in- law,Acharius’.Sheet212isannotatedinink‘var.obscurata’inthebottomleft hand corner (i.e. below specimen 429), ‘Lecidea lygaea’ in the bottom right (i.e. below specimen 415) and ‘Helvetica’ in the bottom centre (i.e. immedi- atelybelowthemissingspecimen).Therearealsoillegiblepencilannotations after ‘Lecidea lygaea’ in the bottom right and above ‘Helvetica’ in the centre. This later annotation would have been partly obscured by the missing specimen and appears to start with the letters ‘Sch ...’ and is possibly ‘Schleicher’. One specimen (415) is referable to Lecidella stigmatea (Ach.) Hertel & Leuckertandtwo(681&429)arereferabletothespeciescurrentlyknownas R.lavatum,ofwhichone(429)appearstobefromthesamecollectionasthat inBM-ACHandtheSchleichermaterialinE.Thefourthspecimen(416)has a thallus reacting K+yellow, PD+orange and ascospores measuring (19·3–) 19·38–22·28–25·18(–25·8)(cid:2)(8·0–)8·72–10·56–12·40(–14·5)(cid:1)m and with 8–11cellsvisibleinopticalsection.Thisspecimencoincideswiththeconcept of R. obscuratum from the British Isles detailed above. The confusion between R. obscuratum and R. lavatum thus dates back to the original description of Lecidea petraea var. obscurata but it appears clear that Acharius’s concept of this taxon coincides with what we now know as R. lavatum. As the thallus of R. lavatum lacks lichen substances this explains the widely held opinion that R. obscuratum does not contain stictic acid. If Acharius’s original concept is accepted then adherence to the rules of nomenclature would demand that the name R. obscuratum should be applied to the species currently known as R. lavatum and that a new name would be required for the entity with small ascospores currently included in R. obscuratum. However, as the re-naming of R. lavatum as R. obscuratum would causeconsiderableconfusionthiscourseofactionistobeavoidedifpossible. ExaminationofthecollectionsreferredtoR.obscuratuminBM,mostlyfrom theBritishIslesandNorthernEurope,revealedthatuntiltheearlyyearsofthe twentieth century L. petraea var. obscurata was used for both the large-spored entity lacking lichen substances and the small-spored entity with stictic acid. However,somespecimensofthelatterwerereferredtoL.petraeavar.cinerea Leight. (pale grey thallus), L. petraea var. fimbriata Leight. (reduced thallus with a well-developed, fimbriate prothallus), or L. petraea f. dispersa Leight. (dispersed areoles on a continuous, black prothallus). The name R. reductum Th. Fr. was then taken up for the small-spored entity, chiefly by W. Watson, 210 THE LICHENOLOGIST Vol. 32 and this continued to be used [later as R. obscuratum var. reductum (Th. Fr.) Eitner,e.g.Duncan(1970)]untilthelastquarterofthecenturywhenthevar. reductum was subsumed within R. obscuratum (e.g. Hawksworth et al. 1980), thusreturningtothesituationthatexistedacenturyago.Rhizocarponreductum was recently recognized as a distinct species by Foucard (1990), although he separateditfromR.obscuratumonmorphologicalcharacters.Theproblemof R. obscuratum was recognized by Imshaug, who referred his collections of the small-sporedentityfromtheFalklandIslandstoanewspecies(R.marginatum in sched.), and by Lamb who determined two collections from the Cape Breton Islands as R. plicatile. Although this species is usually considered to containnorsticticacid,Lambhadseentheisotype(BM)andknewthatitdid not (Fryday & Coppins 1996). The current concept of R. obscuratum is a combination of the small-spored entity with a thallus containing stictic acid and specimens with larger ascosporesandathalluslackingsticticacid,whicharereferabletoR.lavatum. Although it probably goes against Acharius’s intentions, it would be possible to typify the name on specimen no. 416 in H-ACH, thus fixing the name on the small-spored entity. However, given the current understanding of the species and its wide misapplication in the past, any attempt to save the name is likely to add to the confusion surrounding its use. Also, H-ACH 416 is in poor condition with very few apothecia containing mature ascospores and would not make a good lectotype. It seems that the wisest course of action will be to formally reject the basionymL.petraeavar.obscurataAch.thuspreservingthecurrentusageofR. lavatum.However,thiswillnotbedoneuntilafterthecomprehensiverevision ofthegroupcurrentlyunderwayinNorway(seeabove)iscomplete.Although specimens referred to R. lavatum are united by their large, eumuriform ascospores and epihymenium containing both aeruginose and dilute purple- brown pigment, they are variable in thallus and apothecia morphology and it is possible that significant differences exist between Lecidea petraea var. obscurata and R. lavatum, which will result in their remaining as separate entities. For the same reason it is not appropriate to select a lectotype from among the specimens in BM-ACH, H-ACH and UPS-ACH at this stage. The small-spored entity with a thallus containing stictic acid is, however, clearly distinct from the Acharius material of L. petraea var. obscurata (except forspecimen416)and,consequentlyR.reductumTh.Fr.isresurrectedforit. Unfortunately,thelectotypeselectedby Feuerer(1991) forR.reductum[Hb. Univ.Upsaliensis(L-75089)133008]isatypicalinhavingathallusthatdoes notcontainsticticacid,reflectingtheunderstandingofthespeciesatthattime. However,goodtypicalspecimensofR.reductum(asR.obscuratum)havebeen distributedinexsiccatae(e.g.HertelLecideaceaExsiccate:No.39–seebelow). The Species Rhizocarpon reductum Th. Fr. Lich. Scand. 2: 633 (1874); type: Sweden, Ska˚ne, Helsingborg par., Helsingborg, 1870, S.Almqvist.(UPS—lectotypeselectedbyFeuerer1991). 2000 Rhizocarpon obscuratum group—Fryday 211 Thallus effuse or in discrete patches 1–2cm diam., sometimes coalescing to cover larger areas, grey to brown, cracked-areolate, thin to moderately thick, very rarely almost subsquamulose; areoles 0·2–0·4mm diam., slightly convex or flat; prothallus usually present, particularly at margin, sometimes dominant, especially in shaded situations. Photobiont chlorococcoid, cells 8–10(–12)(cid:1)m diam. Apotheciablack,lecideine(cid:3)innatetosessile,flattoslightlyconvex,becom- ing more strongly convex when over mature, (0·2–)0·4–0·6(–0·8)mm diam.; properexcipleusuallywelldevelopedandslightlyraisedbutoftenexcludedin convexapothecia.Hymeniumhyaline,I+blue,120–140(cid:1)mtall;epihymenium olivaceous (K+blue, N+red), rarely brown. Paraphysoids slender, c. 1·0(cid:1)m thick, scarcely swelling at apex, without strongly delimited pigmented cap. Asci c. 65–80(cid:2)25–33(cid:1)m, slightly clavate, Rhizocarpon-type. Ascospores hyaline, halonate, submuriform, occasionally becoming muriform on matu- ration, (3–)5–8·36–10(–14) cells in optical section, 8 per ascus, (17·0–)18·3– 21·6–25·0(–30·0)(cid:2)(8·0–)9·5–10·8–12·0(–13·5)(cid:1)m, length/breadth ratio 1·75–2·1–2·86. Hypothecium mid- to dark-brown. Excipulum of radiating hyphae, outer cells blue-black, K+yellow solution. Conidiomata not seen. Chemistry. Usually C(cid:4), K+yellow, PD+orange. Stictic acid detected by TLC. Rarely K(cid:4), PD(cid:4)(no substances) or K+red, PD+orange (stictic and norstictic acids) Notes. Rhizocarpon reductum is a common, widespread species of siliceous rocks, occurring from near sea-level to the tops of the highest mountains in England and Wales (Fryday 1996a), although very rare at high altitudes in Scotland. It usually occurs on exposed surfaces when the thallus is thick and forms a continuous crust, occasionally appearing almost subsquamulose. However, it also occurs as a number of ecotypes, which were described as infraspecific taxa (of Lecidea petraea) by Leighton (1879). When growing on hard,fine-grainedrock(especiallypebbles)thethallusisusuallysmall(<1cm diam.) and often surrounded by a black, fimbriate prothallus (var. fimbriata); on shaded, usually vertical surfaces, it occurs as(cid:3)flat areoles, widely dis- persedonablackprothallus(f.dispersa).Italsooccurswithapalegreythallus (var.cinerea)that,withtheoftenconcentricallyarrangedapothecia,hasledto confusion with R. petraeum. In all its forms R. reductum can be distinguished by the combination of stictic acid and small, submuriform (to muriform) ascospores (Fig. 1C). Many British specimens with large (>30(cid:1)m long), eumuriformascosporespreviouslyreferredtoR.reductumarebetterplacedin either R. petraeum (Wulfen) A. Massal. [syn. R. concentricum (Davies) Beltr.] or R. lavatum. Some collections from the Southern Hemisphere (e.g. Imshaug 41135, 41475, 58175), have slightly larger, more muriform ascospores [25–27(–30)(cid:2)11–12(cid:1)m] but as they agree with R. reductum in all other respects, and other Southern Hemisphere collections (e.g. Imshaug 41495, Streimann 55266) have ascospores typical of R. reductum, they are included within the taxon. 212 THE LICHENOLOGIST Vol. 32 F. 1. Ascospores in the Rhizocarpon obscuratum group. A, R. sublavatum; B, R. anaperum; C,R.reductum;D,R.lavatum.Scale =10(cid:1)m. 2000 Rhizocarpon obscuratum group—Fryday 213 Rhizocarpon reductum appears to be a colonizing species, occurring early in the succession on newly exposed, siliceous rocks. Associated species include many other species known to be colonizing species of this substratum, for exampleLecidealithophila,Porpidiacinereoatra,P.crustulata,P.tuberculosaand Trapelia coarctata. Newly exposed siliceous rock is a highly stressed environ- ment and Rodgers (1990), using the triangular ordination method of Grime (1977), found that R. reductum (as R. obscuratum) occurred closest to the stress-tolerant pole of any of the 34 species studied. One specimen of R. reductum(hb.Simkin)wascollectedfromtheflueofthesmeltmillatadisused lead mine. The stone appears to be from the inside of the flue, now dismantled, located very close to the source of fumes in the smeltmill and before much of the contamination was extracted, so is likely to be heavily contaminated. When Feuerer (1991:131) chose a lectotype for R. reductum, he selected an atypical specimen lacking stictic acid, reflecting the traditional concept of the chemistry of R. obscuratum, of which he considered it a synonym. The occasionalspecimencontainingnorsticticacid(inadditiontosticticacid)has usually been identified as R. plicatile but the type specimen of that species has been shown to be referable to Stereocaulon (Fryday & Coppins 1996). Exsiccatespecimensexamined(asRhizocarponobscuratum):- Lecideacea exsiccatae (Hertel) No. 39. Dänemark, N-Jütland, Gemeinde Hansthom; an der StrassezwischerVeslösundTömmerby,37(cid:5)03(cid:6)N,9(cid:5)00(cid:6)E,PioniervegetationonSchotterstreifen eines ehemaligen Buhnkörpes, 15m, an losen Steinen (zumeist Feuerstein-Knollen), ix 1978, H.Hertel&Ch.Leuckert.(E,BM). LichensDaniciExsiccati:90.Hab.Onpebblesofoldbeach-ridge.Alt.5–10m.Læsø:between BaustenBakkeandLergrausBakke.UTM:32VP254547,5vii1996,SteenN.Christensen(BM). LichenesGalliciExsiccati(Claudel&Harmand,1903):194.Harm.Catal.Lich.Lorr.p416– supràsaxaareneria,Vosges,T.Harmand(BM). Lichenotheca Polonica fasc. 2, (F. Krawiec, 1935) 58. Lubosz pow. Miedzychód. Na glazach narzutowych skupionych nad droga – Ad lapides ad viam compositos, 24 ix 1934, F. Krawiec (E,BM). Selected specimens examined. Ireland: V.C. H1, South Kerry: Connar’s Pass, Lough Doon, Dingle Peninsula, 01/5006, 500m, small sandstone boulder, 1994, Fryday [5181] & O. L. Gilbert;MountBrandon,DinglePeninsula,01/4711,500m,dryverticalsandstonecrag,1994, Fryday[5248]&O.L.Gilbert.—U.K.:England:V.C.1,W.Cornwall:IslesofScilly,StMartins, TurfyHill,onexposedrocksatHWMs.t.,11iv1968,P.W.James(BM).V.C.5,S.Somerset: Corfe,W.Watson(BM);Taunton,onwalltowardsUpperCheddon,ii1939,W.Watson.V.C.6, N. Somerset: Mendip Hills, Ubley Warren, 31/5056, 250m, vitrified spoil from disused lead mine, 1994, Fryday 5178, 5179. V.C. 11, S. Hampshire: Lyndhurst Moor, 1906, Reed (BM). V.C.15,E.Kent:Dungeness,1955,J.R.Laundon1299(BM).V.C.24,Buckinghamshire:near Wendover,ix1908,H.P.Pender(BM).V.C.28,W.Norfolk:ThetfordWarren,onflints(BM). V.C. 40, Salop: Caer Caradoc, W.A. Leighton (BM). V.C. 62, NE. Yorkshire: Cleveland, Lonsdale,W.Mudd(BM);Goathland,WheeldaleGill,44/797991,150m,acidrocksbystream, vii1985,Fryday(hb.Fryday).V.C.69,Westmorland:Helvellyn,35/3415,750m,acidrock,ix 1988,Fryday(hb.Fryday).V.C.70,Cumberland:Penrith,Alston,Gilgarronon,onhardrocks, W.A.Leighton(BM);ibid.?CoalcakeQuarry(?Coalcleugh,35/80–45(cid:4),550m),stones,5viii 1881, J.A. Martindale (BM); Alston, Nenthead Mines, 35/784432, 460m, flue of smeltmill at disused lead mine, 19 x 1998, J. Simkin (hb. Simkin). Wales: V.C. 46, Cardiganshire (Ceridigion): Elarch, Llawr-y-cwm-bach mine, 22/708854, 230m, block spoil of disused lead mine,1994,Fryday[5041,5042]&S.Chambers;Devil’sBridge,MynachValeMine,22/772755, 270m,blockspoilofdisusedleadmine,1994,Fryday[5022,5023]&S.Chambers.V.C.47, Montgomeryshire: Dylife, 22/862934, 375m, block spoil of disused lead mine, 1994, Fryday [5072,5076–5078]&S.Chambers.V.C.49,Caernarvonshire:CwmIdwal,TwllDu,23/6558, 214 THE LICHENOLOGIST Vol. 32 525m, side of large boulder, 1994, Fryday 5321; Pass of Llanberis, Cwm Uchaf, 23/620551, 825m,verticalrockface,1995,Fryday6347.Scotland:V.C.88,Mid-Perthshire:Killin,Alltna Ceardaich,27/5734,225m,acidboulder,1991,Fryday2030,2033.V.C.92,S.Aberdeenshire: Glen Clunie, Creag nan Gabhar, 37/1484, 500m, vertical, quartzite rock-face, 1992, Fryday 3470.V.C.97,W.Inverness-shire:Sunart,Strontianriver,17/8666,250m,verticalacidrock faceinravine,1992,Fryday[3175],J.Poelt,B.J.Coppins&P.W.James.V.C.100,ClydeIslands: Arran,Kilmarie16/955207,10m,dryshingleaboveMHWnst,7vii1958,G.A.M.Scott(BM). V.C.105,W.Ross-shire:Knockan,eastsideofCulMór,29/1611,700m,Torridoniansandstone crags,1991,Fryday2810;Balmacara,LochPalascaig,18/7829,150m,verticalacidrock-face, 1992,Fryday3364;Kintail,FallsofGlomach,28/016260,225m,verticalacidrock-face,1993, Fryday 4507. V.C. 110, Outer Hebrides: South Harris, Roineabhal, Cleat Thurro, 18/0385, 150m, siliceous rock face, 1991, Fryday 2569 (with norstictic acid).—Sweden: Hälsingland, Bollnäs. Arlderomshemmet, 20 vi 1950, G. Kjellmert (MICH).—Switzerland: Habitat in saxis montiumHelvetiae,1810,M.Schleicher(E–Hb.Menzies).—USA:Michigan:IsleRoyal,Rock harbour, 1930, Povah, Brown, McFarlin & Lowe 486 (lacking lichen substances) (MICH). Minnesota:StLouisCounty,Babbit,DunkaRivernearEriemine,Sec.4,T60N,R12W.inred pine stand, middle age, 1977, C. Wetmore 27881 (with norstictic acid)(MICH). Washington: Skagit County, Shannon Point, Fidalgo Island, 48(cid:5)30(cid:6)N, 122(cid:5)41(cid:6)W, 20m, on granite, open areanearseashore,11viii1978,B.Ryan(MICH.).—Canada:Newfoundland:CornerBrook, BayofIslands,iii1896,A.G.Waghorne(withnorsticticacid)(BM).NovaScotia:CapeBreton Island,InvernessCounty,vicinityofMargareeForks,65m,onstonesonearthbankatroadside, 1952,I.M.Lamb6734(MICH).—Australia:Victoria:PohlnerRoad,GrampiansNationalPark, 35km SW of Ararat, 36(cid:5)59(cid:6)S 142(cid:5)25(cid:6)E, 300m, dry sclerophyll forest on moderate slope, on exposed small rocks, 1994, H. Streimann 55266 (MSC).—New Zealand: South Island: Canterbury, banks Peninsula, border of Mt Herbert and Wairewa Counties, 1000m, tussock grass at summit of Herbert Peak, 1973, H.A. Imshaug 58175 (MSC).—Falkland Islands: E. Falkland: Stanley, UTM Grid 21F VC 2971, 200m, outcrops along Goat Ridge, 1968, H.A. Imshaug [41495] & R.C. Harris (MSC); Mullet Creek, Stanley, UTM Grid 21F VC 3270, 35–50m,streambelowfiord,1968,H.A.Imshaug[41475]&R.C.Harris(MSC).W.Falkland: MtAdam,.UTMGrid21FTC8782,610m.,shelteredcliffsonridgeWofnorthernlake,1968, H.A.Imshaug[41135]&R.C.Harris(MSC). Rhizocarpon sublavatum Fryday sp. nov. Thallus rimoso-areolatus, tenuis, medi- ad atrocinereus, 0·2–0·3(–0·4)mm diametro. Apothecia sessilia 0·3–0·5(–0·8)mm diametro, epihymenium olivaceo-caeruleum. Ascosporae eumuriformes,cellulis11–41insectioneopticali,17·0–38·0(cid:2)11·0–25·0(cid:1)m.Thallussinesub- stantilislichenalibus.Rhizocarponanaperumthallobrunneoareolatopigmentisqueapothecialibus internisnonnisibrunneiscinereisquediffert. Typus:Caledonia,V.C.97,Westerness,BenNevis,CoireLeis,27/171712,1050m,onloose stones below crag, 5 September 1996, A.M. Fryday 7101 (E—holotypus; B, BM, UPS, M, MSC—isotypi). Thallus effuse, usually in small patches 1–2cm diam. but sometimes coalescing to cover larger areas, cracked-areolate, thin, mid- to dark grey occasionally brown-grey; areoles 0·2–0·3(–0·4)mm diam., flat to slightly convex, hypothallus clearly visible. Photobiont chlorococcoid, cells (10–)12– 15(–18)(cid:1)m diam. Apothecia black, lecideine, innate when young, becoming sessile when mature, when sessile 0·3–0·5(–0·8)mm diam.; proper exciple persistent, thin and raised. Hymenium hyaline, I+blue, 120–140(cid:1)m tall; epihymenium olivaceous-blue (K+blue, N+red). Paraphysoids c. 2·0(cid:1)m thick, scarcely swellingatapex(upto3·0(cid:1)m),withpigmentedcap,sparinglybranchedand anastomosing.Ascic.80–100(cid:2)(27–)32–40(–45)(cid:1)m,Rhizocarpon-type.Asco- spores hyaline occasionally blue-black when mature, halonate, eumuriform, 2000 Rhizocarpon obscuratum group—Fryday 215 11–23·74–41 cells in optical section, 8 per ascus, 17·0–30·9–38·0(cid:2)11–16·8– 25·0(cid:1)m, length/breadth ratio 1·5–1·85–2·6. Hypothecium mid- to dark- brown. Excipulum of radiating hyphae, pale brown with darker outer cells (K+blue-black). Conidiomata not seen. Chemistry. C(cid:4), K(cid:4), KC(cid:4), PD(cid:4). No substances detected by TLC. Notes. Rhizocarpon sublavatum is, in many respects, intermediate between R. reductum and R. lavatum and has probably contributed to the confusion surrounding these species. Like R. lavatum, with which it often grows, it has eumuriform ascospores but they are both shorter (33·0–50·0(cid:1)m long in R. lavatum) and have a lower length/breadth ratio (2·0–3·1 in R. lavatum) (Fig. 1A&D).Italsohassmaller,moresessileapothecia.ThethallusofR.lavatum is also more often rimose than areolate and browner than in R. sublavatum. It is also often the host to parasitic fungi (Endococcus species) but these have notbeenobservedonR.sublavatum,evenwhenthetwospeciesgrowtogether. Rhizocarpon reductum has smaller, submuriform spores (Fig. 1C), a thallus containing stictic acid (K+yellow, PD+orange) and is rarely encountered at the high altitudes at which R. sublavatum occurs. The species closest to R. sublavatum in both macroscopic and microscopic characters is R. anaperum; both have spores of a similar size and shape (Fig. 1A & B) but R. anaperum has a taller hymenium with narrower, more branched paraphysoids as well as a different apothecial pigmentation – only brown and grey pigments being present. Macroscopically, R. anaperum has a browner, more granular- areolate thallus. The two species often grow together when they remain morphologically distinct. The species recorded from a series of quadrats on Aonach Mór, including R. sublavatum, are listed in Table 1. Rhizocarpon sublavatum is typically a species of damp, siliceous, montane rocks. It is widely distributed across the Scottish Highlands (Fig. 2) at altitudes of (400–)700–1340m although, like several other species, it tends to be restricted to damp habitats (e.g. north- facing coires, areas of prolonged snow-lie) in the eastern Highlands but becomes more widely distributed in the damper, western Highlands (Fryday 1997). This distribution suggests that R. sublavatum is a northern montane species, perhaps with some oceanic affinities. Although, at present, recorded onlyfromScotlanditalmostcertainlyalsooccursinScandinaviaandprobably elsewhere in boreal-arctic regions. Rhizocarpon sublavatum often forms mosaics with species such as Ionaspis odora, Porpidia contraponenda, P. tuberculosa, R. anaperum, R. lavatum and Stereocaulon tornense, although at its typelocality,whereitisabundant,itisalmosttheonlylichengrowingonloose stones at the base of a high cliff, suggesting that it is a colonizing species, perhaps replacing R. reductum in this role at high altitudes. Additional specimens examined: U.K.: Scotland: V.C.88, Mid-Perthshire: Ben Lawers NNR, LochannanCat,27/6442,750m,rocksnearstream,6vii1989,Fryday;MeallnaCnap-laraich, 27/5039,775m,siliceousrocks,vii1989,Fryday;BeinnHeasgarnich,AlltTarsuinn,27/4338, 700m,topofacidrockbesidestream,1991,Fryday(2227);MeallCorranaich,27/6140,1000m, quartzitepebble,1991,Fryday2158a.V.C.96,Easterness:Cairngorm,CisteMhearad,38/0104, 216 THE LICHENOLOGIST Vol. 32 T 1. Species recorded from 2(cid:2)2m quadrats above snow-bed on Aonach Mór (GR 27/19·72. Alt.1100m) Distancefromupperedgeofsnow-bed(m) 0 2 4 6 8 Cover(%) Vascularplants 5 10 50 75 60 Bryophytes 80 75 30 15 30 Lichens 5 10 15 5 7 Rocks 10 15 20 10 10 Averagesizeofrocks(cm) 5–10 5–10 10 10–20 5–10 VascularPlants Deschampsiacaespitosa 2 3 6 8 8 Gnaphaliumsupinum 1 1 3 2 1 Saxifragastellaris . 1 3 1 . Huperziaselago . . 1 1 . Carexbigelowii . . 2 4 4 Deschampsiaflexuosa . . . . 1 Bryophytes Polytrichumsexangulare 8 7 6 5 4 Marsupellaspecies 5 2 2 . . Gymnomitrionspecies 4 3 2 3 4 Moerckiablyttii 1 3 1 . . Racomitriumheterostichum 2 2 3 2 . Polytrichumalpinum . 1 3 1 3 Racomitriumlanuginosum . . 1 1 3 Dicranumspecies. . . 1 1 3 ‘Brightgreenliverwort’ . . . . 3 Lichens Stereocaulontornense 4 4 4 4 4 Ionaspisodora 1 2 1 2 . *Rhizocarponhochstetteri ‘subsp.rufoatrum’adint. 2 2 1 2 2 Porpidiacontraponenda 3 4 1 2 2 Micareaparatropa(syn.M.subviolascens) 1 2 2 3 3 Verrucariamargacea 2 3 1 1 . Porpidiacrustulata 4 4 3 . 3 Micareamarginata 1 1 . . . Porpidiamacrocarpa 2 . 2 . 2 Stereocaulonsaxatile 1 . . 1 . Rhizocarponspecies 1 . . . 1 Trapeliaplacodioides 1 . . . . *Rhizocarponhochstetteri . 2 2 2 . Rhizocarponlavatum . 2 . 1 1 Agonimiatristicula . 1 . . . Cladoniasubcervicornis . 1 . . . Micareaturfosa . 1 1 1 3 Cladoniabellidiflora . . 1 1 . Trapeliaobtegens . . 1 1 . Stereocaulonvesuvianum . . 1 1 . Leprarianeglecta . . 1 1 . Polyblastiahelvetica . . 1 . 1 Lecidealithophila . . . 1 1 Porpidiatuberculosa . . . 1 . Frutidellacaesioatra(syn.Lecideacaesioatra) . . . 1 . Rhizocarponsublavatum . . . 1 . Cecidoniaxenophana . . . . 1 Polyblastiagothica . . . . 1 Catillariacontristans . . . . 1 Baeomycesrufus . . . . 1 *=RhizocarponcolludenssensuFryday(1996b).