STUDIES ON SOME SPECIES OF ARTHOTHELIUM OCCURRING IN THE WESTERN MEDITERRANEAN

Transcription

1 Lichenologist 28(1): (1996) STUDIES ON SOME SPECIES OF ARTHOTHELIUM OCCURRING IN THE WESTERN MEDITERRANEAN Martin GRUBE* and Mireia GIRALT Abstract: We present a survey of the six known species of Arthothelium occurring in the western Mediterranean. The oceanic A. lirellans, which may occur in the study area, is included for comparison; A. taediosoides is described as new and a key to all species is given. Arthothelium as understood today is composed of more-or-less distinct natural groups of species, some of them being compared here. Representatives of the A. sardoum group are related to species of the Arthonia radiata or A. galactites group on the basis of anatomical characters of the ascomata The British Lichen Society Introduction Lichenological work is flourishing in southern Europe, and many floristic studies have contributed to the knowledge of lichens, especially in Italy and Spain. More than 2100 infrageneric taxa are known from Italy, which to date is the best investigated country in the Mediterranean (Nimis 1993). In other Mediterranean areas, a comparable lichenological revolution may soon follow. However, the compilation of any lichen flora is considerably complicated due to taxonomic problems, particularly concerning crustose lichens. One difficult taxonomic group is represented by the species commonly placed in the Arthoniaceae. Currently, the delimitation of genera and the placement of species in this family is, for practical reasons, still based on ascospore septation patterns (muriform versus transversely septate only). This arrangement dates back to the last century when Massalongo (1852) was the first to segregate the Arthonia species with muriform ascospores to establish the genus Arthothelium. Keys to the European Arthothelium species have been provided by Poelt (1969) and Clauzade & Roux (1985). The contributions of Coppins & James (1979), Coppins & Tønsberg (1984) and Coppins (1992) have improved the understanding of species in Arthothelium, at least in Northern Europe. The genus Arthothelium has largely been overlooked in the Mediterranean. There are only a few old collections in herbaria, although some species seem to be quite common throughout the region. In a contribution focusing on species from Algeria and Tunisia it was pointed out that careful observation is sometimes necessary to find muriform ascospores and, therefore, to classify certain species as Arthothelium (e.g., A. crozalsianum; Faurel et al. 1955). Recently, there has been some discussion over the circumscription of the genus as well as over its ordinal placement. For example, James (1965) *Institut für Botanik, Karl-Franzens-Universität Graz, Holteigasse 6, A 8010 Graz, Austria. Department de Biologia Vegetal (Botànica), Facultat de Biologia, Universitat de Barcelona, Diagonal 645, E Barcelona, Spain /96/ $12.00/ The British Lichen Society

2 16 THE LICHENOLOGIST Vol. 28 combined Arthonia ilicina with non-muriform spores into Arthothelium, which has not been followed by Coppins (1992). Tehler (1990) even rejected the placement of Arthothelium in the same order as Arthonia, whereas Harris (1990: 41) suggested merging both genera. This study does not present a new generic concept, which would require a world-wide comparative treatment. Rather, we have focused on comparing the species traditionally included in Arthothelium that are known from the Mediterranean. Methods All measurements (in μm) of anatomical characters were taken from aqueous preparations. Ascospore ornamentation was observed with 1000 magnification. Lugol s solution (I) was used in a 1% concentration. Hemiamyloid reactions [K/I; Baral (1987)] were observed by treatment with a 10% aqueous solution of potassium hydroxide followed by Lugol s solution. The expression conidium is here used in a broad sense and includes the term spermatium or pycnospore. The term stroma was more or less anatomically interpreted and applied when brownish and rigid or carbonized interascal tissues were present. Key to the species 1 Ascospores only transversely septate, anisolocular, with large and rounded upper cell, μm A. ilicinum Ascospores submuriform to muriform, isolocular (1) Ascomata stromatic, all layers more or less brownish, ascospores muriform Ascomata not stromatic, ascigerous and hypothecioid layers colourless, ascospores submuriform or muriform (2) Asci K/I, thallus hyphae I+ blue, ascospores μm. 6. A. spectabile Asci with K/I+ blue ring, thallus hyphae I to yellowish, ascospores (15 ) μm A. ruanum 4(2) Lichen forming. Ascospores (23 )26 30( 33) (9 )10 13 μm, with a distinct, 1 μm thick gelatinous sheath A. taediosoides Not lichen forming. Ascospores usually smaller, without gelatinous sheath (4) Ascospores muriform, transverse segments with (2 )3 4 longitudinal septa, ascospores 18 22( 25) μm A. sardoum Ascospores submuriform, transverse segments with 0 1 longitudinal septum (5) Ascospores 18 28( 30) 8 13 μm, with I+ red outer walls. Hyphal tips in epithecioid layer more or less embedded in gel (A. lirellans) Ascospores (14 )15 18( 22) 6 9 μm, spore walls I. Hyphal tips in epithecioid layer more or less free A. crozalsianum

3 1996 Arthothelium Grube & Giralt 17 The Species 1. Arthothelium crozalsianum (de Lesd.) de Lesd. in Crozals, Ann. Soc. Hist. Toulon 10: 112 (1924). Arthonia crozalsiana de Lesd., Bull. Soc. Bot. France 54: 445 (1907); type: Algeria: Murdjajo près Oran, sur pins, 1907, A. de Crozals (US! lectotype, here selected). Nom. cons. prop. Arthothelium adriaticum Zahlbr., Ann. Mycol. 12: 337 (1914); type: Croatia, Dalmatia, Cazza, on Euphorbia dendroides, v 1911, A. Ginzberger (W! holotype). Arthothelium xylographoides Müll. Arg., Rev. Mycol. 6: 18 (1884); type: Egypt: ad ligna sicca fabrefacta telegraphi prope El Arish, 25 iii 1880, W. Barbey (G not seen, E! isotype).?arthothelium burolletii de Lesd., Bull. Soc. Bot. France 72: 790 (1925); type: Tunisia, Sousse, on Ailanthus glutinosa, 1922, Burollet (not found, probably destroyed during World War II). (Figs 1A, 2A B) Thallus effuse, whitish to pale grey, occasionally delimited by a black prothallus. No phycobiont. Ascomata irregularly rounded and mm diam. to rather elongate, 1 2( 4) mm, simple, branched or stellate, surface slightly raised above level of thallus, occasionally covered by a white pruina. Epithecioid layer olivaceous-brown, μm tall; cells c. 2( 3) μm wide, irregularly branched, tips free. Ascigerous layer hyaline, c μm tall. Hypothecioid layer colourless to pale brownish, 20 40( 60) μm tall. Interascal filaments anastomosing, branched towards the top, μm wide. Asci broadly clavate to subglobose, μm, 8-spored, with K/I+ bluish ring structure. Ascospores ellipsoid, persistently hyaline, without distinct gelatinous sheath, (14 )15 18( 22) 6 9 μm, submuriform, with 4 6 transverse septa and one longitudinal septum in each of 1 4 transverse segments, very rarely with two longitudinal septa in a transverse segment. Conidiomata common, scattered, roundish, more or less hemispherical. Conidia bacilliform, (4 ) μm. Chemical reactions: Ascomatal gel I+ blue, rapidly becoming blood-red, K/I+ blue. Brownish pigments K+ dark olivaceous. Life form: Apparently not lichenized; on smooth bark of various trees. Observations: The Crozals herbarium, including the type material of A. crozalsianum, was purchased by the Missouri Botanical Garden in 1933, but is now located in US (Washington). The original diagnosis of Bouly de Lesdain (1907), as well as the description given by Redinger (1937), fit all other specimens identified, including those labelled as A. adriaticum. For this reason we synonymize A. adriaticum with A. crozalsianum and not with A. sardoum as was done by Redinger (1937). Arthothelium crozalsianum and A. sardoum have often been confused and even treated as probable synonyms (e.g. Nimis & Poelt 1987). The present work shows that both taxa are distinct. Arthothelium xylographoides seems to be nothing more than a lignicolous morph of A. crozalsianum, with rather elongate ascomata. All other characters are identical in both species. Arthothelium xylographoides is an older name for the species; however, we proposed to conserve A. crozalsianum according to ICBN

4 18 THE LICHENOLOGIST Vol. 28 FIG. 1. Ascospores of: A, Arthothelium crozalsianum (Tunisia, near Hammamet, 1968, J. Poelt, GZU); B, A. sardoum (S isotype); C, A. taediosoides (BCC holotype). Scale=10 μm. Art. 14, since the latter name is commonly used, whereas A. xylographoides has rarely been applied. Arthothelium burolletii is most probably also a synonym of A. crozalsianum, but we could not trace the type for direct comparison.

5 1996 Arthothelium Grube & Giralt 19 FIG. 2. Arthothelium crozalsianum (Tunisia, near Hammamet, 1968, J. Poelt, GZU): A, submuriform ascospores; B, ascus with 8 ascospores. Scale=10 μm.

6 20 THE LICHENOLOGIST Vol. 28 Arthothelium crozalsianum is a well-delimited species, well characterized by the whitish and non-lichenized thallus, usually elongate and branched ascomata, and small submuriform ascospores with 1 4 transverse segments each subdivided by one longitudinal septum (a second septum is very rarely found). The original description of A. adriaticum (Zahlbruckner 1914) as well as the observations of Redinger (1937) concerning the presence of algae, are incorrect. Bouly de Lesdain (1907) did not mention this character in the original description of A. crozalsianum, and symbiotic algae were not seen in the material we examined. Among the other species treated, the species can be confused only with A. lirellans, which also has non-lichenized thalli and submuriform ascospores. The yellowish thallus, usually delimited by a dark prothallus, together with mostly rounded ascomata and larger ascospores, as well as anatomical characters of the ascomata, separate A. lirellans. Furthermore, the ecology of A. crozalsianum is markedly different from that of A. lirellans (see comments under A. lirellans). Habitat and distribution: Arthothelium crozalsianum is a maritime species, widely distributed along the western Mediterranean coasts. It grows on the smooth bark of several shrubs and trees, especially on Pinus halepensis, and is usually associated with other non-lichenized, pioneer species of Arthonia. In southern Spain and northern Africa the species seems to have a broader ecological amplitude and can also be found at more inland localities. In the Mediterranean, A. crozalsianum has been reported from Dalmatia (Zahlbruckner 1914), southern France (Redinger 1937), Italy (Nimis 1993), Sardinia (Nimis & Poelt 1987), Algeria (Bouly de Lesdain 1907), Morocco (Torrente & Egea 1987), Islas Baleares (Llimona 1976, as A. taediosum, Breuss 1988) and several times from Spain, e.g. Crespo & Atienza (1981), Torrente & Egea (1984), Gómez-Bolea (1985) and Giralt (1986, 1991). Selected specimens examined: France: Var: Faubregas, Colle Noire, 1923, A. de Crozals (US); Marvivo, near Les Sablettes, on Pinus halepensis, 1923, A. de Crozals (US). Italy: Toscana: Latium, Roma, Parco Nazionale del Circeo, Picco di Circe, 300 m, on Fraxinus ornus, 1984, P. L. Nimis (TSB); Livorno: Isola di Capraia, Il Porto, 4 5 m, on Nerium oleander, 1988, P. L. Nimis et al. (TSB); Sardinia: Sassari, Sta. Teresa di Gallura, Rena Maiore, 4 m, on Pistacia lentiscus, P. L. Nimis (TSB); Sicily: Ragusa, Kamarina, on Quercus calliprinos, 1987, M. Grillo (TSB); Isole Egadi, Marettimo, Sorgente, 180 m, on Morus, 1991, P. L. Nimis (TSB); Isole Pelagie, Lampedusa, 80 m, on Pistacia lentiscus, 1993, P. L. Nimis (TSB); Isole di Pantelleria, on Phillyrea, 1981, Loi (TSB). Spain: Andalucia: Almería, Cabo de Gata, El Sabinar, 50 m, on Opuntia ficus-indica, 1975, X. Llimona (BCC, GZU, S, US, W, as Vezda, Lich. sel. exs. 1302); Roquetas de Mar, Punta del Sabinar, 5 m, on Pistacia lentiscus, 1988, J. M. Egea & L. Alonso (MUB); Níjar, La Serrata, on Ceratonia siliqua, 1973, X. Llimona (BCC); Islas Baleares: Cabrera, L Espalmador, on Olea europaea, 1976, X. Llimona (BCC); Mallorca, Serra de Llevant, near Son Cervera, Puig de sa Font, 1987, O. Breuss (hb. Breuss); Catalonia: Girona, Alt Empordà, Les Torruelles, on Olea, 1981, A. Gómez-Bolea (BCC); Barcelona, Garraf, Olesa de Bonesvalls, 400 m, on Pinus halepensis, 1984, A. Gómez-Bolea (BCC); Tarragona, Tarragonès, Creixell, La Costa, on Ceratonia siliqua and Corylus avellana, 1984, M. Giralt (hb. Giralt); Ribera d Ebre, Tivissa, Barranc Franquès, 300 m, on Ceratonia siliqua, 1988, M. Giralt, A. Gómez-Bolea & P. Navarro (hb. Giralt); Baix Camp, Coll de Balaguer, on Ceratonia siliqua, 1984, A. Gómez-Bolea (BCC); Vandellós, Mola de Genessies, 500 m, on Pinus halepensis, 1988, M. Giralt, A. Gómez-Bolea & P. Navarro (hb. Giralt); Baix Camp, Colldejou, La Mola de Colldejou, 600 m, on Hedera helix, 1988, M. Giralt et al. (hb. Giralt); Murcia: El Palmar, Venta de la Paloma, on Pinus halepensis,

7 1996 Arthothelium Grube & Giralt , X. Llimona (BCC); Aguilas, Cabo Cope, 245 m, on Launaea arborescens, 1988, J. M. Egea & L. Alonso (MUB); Cartagena, Sierra de la Muela, Cabeza Colorada, 490 m, on Pinus halepensis, 1988, J. M. Egea et al. (MUB); Cabo de Palos, 30 km E of Cartagena, cala Reona, c. 2 m, 1987, J. Hafellner & J. M. Egea (GZU); San Pedro del Pinatar, on Pinus halepensis, 1977, X. Llimona (BCC); Beniaján, Sierra de Mirabete, El Puntal, on Pinus halepensis, 1980, X. Llimona (BCC); Riquelme, Sierra de Columbares, Columbares, on Nerium oleander, 1980, X. Llimona (BCC); País Valencià: Alacant, Jávea, Cap de San Antoni, 180 m, on Ceratonia siliqua, 1986, P. Torrente & J. M. Egea (MUB); Oriola, túnel de Oriola, on Pinus halepensis, 1977, X. Llimona (BCC); Alberic, Port d Alberic, on Pinus halepensis, 1977, X. Llimona (BCC); Elx, N of Elx, on Pinus halepensis, 1991, X. Llimona (BCC); Benidorm, Sierra Helada, Punta de la Escaleta, 330 m, on Ceratonia siliqua and Erica multiflora, 1987, J. M. Egea, P. P. Moreno & L. Alonso (MUB); Calpe, Penyó d Ifach, 332 m, on Pinus halepensis, 1987, J. M. Egea, P. P. Moreno & L. Alonso (MUB); Dunas de Guardamar, Guardamar de Segura, on Eucalyptus sp., 1982, J. M. Egea (MUB); Torrevieja, on Ceratonia siliqua, 1983 (MUB); Santa Pola, Cabo de Santa Pola, on Eucalyptus, 1983, J. M. Egea (MUB); Valencia, Cullera, Alto de la Caixa, on Pinus halepensis, 200 m, 1986, J. M. Egea & P. Torrente (MUB); Montanya de l Or, 233 m, 1986, J. M. Egea & L. Alonso (MUB); Dènia, Serra del Montgó, 300 m, on Ceratonia siliqua, 1986, J. M. Egea & P. Torrente (MUB); Camping Las Rotas, on Pinus halepensis, 1986, J. M. Egea & P. Torrente (MUB). Morocco: Melilla, Zaust, on Opuntia ficus-indica, 1967, X. Llimona (BCC); Nador, Cabo Tres Forcas, 100 m, on Lycium intricatum and Tetraclinis articulata, 1985, J. M. Egea (MUB). Algeria: Plateau de Murdjajo, near Oran, 500 m, on Pinus halepensis, 1906, A. de Crozals (US from the type locality); Ben Aissi, near Oran, 1909, A. de Crozals (US). Tunisia: near Hammamet, on Opuntia ficus-indica and Callitris quadrivalvis, 1968, J. Poelt (GZU, H, UPS). Sahara: El Aaiún, on Rhus, 1981, A. Crespo (GZU). 2. Arthothelium ilicinum (Taylor) P. James Lichenologist 3: 97 (1965). Arthonia ilicina Taylor in Mackay, Flora Hibernica 2: 105 (1836); type: Ireland, Kerry, upper Lakes of Killarney, on holly, 1834 (FH! holotype). (Fig. 3A) Thallus effuse, creamy white. Phycobiont Trentepohlia. Ascomata scattered, roundish to irregular in form, mm diam., μm tall, surface at the same level as thallus to slightly convex, dark brown or blackish brown, epruinose. Epithecioid layer brown, μm tall, often covered with a μm tall, occasionally disintegrated, hyaline gelatinous layer; hyphae mainly anticlinal, often collapsed and without plasma, brownwalled, branched and strongly sinuous, occasionally separated by portions of hyaline gel. Ascigerous layer hyaline to yellowish brown, μm, densely packed with asci. Hypothecioid layer hyaline to yellowish brown, μm tall. Interascal filaments anastomosing, branched towards the top, texture mostly difficult to discern due to heterogeneous interascal gel. Asci clavate, μm, 8-spored, apex with K/I+ elongated, bluish ring structure and paler bluish tholus flanks. Ascospores obovoid, hyaline and smooth, but pale brown and faintly verrucose when old, μm, with 5 6( 7) transverse septa, upper cell enlarged. Conidiomata roundish, brownish. Conidia bacilliform, μm. Chemical reactions: Ascomatal gel I+ blue, later becoming red in epithecioid layer, K/I+ blue. Brownish pigment in the epithecioid layer K+ olivaceous.

8 22 THE LICHENOLOGIST Vol. 28 FIG. 3. Ascospores of: A, Arthothelium ilicinum (Spain, Galicia, Ordenes-Gesteda, 1980, A. Crespo et al., MAF); B, A. spectabile (Iowa, NW of Luxemburg, 1965, C. M. Wetmore, GZU); C, A. lirellans (UPS lectotype); D, A. ruanum (Austria, Burgenland, Rudersdorf, 1989, J. Hafellner, GZU). Scale=10 μm. Life form: Lichenized; mainly on smooth bark, e.g., Corylus, also occurring on other trees, for example Abies. Observations: Arthothelium ilicinum is unique among the species treated here in having only transversely septate ascospores with a roundish upper cell. The closest relative to this species seems to be Arthonia ilicinella Nyl., which is

9 1996 Arthothelium Grube & Giralt 23 distinguished only by smaller ascomata and ascospores (Coppins, pers. comm.) and which was included in Arthothelium ilicinum by Redinger (1937, as Arthonia ilicina). Two other closely related taxa, also characterized by ascospores with an enlarged, roundish upper cell, are Arthothelium dictyosporum (Coppins & P. James) Coppins and A. macounii (G. Merr.) W. J. Noble [type: Vancouver Island, Sidney, on young firs, 20 i 1914, J. Macoun (FH! lectotype, Ahti et al. 1987). Syn. A. reagens (Coppins & P. James) Coppins & P. James]. Both are distinguished by the muriform ascospores, which become more distinctly warted when old, shorter conidia, and the latter species additionally differs in containing K+ purplish violet pigments. Arthothelium ilicinum and its relatives were studied by Coppins & James (1979) and Coppins (1992, as Arthonia ilicina). The placement of Arthothelium ilicinum into either Arthonia or Arthothelium is not clear. As already indicated in Richardson & Morgan-Jones (1964), the asci of A. ilicinum differ from those typical of Arthonia. Also the differences in ascoma anatomy further suggest that this species is not closely related to the core groups of Arthonia, i.e., species related to Arthonia radiata (Pers.) Ach. or to A. galactites (DC.) Dufour. Other European Arthonia species with macrocephalic ascospores are apparently not related to Arthothelium ilicinum. Arthonia cinnabarina (DC.) Wallr., A. elegans (Ach.) Almq., as well as species related to A. stellaris Kremp. (e.g., A. anglica Coppins, A. astroidestra Nyl.) have Arthonia-type asci and also differ in several other characters, e.g. distinct epithecium structures or elongate and branched ascomata. Arthothelium ilicinum seems to be more closely related to tropical species currently placed in either Arthonia or Arthothelium. Arthonia picea Vain., for example, has ascospores similar in size and shape, differing in a distinct verrucose ornamentation of old ascospores. However, A. picea is well characterized by reddish ascomata, which are completely interspersed by orange-red, crystalline pigments. Arthonia complanata Fée, with black ascomata, is widespread throughout the tropics and highly polymorphic. At least some morphs from Costa Rica have reduced K/I+ ring structures in the asci and persistently smooth ascospores (Grube, unpublished data). The species ought to be studied in greater detail, because some specimens are probably closely related to Arthothelium ilicinum. Another group of species with intermediate characters of Arthonia and Arthothelium was recently recognized as the genus Eremothecella Syd. (Sérusiaux 1992), including epiphyllous species. Eremothecella is characterized by very long conidia (up to 450 μm long), which, however, have not been found in certain species of the genus. At present, the relationship between Eremothecella and the Arthothelium ilicinum group (including A. dictyosporum, A. macounii and other similar species from the tropics) is not resolved. Habitat and distribution: Arthothelium ilicinum is an oceanic species, widely distributed along coasts of northern Europe, North America, as well as of South Africa, Tasmania (Coppins, pers. comm.) and of New South Wales (Kantvilas 1989), where it grows on smooth bark and is in Europe associated with other pioneer and oceanic species such as Graphis scripta and Enterographa crassa. In southern Europe it has been reported by Tavares

10 24 THE LICHENOLOGIST Vol. 28 (1945) from Portugal, by Vivant (1988) and Etayo (1989b) from the Atlantic Pyrenees, by López de Silanes & Carballal (1987) from Galicia (NW Spain), by Nimis (1993) from Calabria (Italy) and by Champion & Sanchez-Pinto (1978) from the Canary Isles. Its distribution shows that this species can occur in very humid and well-wooded Mediterranean forests. Together with Arthothelium macounii (as A. reagens) it has also been reported from Madeira by Kalb & Hafellner (1992). At least one record cited as Arthonia stellaris in Crespo et al. (1981) from NW Spain (cited below, from La Coruña, MAF), is actually A. ilicinum. Specimens examined: Italy: Calabria: Catanzaro, Serra San Bruno, Bosco di Sta. Maria, near La Certosa, 910 m, 1988, J. Poelt & P. L. Nimis (GZU, TSB). Portugal: Estremadura: Serra de Sintra, Pena, Sta. Eufemia, on Ilex aquifolium, c. 250 m, 1946, C. N. Tavares (US, as Tavares, Lich. Lus. sel. exs. 78); Serra de Sintra-Parque de Pena, on Ilex aquifolium, 1944, C. N. Tavares (LISU); Serra da Pinta, on Quercus, 1943, C. N. Tavares (LISU). Spain: Galicia: La Coruña, Ordenes-Gesteda, Río Beduido, on Alnus and Quercus, 1980, A. Crespo et al. (MAF); Navarra: Ibardín, on Quercus sp., 300 m, 1987, J. Etayo (hb. Etayo); Señorío de Bértiz, on Ilex aquifolium, 200 m, 1987, J. Etayo (hb. Etayo). Selected extramediterranean specimens examined: Canada: British Columbia: Queen Charlotte Islands, Graham Island, Gudal Bay, on Alnus sinuata, 1967, I. M. Brodo, M. J. Shchepanek & W. B. Schofield (GZU, as Lich. Can. Exs. 5). Great Britain: Scotland: Westerness, Ardnamurchan Peninsula, c. 30 m, on Corylus, 1992, B. Coppins, P. W. James & J. Poelt (GZU). 3. Arthothelium lirellans (Almq.) Coppins Lichenologist 11: 28 (1979). Arthonia lirellans Almq., Kongl. Sv. Vetenskapakad. Handl. 17: 40 (1880); type: Ireland, Killarney, Cromaglown, 1864, I. Carroll (UPS! lectotype). (Fig. 3C) Thallus inconspicuous. No phycobiont. Ascomata roundish to elongate and branched, c mm, surface level with thallus, blackish, c μm tall. Epithecioid layer brownish to olivaceous brown, μm tall, often with integrated bark fragments; hyphae 2 5 μm wide, embedded in gel. Ascigerous layer colourless, c μm tall, gel not homogeneous and often interspersed with amorphous olivaceous brown pigments. Hypothecioid layer colourless, 0 10 μm tall. Interascal filaments anastomosing, infrequently branched at the top; cells c μm. Asci broadly clavate, μm, 8-spored, with very faint K/I+ bluish tube in the tholus. Ascospores obovoid, persistently hyaline, 18 28( 30) 8 12 μm, with 5 7 transverse septa and one longitudinal septum in 0 3 transverse segments; spore-walls I+ reddish. Conidiomata roundish, brownish. Conidia bacilliform, μm. Chemical reactions: Ascomatal gel I+ and K/I+ blue. Brownish pigments K+ dark olivaceous. Life form: Not lichenized; on smooth bark (e.g. of Corylus). Observations: Arthothelium lirellans is well characterized by its nonlichenized, yellowish thallus, usually delimited by a dark prothallus, irregularly

11 1996 Arthothelium Grube & Giralt 25 rounded to slightly elongated and branched ascomata, and submuriform ascospores with one longitudinal septum in 0 3 transverse segments, and I+ reddish spore-walls. Furthermore, its interascal filaments are infrequently branched and anastomosing and the hyphal tips in the epithecioid layer are embedded in gel, differing from the richly branched and anastomosed filaments with more-or-less free hyphal tips in the epithecioid layer of the A. sardoum group. The two other species with submuriform spores in this study are clearly distinghished: A. crozalsianum has significantly smaller ascospores and A. taediosoides has a distinctly lichenized thallus. Another anatomically similar taxon is A. orbilliferum (Almq.) Hasse (compare Coppins & James 1979). The record of A. lirellans from southern Europe reported by Etayo (1989a) refers to an Arthonia species, as it has a lichenized thallus, brown hypothecioid layer and only transversely septate ascospores that become brown at maturity. Habitat and distribution: Arthothelium lirellans is a suboceanic species, common in W Britain and Scotland (Coppins 1992). The species is found also in Madeira (Kalb & Hafellner 1992) and may occur along the Atlantic coast of the Iberian Peninsula. For that reason it is also treated in this paper and included in the key in brackets. As typical for many arthonioid species, A. lirellans grows on smooth bark of deciduous trees. Selected extramediterranean specimens examined: Austria: Burgenland: S of Tschaterberg, 1 km NW of Stausee, 250 m, on Carpinus, 1992, J. Hafellner & W. Maurer (GZU); Carinthia: Drautal, on Alnus incana, 1988/89, W. Petutschnig (GZU); Styria: S Kranach, WSW Gamlitz, 1991, M. Giralt & J. Poelt (GZU). Ireland: Kerry: South Kerry, Munster, Glencar, 1864, I. Carroll (UPS); Argyll Main, S of Taynuilt, Glen Nant, near Tailor s Leap, on Corylus avellana, 1980, B. J. Coppins (GZU). 4. Arthothelium ruanum (A. Massal.) Körb. Parerga Lich.: 263 (1861). Arthonia ruana A. Massal., Ric. Auton. Lich. Crost.: 49 (1852); type: (M! isotype, locality not indicated). (Fig. 3D) Thallus effuse, greenish, greyish brown to yellowish grey, developed in the uppermost bark layers, algal layer below the bark surface. Phycobiont Trentepohlia, cells scattered, ellipsoid to almost spherical, c μm, in chains. Ascomata roundish to irregular, c mm diam., surface level with thallus, rarely becoming slightly elevated, black; often disintegrating when large; surface rough, often covered by bark remains, often cracked. Epithecioid layer carbonized, brown, μm tall, cells c. 2μm wide, anastomosing and branched, pigments in outer cell walls and intercellular spaces. Ascigerous layer hyaline to pale brown by granular, intercellular pigments, c μm tall; in some regions with densely packed asci. Hypothecioid layer brown, c μm tall, cells rather dense, c. 2 4 μm wide. Interascal filaments anastomosing, infrequently branched, with dominant vertical elements. Asci broadly clavate, μm, shortly stipitate, 8-spored, with elongated, K/I+ blue ring-structure. Ascospores slightly obovoid, hyaline to

12 26 THE LICHENOLOGIST Vol. 28 pale brown and faintly warted when old, occasionally with sharply bordered sheath (especially when enclosed in asci), (15 ) μm, with 5 7 transverse septa and 1 3 longitudinal septa in each transverse segment. Conidiomata common at the periphery of the thalli, roundish, hemispherical, brownish. Conidia bacilliform, μm. Chemical reactions: Ascomatal gel I+ blue or immediately blood-red. Brownish pigments K+ dark olivaceous. Thallus hyphae K/I+ faintly bluish, ascomatal gel K/I+ blue. Life form: Lichenized; on smooth bark. Observations: The carbonized epithecioid and hypothecioid layers are diagnostic for A. ruanum, which can also be distinguished from A. spectabile by more closely spaced asci, arranged in more or less distinct groups. The species is homogeneous, except for some variability in the iodine reaction. While the isotype has I+ reddish, K/I+ bluish outer spore walls, this character was not found in other specimens. A closely related taxon is A. norvegicum Coppins & Tønsberg, but its ascomata are more irregular in outline and convex and its ascospores larger, with more transverse septa (Coppins & Tønsberg 1984). Arthothelium norvegicum has been recently reported from Madeira by Kalb & Hafellner (1992). Habitat and distribution: Arthothelium ruanum is a suboceanic species, scattered but widely distributed in Europe from Scandinavia to the south of Italy. It occurs in sheltered woodlands where it grows on smooth bark of deciduous trees. From the study area it has been reported by Vezda & Vivant (1973) and Etayo & Gómez-Bolea (1992) from the Atlantic Pyrenees, by Etayo (1990) from the Basque Country, by Carballal & Garcia Molares (1987) from Galicia (NW Spain) and by Nimis (1993) from Italy. Specimens studied: France: Pyrénées Atlantiques: Sainte Engrâce, Arpideko Ibarre, on Salix, 1993, J. Etayo (hb. Etayo). Italy: Prealpi Giuli: Valle del Torre, Musi, 650 m, on Juglans, 1989, Castello, Gasparo & Tretiach (TSB). Spain: Galicia: Pontevedra, Vigo city, on Robinia pseudoacacia, 1985, R. Carballal et al. (SANT); Navarra: Iribas, on Corylus avellana, 650 m, 1988, J. Etayo (hb. Etayo); Señorío de Bértiz, on Alnus glutinosa, 1988, J. Etayo (hb. Etayo); Goizueta, on Corylus avellana, 200 m, 1988, J. Etayo (hb. Etayo). Selected extramediterranean specimens examined: Austria: Burgenland: 2 km E of Rudersdorf, on Corylus avellana, 280 m, 1989, J. Hafellner (GZU). Germany: Mecklenburg, 1975, R. Doll (GZU); Württemberg, Maldenbachtal, on Fraxinus, 1948, E. Putzler (GZU). Great Britain: England: East Sussex: Tunbridge Wells, on Corylus avellana, 1973, B. J. Coppins & F. Rose (BCC, GZU, as: Vezda, Lich. sel. exs. 1703). Poland: Beskid Niski Mountains, Bukowica Range, Tokarnia Mountain, near Wola Piotrowa, 550 m, on Alnus incana, 1974, J. Nowak & M. Olech (GZU). Sweden: Uppland: Vange Kirchspiel, on Populus tremula, 1989, R. Santesson & J. Poelt (GZU). Switzerland: Zürich, 1977, G. Winter (GJO). 5. Arthothelium sardoum Bagl. N. Giorn. Bot. Ital. 11: 109 (1879). Arthonia sardoa (Bagl.) H. Olivier, Bull. Géogr. Bot.: 185 (1917); type: Italy, Sardinia, Capoterra, Canepa (S! isotype). (Figs 1B, 4A C)

13 1996 Arthothelium Grube & Giralt 27 FIG. 4. Arthothelium sardoum (Spain, Tarragonès, La Costa, 1984, M. Giralt, Hb. Giralt): A C, muriform ascospores. Scales=10 μm.

14 28 THE LICHENOLOGIST Vol. 28 Thallus effuse, whitish. No phycobiont. Ascomata scattered, roundish to slightly elongate, c. 0 4 mm, on same level as the thallus, blackish, matt, in section c μm tall; occasionally, with irregularly distributed yellowish purple grains. Epithecioid layer olivaceous brown, μm tall; cells c. 2 μm wide, irregularly branched, hyphal tips more or less free. Ascigerous layer colourless, c. 30 μm tall. Hypothecioid layer colourless to pale brownish, μm tall. Interascal filaments anastomosing, richly branched at the top, c. 1 μm wide. Asci broadly clavate to subglobose, μm, with K/I+ bluish ring-structure. Ascospores obovoid, hyaline, becoming pale brown, 18 22( 25) μm, muriform, with 5 8 transverse septa and (1 )2 3( 4) longitudinal septa in each transverse segment. Conidiomata common, roundish, more or less hemispherical, brownish. Conidia bacilliform, straight or curved, (4 ) μm. Chemical reactions: Ascomatal gel I+ persistently blue, K/I+ blue. Brownish pigments K+ dark olivaceous. Yellowish purple pigments, if present, K+ purplish violet. Life form: Apparently not lichenized; on smooth bark of various trees. Observations: Arthothelium sardoum is characterized by a whitish, nonlichenized thallus, rounded to shortly elongate ascomata and obovoid muriform ascospores, with 1 3( 4) longitudinal septa in each transverse segment. This species often contains ascomatal pigments that react purplish violet in alkaline solutions. Similar reactions can be found in other species, or morphotypes of species, that occur in Europe, for example in A. macounii. Some specimens (in GZU) of A. scandinavicum Th. Fr. also produce a K+ purplish violet reaction. Beside the differences in the ascomatal structure, these species are distinguished from A. sardoum by ascospore characters. Arthothelium scandinavicum has significantly larger ascospores (up to μm) and those of A. macounii have an enlarged upper cell. A pale K+ purplish reaction of the epithecioid layer can also be found in A. spectabile, which is distinguished by a more-or-less stromatic ascomatal structure. Among the species treated, only A. ruanum has ascospores similar to those of A. sardoum, but A. ruanum is distinctly lichenized and the hypothecium is dark coloured. Similar ascospores are seen also in A. orbilliferum, but this species clearly deviates in other ascomatal characters. Arthothelium sardoum is closely related to A. crozalsianum and is similar in thallus appearance, ascospore shape, epithecioid texture, interascal filaments and ascomatal pigmentation. However, the latter species differs in having more elongate and branched ascomata that are often pruinose, and smaller and persistently colourless ascospores with fewer transverse and longitudinal septa. Habitat and distribution: At present, A. sardoum is known only from a few localities along the western Mediterranean coast. The collections indicate that it grows on smooth bark of several shrubs and trees in coastal sites, very often

15 1996 Arthothelium Grube & Giralt 29 on Ceratonia siliqua. The lichen is often associated with other thermophilous Mediterranean species belonging to the lichen association Dirinetum ceratoniae, including Dirina ceratonia, Arthonia melanophthalma and Schismatomma picconianum, and with other more widely distributed pioneer species such as Lecidella elaeochroma and Lecanora subfusca agg. From the Mediterranean area it was repeatedly reported from Italy (Nimis & Poelt 1987; Nimis 1993) and from Catalonia (Spain) by Giralt (1986, 1991). Some specimens of A. sardoum were named by Torrente & Egea (1984) as A. crozalsianum. The records in Gómez-Bolea (1985) refer to A. taediosoides. Selected specimens examined: France: Var: Port Cros, on Phillyrea, 1924, A. de Crozals (US); San Peire, on Ficus carica, 1924, A. de Crozals (US); Marvivo near Les Sablettes, on Pinus halepensis, 1924, A. de Crozals (US). Italy: Calabria: Nicotera, c.2m, on Pinus, 1990, P. L. Nimis (TSB). Spain: Andalucia: Almería, Roquetas de Mar, Punta del Sabinar, 5 m, on Pistacia lentiscus, 1988, J. M. Egea & L. Alonso (MUB); Catalonia: Barcelona, Anoia, La Llacuna, Riera de Riudebitlles, 550 m, on Prunus sp., 1988, M. Giralt, A. Gómez-Bolea & P. Navarro (hb. Giralt); Tarragona, Tarragonès, Creixell, La Costa, 30 m, on Ceratonia siliqua, 1984, M. Giralt (hb. Giralt); Baix Camp, Mont-Roig, Ermita de Peiró, 150 m, on Ceratonia siliqua, 1987, M. Giralt, X. Llimona & P. Navarro (hb. Giralt); Ribera d Ebre, Tivissa, Barranc Franqués, 350 m, on Ceratonia siliqua, 1987, M. Giralt & P. Navarro (hb. Giralt); Alt Camp, Esblada, Querol, 600 m, on Amelanchier ovalis, 1988, M. Giralt (BCC); Alt Camp, Aiguamurcia, Mas d en Bosch, 600 m, on Pinus halepensis, 1988, M. Giralt (hb. Giralt); Baix Camp, Vandellós, Barranc dels Avellans, 450 m., on Quercus ilex, 1988, M. Giralt (BCC); Baix Ebre, Tivenys de Mar, Barranc de les Petxines, 80 m, on Ceratonia siliqua, 1988, M. Giralt, A. Gómez-Bolea & P. Navarro (BCC); Alt Camp, Montferri, Ermita de Sant Marc, 250 m, on Ceratonia siliqua, 1990, M. Giralt (hb. Giralt); Murcia: Alto de las Hermanillas, on Ceratonia siliqua, 1983, J. M. Egea (MUB); País Valencià: Alacant, Jávea, Cap de San Antoni, 180 m, on Ceratonia siliqua, 1986, P. Torrente & J. M. Egea (MUB); Castelló, Vinarós, rambla del Cervól, 50 m, on Nerium oleander, 1990, M. Boqueras (BCC). Morocco: Bouznika, between Casablanca and Rabat, Playa de Abssanaoubar, 5 m, on Olea, 1984, J. M. Egea (MUB); Kénitra, N of Rabat, Forest of Mamora, 100 m, on Eucalyptus sp., J. M. Egea (MUB). Algeria: Murdjajo, near Oran, 1906, A. de Crozals (US, together with isolectotype of A. crozalsianum); Ben Aissi near Oran, 1909, A. de Crozals (US). 6. Arthothelium spectabile A. Massal. Ric. Auton. Lich. Crost: 54 (1852); type: Italy, Val Cherpa, Bolca, ad Corylus, 1869, Massalongo s.n. (VER! lectotype, selected by Tehler 1990). (Fig. 3B) Thallus effuse, greyish white to greenish grey, mostly lacking a distinct prothallus, in section c μm tall, an upper c. 30 μm thick layer without algae. Phycobiont Trentepohlia, cells c.12 7μm, in branched chains. Ascomata spot-like to somewhat angulate, up to 2 mm diam., surface level with thallus, sometimes slightly convex, blackish, with rough surface; old ascomata often separated from surrounding thallus parts by a narrow slit. Epithecioid layer pale to dark reddish brown, up to 80 μm tall, often with integrated bark fragments, cells largely gelatinized. Ascigerous layer brownish, up to 150 μm tall, pigments unevenly distributed. Hypothecioid layer brownish, c. 50 μm tall, with bark fragments. Interascal filaments anastomosing and branched, well developed and densely entwining the asci, elsewhere scattered, without preferred orientation, sinuous and c. 1 5 μm wide. Asci scattered, subglobose, μm, shortly stipitate, 8-spored, lacking K/I+ blue

16 30 THE LICHENOLOGIST Vol. 28 structures in the asci. Ascospores ellipsoid, rarely obovoid, hyaline, c μm, with 5 7 transverse and 1 3 longitudinal septa in each transverse segment. Conidiomata and conidia not seen. Chemical reactions: Thallus hyphae I+ bluish, ascomatal gel I+ red, K/I+ blue; pigments of epithecioid layer pale K+ purplish, remaining in gel, other pigments unchanged. Life form: Distinctly lichenized; on smooth bark. Observations: Arthothelium spectabile, the type species of the genus Arthothelium, is readily characterized by the stromatic structure of its ascomata. This and other characters support the proposed exclusion of the genus Arthothelium from the Arthoniales by Tehler (1990). However, the stromatic structure in this species is different from the type of stroma often seen in other fungal orders (e.g. Leotiales, Myriangiales) and consists of elongate cells that are strongly conglutinate by abundant brownish gel. It is also different from the stromatic texture of A. ruanum which is formed of shorter and denser cells. The asci are irregularly distributed and widely spaced in the stroma and they leave holes after ascospore ejection. Habitat and distribution: Arthothelium spectabile is a suboceanic species and from the Mediterranean it is so far known only from Slovenia (Redinger 1937) and from Italy (Redinger 1937; Nimis 1993). It has also been reported from the Canary Islands by Champion & Sanchez-Pinto (1978) and Gil González et al. (1990). The species is also known from North America, where it is widespread in temperate regions. Specimens examined: Croatia: Istria, Montonaer Forst, 1873, Flotow (GJO). Slovenia: Krakovski Gozd, 160 m, on Quercus robur, 1988, Tretiach (TSB). Selected extramediterranean specimens examined: Austria: Vienna: Dornbarker Park, 1870, L. Glowacki (GJO). Germany: Karlsruhe, Durlacher Wald, 1859, Bausch (GJO). Hungary: Banatu: Thermas Herculis, on Carpinus orientalis, 1874, Lojka (GJO). Poland: Oderwald near Brieg, 1898 (GJO). U.S.A., South Carolina: H. W. Ravenel (GZU, distr. as Reliquiae Tuckermanianae 8); Iowa: Dubuque County, NW of Luxemburg, 1965, C. M. Wetmore (GZU). 7. Arthothelium taediosoides Giralt & Grube sp. nov. A speciebus simillimis, A. sardoum et A. crozalsianum, differt thallo lichenisato; cellulae algarum globosae, 5 7( 10) μm magnae. Etiam differt ascosporis maioribus, μm, tunica gelatinosa distincta circumdatis. Typus: Hispania, Catalonia, Baix Ebre (Tarragona), L Ametlla de Mar, Mas Rabosenc, 100 m, in Ceratonis siliquae, 1988, M. Giralt, A. Gómez-Bolea & P. Navarro (BCC holotypus, GZU isotypus). (Figs 1C, 5A B) Thallus usually rather thick and well developed, continuous or discontinuous, smooth to more or less cracked, whitish, without a perceptible prothallus.

17 1996 Arthothelium Grube & Giralt 31 FIG. 5. Arthothelium taediosoides (BCC holotype): A B, submuriform to muriform ascospores with distinct gelatinous sheath (arrows). Scale=10 μm. Phycobiont chlorococcoid (Chlorella?), cells densely packed, c. 5 7( 10) μm diam. Ascomata irregularly rounded, stellate to elongate and more or less branched, ( 0 5) ( 2) mm, surface level with thallus, black, sometimes covered with a white pruina. Epithecioid layer olivaceous brown, μm tall, cells c. 2 μm wide, irregularly branched, with more-or-less free hyphal tips. Ascigerous layer colourless, c μm tall. Hypothecioid layer colourless to pale brownish, μm tall. Interascal filaments anastomosing, branched towards the top, c. 1 μm wide. Asci broadly clavate to subglobose, ( 35) μm, with K/I+ bluish ring-structure. Ascospores obovoid to ellipsoid, persistently hyaline, always with distinct gelatinous I+ red sheath, (23 )26 30( 33) (9)10 13 μm, submuriform to muriform, with 6 8 transverse and 1 2 longitudinal septa in each transverse segment. Conidiomata very rare, roundish, more or less hemispherical, blackish brown. Conidia bacilliform, straight or slightly curved, (4 ) μm. Chemical reactions: Ascomatal gel I+ blue becoming blood red, K/I+ blue. Brownish pigments K+ olivaceous. Life form: Distinctly lichenized; on smooth bark.

18 32 THE LICHENOLOGIST Vol. 28 Observations: This species is characterized by the whitish, well-developed and lichenized thallus, with comparatively small algal cells, which are chlorococcoid rather than trentepohlioid, as well as elongate ascomata and large submuriform to muriform ascospores that are persistently hyaline and have a distinct gelatinous sheath reacting I+ reddish. Among the species treated, A. taediosoides can be mistaken only for A. lirellans, which has a non-lichenized thallus and a different ecology. Arthothelium ilicinum, A. ruanum and A. spectabile, also with lichenized thalli, are distinguished by anatomical characters of the ascomata and ascospores. The new taxon is separated from the related species, A. sardoum and A. crozalsianum, by its lichen-forming thallus and larger ascospores. Arthothelium taediosoides could have been placed in the genus Allarthothelium (Vain.) Zahlbr., according to some former concepts, as the thallus contains coccoid green algae. However, except for the life form, Arthothelium taediosoides is closely related to A. crozalsianum or A. sardoum. These three species are much more closely linked to the core group of Arthonia than to Arthothelium s.str. In his treatment of European species, Redinger (1937) included A. taediosum (Nyl.) Müll. Arg., described from Chile and cited only one European specimen from Portugal (Mafra, Jorge-1846, W). Our re-examination of the material from herbarium W revealed that it consists of two Arthonia species but Arthothelium was not found. Corresponding material in herbarium USA, however, belongs to A. taediosoides. Arthothelium taediosum differs from A. taediosoides in larger, strongly muriform ascospores that become brownish with age. Redinger (1937) also included A. lirellans in A. taediosum, but Coppins & James (1979) already pointed out that this was clearly wrong. Habitat and distribution: Arthothelium taediosoides is a maritime species that shows a scattered distribution throughout NE Spain. It occurs at low altitudes in coastal localities with a typical Mediterranean climate, including open maquis or woodlands (degraded stages of Quercus ilex forests). The species grows on smooth bark of usually evergreen trees and shrubs, mainly on Ceratonia siliqua, associated with other pioneer species belonging to the Lecanorion subfuscae. From the Iberian Peninsula it has been reported already as A. taediosum by Crespo & Atienza (1981) and Giralt (1986), as A. aff. taediosum by Giralt (1991), as A. sardoum by Gómez-Bolea (1985) and as Arthothelium sp. 1 by Boqueras (1993). The record in Llimona (1976) refers to A. crozalsianum and that in Carballal et al. (1985) probably to an Arthonia sp. (López de Silanes in litt.). Additional specimens examined: Portugal: Lisboa, Mafra, 1920, A. R. Jorge (US, as Sampaio, Lich. Portugal 21). Spain: Catalonia: Girona, Alt Empordà, Les Torroelles, on Celtis australis, 1981, A. Gómez-Bolea (BCC); Tarragona, Tarragonès, Creixell, La Costa, 30 m, on Corylus avellana, 1984, M. Giralt (hb. Giralt); Roda de Berà, La Barquera, 25 m, on Corylus avellana, 1984, M. Giralt (hb. Giralt); Bonastre, Cal Lluïset, 200 m, on Ceratonia siliqua, 1984, M. Giralt (BCC); Plana de Peu, 290 m, on Ceratonia siliqua, 1990, M. Giralt (hb. Giralt); La Pobla de Montornès, Ermita de Santa Maria, 50 m, on Ceratonia siliqua, 1984, M. Giralt (hb. Giralt); El Catllar, Mas Sordé, 40 m, on Ceratonia siliqua, 1984, M. Giralt (BCC); Tarragona, Punta de la Mora, c. 25 m, on Quercus coccifera, 1987, M. Giralt (hb. Giralt); Tarragona, Mas de n Casido, c. 50 m, on Quercus ilex and Quercus coccifera, 1987, M. Giralt (hb. Giralt); Baix Ebre, L Ametlla de Mar, Mas Rabosenc, 100 m, on Ceratonia siliqua, 1988, P. Navarro, A. Gómez-Bolea &

19 1996 Arthothelium Grube & Giralt 33 TABLE 1. Characters of the studied Arthothelium species Species Ascoma structure Hyphal tips of epithecioid layer Hemiamyloid reaction of asci Spore type A. ilicinum Stromatic, with filiform cells A. lirellans (incl. A. orbilliferum) Stromatic, with filiform cells A. ruanum Stromatic, with thick, roundish cells A. sardoum, A. crozalsianum, and A. taediosoides Not stromatic, with filiform cells A. spectabile Stromatic, with filiform cells In gel In gel Carbonized and crumbly Elongated ring, pale flanks Pale elongated ring Elongated ring Distinctly obovoid, anisolocular Obovoid, isolocular Obovoid to ellipsoid, isolocular Free Ring Obovoid to ellipsoid, isolocular In gel No reaction (Obovoid to) ellipsoid, isolocular M. Giralt (hb. Giralt); Pedra Blanca, 100 m, on Prunus sp., 1988, P. Navarro, A. Gómez-Bolea & M. Giralt (hb. Giralt); Cap Roig, on Ceratonia siliqua, 1983, A. Gómez-Bolez (BCC); Tibenys, Barranc de les Petxines, 80 m, on Ceratonia siliqua, 1988, P. Navarro, A. Gómez-Bolea & M. Giralt (hb. Giralt); Tortosa, Serra del Cardó, Barranc de les Coves, 100 m, on Ceratonia siliqua, 1991, M. Boqueras (hb. Boqueras); Montsianès, La Galera, 150 m, on Olea europaea, 1985, M. Boqueras & A. Gómez-Bolea (hb. Boqueras); País Valencià: Valencia, Alcira, La Murta, on Olea europaea, 1981, V. Atienza (MAF); Carcagente, on Ceratonia siliqua, 1980, V. Atienza (MAF). Discussion In the genus Arthothelium we recognize five groups among the Mediterranean species (see Table 1). The A. spectabile group is characterized by stromatic ascomata with strongly gelatinized hyphal elements and more or less scattered asci. The A. ruanum group also has stromatic ascomata but with wider interascal filaments, a carbonized interascal matrix and closely spaced asci. Arthothelium sardoum, A. taediosoides and A. crozalsianum form a third group (A. sardoum group) of species that have affinities to the genus Arthonia. These species are presumably related to the Arthonia radiata or the A. galactites group, and even to A. granosa de Lesd., which has large, only one-septate ascospores, but laterally thick-walled asci. A fourth group is represented by Arthothelium ilicinum. Although the ascospores are transversely septate, the species appears to be related to A. dictyosporum (compare Coppins 1992: 94). Both have ascospores with a cephaloid proximal cell, but the distal ascospore cells are muriform in A. dictyosporum. Another useful character for defining species groups is the texture of the ascomata, as previously evaluated by Tehler (1990). Arthothelium spectabile has a unique ascoma structure: interascal filaments (paraphysoids) are usually concentrated around the asci and often collapsed in other parts of the ascomata (seen in lactophenol-cotton-blue treated preparations). The

20 34 THE LICHENOLOGIST Vol. 28 interascal filaments of A. spectabile are irregular and sinuous by comparison to those in A. ruanum with predominantly anticlinally orientated hyphae. The relationships of A. lirellans (and A. orbilliferum) to other species are not yet fully clarified, but the species seems to be more closely related to Arthonia species than to A. spectabile, regarding anatomical characters. The example of A. ilicinum and the related A. dictyosporum underlines the artificial aspect of the current concept of Arthonia and Arthothelium if these genera are based solely on ascospore septation. This is also evident by collections of an Arthonia radiata morph occasionally with longitudinal septa in the ascospores (Spain, Castelló, Plana Alta, Rambla de la Viuda, between Alcora and Benadressa, 100 m, on Nerium oleander, 1988, M. Boqueras, BCC). A similar situation is apparent in A. punctiformis: Arthonia malicola de Lesd., a species known only from the type locality in northern France (Bouly de Lesdain 1910; DUKE! isotype), is very similar to A. punctiformis (Pers.) A. Massal. and was included in the genus Arthonia by Redinger (1937) even though it possesses submuriform ascospores. Our observations confirm that the genus Arthothelium is heterogeneous. At least, the A. sardoum group might be included in Arthonia in future contributions. New characters, particularly the hyphal texture of the ascomata can be useful for re-evaluating the relationships between the taxa of the Arthoniales with low thallus organization. However, taxonomic consequences are premature until more species currently placed in Arthothelium are studied, especially those occurring in tropical regions. Excluded Species Arthothelium crenulatum de Lesd. Bull. Soc. Bot. France 74: 438 (1927). Allarthothelium crenulatum (de Lesd.) Redinger, Kryptfl. Deutschlands 9, 2(1): 168 (1937); type: France, Var, Dardennes, sur calcaire, 1926, A. de Crozals (US! isotype). The ascomata of Arthonia crenulatum have distinct, carbonized excipula and fissitunicate asci resembling the Dothidealean type. Up to now only one additional collection of this species is known (see also Navarro-Rosinés 1992). Specimen examined: Spain: Catalonia: Tarragona, Tarragonès, Vila-seca i Salou, Cap de Salou, 30 m, on limestone, 1986, N. L. Hladun, X. Llimona & P. Navarro-Rosinés (BCC). Arthothelium taediosum (Nyl.) Müll. Arg. Flora 63: 287 (1880). Arthonia taediosa Nyl., Ann. Soc. Nat. sér. 4, 3: 171 (1855); type: Chili (H-NYL 5688! lectotype, here selected, PC! isolectotype). This species was originally described from Chile and is characterized by large ( μm) and strongly muriform ascospores that become brown-walled with age. We have not seen comparable material from the Mediterranean. The material from Northern America collected by various lichenologists is neither conspecific with the type nor with European material determined as A. taediosum. The material from Portugal cited as A. taediosum by Redinger (1937) does not belong to this species (see also above).