Introduction
The genus Lecanora (Lecanorales, Ascomycota) was described by Acharius (in Luyken Reference Luyken1809: 90) and is one of the largest genera of crustose lichens, with about 300 species. It is easily recognized by the superficial apothecia with thalline margins, bearing Lecanora-type asci containing colourless simple spores of small to moderate size. Many of the species have been little studied, and, for those which have received attention, there are often problems with their variation and delimitation. This paper deals with the the authorship of L. albescens, the taxonomy of Lecanora conferta, and the nomenclature of L. muralis. An exclamation mark (!) indicates that the cited specimen has been critically studied.
The species
Lecanora albescens (Hoffm.) Branth & Rostr
Bot. Tidsskr. 3: 196 (1869).—Psora albescens Hoffm., Fl. Germaniae 2: 165 (1796); type: Germany, Bayern, München, Thalkirchen, on churchyard wall, December 1891, Arnold, Lich. Monac. Exs. 212 (H— neotype, not seen, selected by Śliwa Reference Śliwa2006: 295).
Parmelia galactina Ach., Meth. Lich. 190 (1803), nom. superfluous (Art. 52.1).
This lichen is related to Lecanora dispersa (Pers.) Sommerf. and is recognized by its whitish superficial thallus with small lobes at the margin. For detailed accounts see Śliwa (Reference Śliwa2006, Reference Śliwa2007). It is common on hard limestone rocks and walls where there is good illumination and nutrient enrichment.
Śliwa (Reference Śliwa2006) claimed that Flörke is the author of Lecanora albescens, giving the name as L. albescens (Hoffm.) Flörke in Flotow. Unfortunately, this is wrong because Flotow (Reference Flotow1828: 633) actually used Flörke's name as “Lecanora albescens Flk. in Litt. … ist synonym mit Lecanora Flotoviana Spr.” so that it was cited as a synonym and was therefore not validly published under Article 34.1 of the Code. Nowhere did Flotow publish Flörke's text, as Śliwa (Reference Śliwa2006) claimed. Therefore the correct authors remain as Branth and Rostrup, as given above.
Lecanora antiqua J. R. Laundon, sp. nov
MycoBank No. 518586
Differt a L. dispersa (Pers.) Sommerf. apotheciis pruinosis et solutione hypochloritis calcici aurantiacum reagenti. Thallus acidum 2,7-dichloro-6-O-methylnorlichexanthone et 2,7-dichloronorlichexanthone continens.
Typus: Great Britain, England, V. C. 55, Leicestershire: Twycross church, grid SK 339 049, north wall, on limestone blocks and lime mortar, 19 January 2004, Ivan Pedley 2004/10 (BM—holotypus! [TLC & HPLC: 2,7-dichloro-6-O-methylnorlichexanthone (major), 2,7-dichloronorlichexanthone (major), 2-chloro-6-O-methylnorlichexanthone (minor), norlichexanthone (trace), 2-chloronorlichexanthone (trace), 7-chloronorlichexanthone (trace)].
Lecanora conferta auct. angl., non (Duby) Grognot
(Fig. 1)
Thallus of white to dingy yellowish grey (= isabelline) granules, 0·1–0·5 mm, forming a distinct thick and warty crust in places, but elsewhere scattered, or on an inconspicuous thin crust, or immersed and therefore apparently absent. Prothallus not apparent. Photobiont belongs to the Chlorophyta, the cells coccoid, ± spherical, up to 20 µm diam.
A & B, Lecanora antiqua (holotype). Scales = 1 mm.
Apothecia 0·3–0·9 mm diam., scattered to crowded, mostly orbicular and plane, but becoming slightly convex and distorted when old, sessile. Thalline margins of apothecia c. 0·1 mm thick, white to dingy yellowish grey, pruinose, entire or notched, sometimes excluded when old. Disc usually plane but sometimes convex when old, light brownish grey to flesh-coloured, usually pruinose but sometimes naked. Amphithecium with abundant algae and a few crystals. Hypothecium colourless. Hymenium colourless, 50–70 µm high. Epihymenium narrow, 10–13 µm thick, with abundant granular crystals (insoluble in K, soluble in 50% nitric acid) to give it a brownish yellow colour. Paraphyses compact, thin, 1–2 µm thick, sparsely branched, broadening towards the tips, the apices colourless, not swollen. Asci clavate, narrow, 35–48 × 10–13 µm, eight-spored. Ascospores ellipsoid, simple, colourless, 11–13 × 5–6 µm.
Conidiomata not observed.
Chemistry. Thallus, apothecia margin, and disc C + bright orange-red, C + yellow, or occasionally C−, K + faint yellow or K−, P−. The positive reaction with bleach is due to the high concentration of xanthones whilst the occasional negative reaction indicates a low concentration. For substances see under typus above.
Etymology. Antiqua: ancient, referring to the habitat.
Taxonomy. This lichen has been called Lecanora conferta (Duby) Grognot in the past, despite bearing no resemblance to this species. The combination L. conferta was made by Grognot (Reference Grognot1863: 61), based on Patellaria conferta Duby (Reference Duby1830: 654), described from Normandie in France “Ad muros argillaceos Neustriæ propè Bernay (cl. Le Prév.)” (Duby Reference Duby1830). Bernay is in the Eure department. The holotype is in UPS! and is labelled “Parmelia conferta. L.E. p. 155.! In muris argillaceus Galliae occid. Prevost.”
In BM! there is a topotype in Malbranche, Lich. Normandie fasc. 5 no. 234 (1873). Both specimens are identical and agree with Duby's description. The species has crowded, large, swollen convex apothecia, 0·5–1·5 mm diameter, with brown discs and excluded margins, which are C− and KC−. It does not belong to the Lecanora dispersa group, but instead resembles L. symmicta. The specimens are on soft rock, perhaps on a mud wall. Further work is required to establish if L. conferta is a distinct species.
Lecanora antiqua is identified by the colour test with bleach, which is most pronounced and often striking on the disc of the apothecia. However, some thalli are C−, apparently due to low concentrations of the xanthones in some specimens. It closely resembles L. dispersa, and there is some overlap of characters. However, field studies show that they are distinct. Lecanora antiqua usually has pruinose discs, and the thallus occasionally forms a well-developed crust which then resembles L. albescens. In L. dispersa the apothecia are usually naked, C−, and the thallus is either immersed or thin. Moreover, L. dispersa occurs on “a wide range of substrata” (Śliwa Reference Śliwa2007), in contrast to the restricted and specialized habitat of the new species. Lecanora antiqua is illustrated from the church at Llanrhaeadr-ym-Mochnant in Powys in Dobson (Reference Dobson2005: 218), as L. conferta.
Lecanora andrewii B. de Lesd. differs from L. antiqua in the possession of peltate apothecia with prominent whitish margins surrounding naked, non-pruinose, brownish, plane discs. Like L. antiqua it is C+, but it is also P+ orange. Lecanora fugiens Nyl. differs in having a brownish yellow thallus and apothecium margins. Both look quite different from L. antiqua, and have a positive P reaction, containing arthothelin and often pannarin. Both inhabit acid rocks, especially at the coast. The separation of the compounds of L. antiqua from other xanthones was illustrated in Figs. 11 and 12 of Orange et al. (Reference Orange, James and White2010) (as ‘conferta-unknowns’).
First record. This lichen was first recorded in 1992 from old plaster on church walls at Thursley in Surrey and Graffham, Greatham, Rustington, and West Thorney in West Sussex by Francis Rose, reported in Brightman (Reference Brightman1992), as Lecanora conferta. The original specimen from Britain, cited by Smith (Reference Smith1918: 280) from “near Aberdeen” (BM!) is neither L. antiqua nor L. conferta and remains unidentified.
Distribution. Common across the Midlands, extending into Lincolnshire and Yorkshire (Fig. 2). Scattered in other parts of the British Isles. No material has been seen from abroad.
The recorded distribution of Lecanora antiqua.
Ecology. Lecanora antiqua is remarkable in being largely confined to the vertical walls of medieval buildings, especially churches. For example, in Warwickshire off Watling Street, it is locally abundant on the vertical north, south, and west heavily restored 13th century walls of Caldecote church, abundant on the 13th century vertical east wall of the chancel of Grendon church, and locally abundant on the angled chamfered plinth (weathering) on the 14th century north wall of the chancel at Mancetter. In West Sussex it occurs on old plaster on the walls of several churches (Brightman Reference Brightman1992).
On medieval walls the new species is apparently confined to the interface between acid and calcareous surfaces. Thus on Caldecote church it grows on mortar subject to acid run-off from adjoining sandstone, on an old cement coating over sandstone blocks, and on sandstone itself subject to a calcareous run-off. On Northamptonshire churches it occurs mainly on vertical ironstone, which contains a high proportion of iron oxide, where there is run-off from nearby mortar. This contrasts with the related Lecanora crenulata Hook., which is also typical of medieval vertical church walls, but only on those of hard limestone where there is no acid run-off.
Additional specimens examined. Channel Islands: Sark: Vieux Port, WV 458 760, on east-facing gneiss wall of old stone shed, 1 viii 1999, P. W. James (BM!).—Great Britain: Wales: V.C. 35, Monmouth: Blaenau Gwent, St Andrew Tredunnoc, on church, ix 2009, M. Powell (hb. Powell!). V.C. 42, Brecon: Llanddew church, SO 055 307, on old red sandstone, 1998, I. Pedley 1998/52 & P. W. James (BM!); Merthyr Cynog church, SN 984 375, on lime mortar, 1998, I. Pedley 1998/56 & P. W. James (BM!).
Lecanora saxicola (Pollich) Ach
Lich. Univ. 431 (1810).—Lichen saxicola Pollich, Historia Plantarum 3: 225 (1777); type: Germany, “Circa Lauteren supra lapides, saxa ac muros ubique”, “HERBARIUM and TYPES: Unknown” (Stafleu & Cowan Reference Stafleu and Cowan1983: 330). Bayern: Fichtelgebirge, H. C. Funck, Cryptog. Gewächse des Fichtelgebirg's fascicle 34 No. 701, as Lecanora saxicola Ach. (1829) (BM, neotype!, selected here).
Lichen muralis auct.; Lecanora muralis Rabenh., Deutschl. Krypt-Flora 2 (1): 42 (1845).
Lichen versicolor Pers., in Usteri, Ann. Bot. 7: 24 (1794).
A Lecanora readily distinguished by its greyish green appressed lobes, often with whitish pruinose margins. It is common on damp horizontal surfaces, especially on paths of asphalt and concrete in urban areas, and on asbestos cement roofs before the ban on the use of this harmful building material. In natural habitats it is mostly confined to the tops of acid rock outcrops and boulders frequented by birds. Nitrophilous, photophilous, and xerophobous. The species is often compared to unsightly discarded chewing gum, also abundant on urban pavements, giving rise to the name “chewing- gum lichen” (Smith et al. Reference Smith, Aptroot, Coppins, Fletcher, Gilbert, James and Wolseley2009: 491). “Pavement rosette” is suggested here as a much nicer name for this attractive organism.
Lichen muralis Schreb., Spicil. Fl. Lips. 130 (1771) is a superfluous name for L. pallescens L., Sp. Plant. 2: 1142 (1753) [now Ochrolechia pallescens (L.) A. Massal.], which Schreber cited as a synonym. Therefore the current name of this lichen, Lecanora muralis, is wrong and the name L. saxicola is correct. The contest between the two names L. muralis and L. saxicola has a long history, going back at least to the early 19th century (Smith & Sowerby Reference Smith and Sowerby1807: 1695), and when Rabenhorst made the combination Lecanora muralis he even published it as “L. (saxicola) muralis”. Zahlbruckner (Reference Zahlbruckner1928: 632–644) listed some 97 uses of the name L. muralis in comparison with some 264 uses of L. saxicola. Thus historically the name L. saxicola has been used more often for the species; it means the Lecanora rock dweller and is easily remembered. Therefore it is perhaps unnecessary to introduce formal proposals to retain the current name L. muralis, but it is likely that a proposal will eventually be published to conserve it under Article 14 of the Code.
Lecanora saxicola looks quite different from most other species of Lecanora, which are crustose as opposed to placodioid. This lead Choisy to describe a new genus called Protoparmeliopsis M. Choisy (Reference Choisy1929: 524), based on only one lichen Lecanora muralis, but he made no new combination for the species. The genus Protoparmeliopsis was recognized by Hafellner & Türk (Reference Hafellner and Türk2001: 114) in their checklist of Austrian lichens, where three varieties of the unpublished “P. muralis” were listed.
I thank the staff of the library at the Royal Botanic Gardens at Kew for the use of their extensive literature and especially Dick Brummitt, who is the doyen of nomenclature, for examining the names in the works on Lecanora albescens, L. muralis, and Protoparmeliopsis, and for agreeing with my conclusions. The Natural History Museum (BM) kindly allowed me to examine their specimens. Ivan Pedley is thanked for sending me material and data, and Jack Elix is thanked for studying the chemistry of Lecanora antiqua. Lucyna Śliwa sent me reprints and studied the Twycross specimen but came to a different conclusion. The British Lichen Society's Mapping Recorder Mark Seaward supplied Fig. 2, Norman Robson corrected my Latin, and Frank Dobson informed me of the locality of his fine photograph. Two anonymous referees are thanked for their information and suggested amendments which have improved the paper. Alan Orange kindly photographed the type specimen of L. antiqua.
