Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 19 eluded from the genus and the new combinations, Psilolechia clavulifera (Nyl.) and Bacidia prasinata (Tuck.), are proposed. Keys for the identification of all the accepted European taxa are given. The taxonomic parts are preceded by an outline of the historical background to the study of Micarea, and details of materials and methods employed in this study. Detailed accounts of the morphology, chemistry, and ecology in the genus are provided , and a discussion of distributions is supported by maps for the British taxa. All Micarea species occur on acidic, nutrient poor substrata, and most are confined to cool-temperate, boreal, or oceanic regions; a few occur in arctic-alpine areas but the genus is poorly represented in dry, lowland, Mediterranean regions. Prior to this study, most of the species were little-known or misunderstood; clarification of their taxonomy has been achieved by paying particular attention to their anamorphic states, chemistry (including pigmentation), and detailed anatomy. Consideration of the distribution and ecology of the species has proved invaluable in ordering the taxonomic chaos which previously surrounded the notoriously variable species of the genus. Lecideaceae Historical background Until recently the circumscription of the Lecideaceae (and of the genera within it) had changed httle from that adopted by Zahlbruckner (1926). It included most Uchens with the following combination of characters: a crustose to squamulose thallus, a 'grass-green' phycobiont (excluding Trentepohlia and Phycopeltis) , ± immersed to sessile, disc-like apothecia without a thalhne margin, mainly colourless spores, and an absence of parietin (or related pigments) and (or) polarilocular spores. The principal genera in the family (e.g. Lecidea, Catillaria, Bacidia, Biatorella, Mycoblastus, Lopadium, Bombyliospora, and Toninia) were separated mainly on the basis of spore characters, i.e. size, septation, and number per ascus. This classification largely ignored many features which (according to modern mycological concepts) now merit careful consideration, although they were used to varying degrees for the delimitation of species or infrageneric categories above this rank. In brief, these features involve the structure of asci, excipular and hypothecial tissues, paraphyses and anamorphs, ontogeny, finer aspects of thallus structure, and nature and location of pigments and lichen substances. In addition, investigations of the phycobiont(s) and considerations of ecology and phytogeography often provide valuable supplementary information. However, the use of some of these features in an attempt to define more natural genera is not a purely recent phenomenon. Several lichenologists working in the 1850s and 1860s made bold attempts in this direction. With regard to the Lecideaceae s. lat., two lichenologists deserving special mention are G. W. Korber (who introduced Lecidella, Lopadium, Pyrrhospora, Schaereria, Schadonia, and Steinia) and A. B. Massalongo (who introduced Catillaria, Psilolechia, Sarcosagium, Scoliciosporum, Strangospora, and Toninia). In the latter half of the 19th century lichenology came under the almost monarchical influence of William Nylander, whose simplistic generic concepts gained precedence over the more far-sighted works of Korber, Massalongo, and others. From the 1870s right up to the 1950s there were few attempts to reassess the generic concepts of Nylander or the slightly more complex, but no less artificial, system of Zahlbruckner. Between about 1929 and 1954 the French lichenologist M. G. B. Choisy resurrected many of the old and more or less forgotten genera, and created several new ones (e.g. Haplocarpon [= Huilia], Hypocenomyce, Trapelia, and Tremolecia). Unfortu- nately, Choisy's works made little impact at the time and it was not until the mid-1960s that lichenologists began to look more carefully at the delimitation of genera. Recent investigations have led to the reinstatement (although often with emendations) of many of these genera and many new genera have had to be described (e.g. Fuscidea, Herteliana, Melanolecia, Trapeliop- sis, Tylothallia, and Vezdaea). Most are included in the key to European lichen genera in Poelt & Vezda (1981). Despite the many advances made during the last 15 years, it will be several decades before a reasonably natural generic classification within the Lecideaceae s. lat. is achieved. The enormity of the task can be appreciated from the fact that Zahlbruckner (1921-40) accepted no less than 1450 species in the genus Lecidea alone! In addition to the high number of taxa involved , further problems arise from the locating and obtaining on loan suitable (including type) material, and the many difficulties in observing and interpreting many microscopical, morphological, and ontogenetic features.
20 BRIAN JOHN COPPINS Micarea The genus Micarea was first validly described in 1825 by Elias Fries in his Systerna orbis vegetabilis (see p. 96), and was placed in his 'Tribus Collemaceae' on account of its rather gelatinous thallus, although he noted that it had Lecidea-hke apothecia. The generic name was little used by most 19th century lichenologists, although it was accepted with the single species {M. prasina) by a few such as Korber (1855). Towards the end of that century, J. T. Hedlund submitted his doctoral thesis to the University of Uppsala. In this work (Hedlund, 1892) he adopted and emended the genus to include 20 species, and his circumscription of the genus is essentially the same as that accepted by Vezda & Wirth (1976) and myself, although many species have since been added. Hedlund's sagacious work was evidently too revolutionary for his time, and it did not achieve international recognition. It seems that Hedlund was disillusioned and had difficulties in finding a position. He turned to horticulture (especially dendrology) and then became an authority on Sorbus. Although Hedlund's obvious talents were not lost to botany, they were sadly lost to lichenology, especially the study of microlichens. Vezda & Wirth (1976) slightly expanded Hedlund's concept of Micarea by including Lecidea sylvicola and related species (all without 'micareoid' algae), and also Bacidia beckhausii. Apart from the exclusion of B. beckhausii, my own concepts are much the same, although I have emended the genus very slightly so as to include species such as Lecidea (Helocarpon) crassipes and Catillaria intrusa. The first species of Micarea to be described was Lecidea [Micarea] lignaria Ach. (1808). By 1850 only seven of the currently accepted 45 European species were validly published. At about this time lichenologists began to make use of better quality microscopes and the additional characters they revealed. By the end of the nineteenth century 34 of the accepted species had been described. The European Micarea flora was increased by only one species (Lecidea subviolascens) between 1900 and 1960. In 1961 Vezda published Bacidia [Micarea] subleprosula, and as a result of the present studies (some in collaboration with Mr P. W. James, Dr A. Vezda, and Dr V. Wirth) a further nine species have been described. In the future a few additional species will probably be added to the European flora, but the greatest expansion within the genus will come from the study of extra-European collections; indeed, many European, undescribed, and described (in other genera) species are already known to me from parts of the world outside Europe. Materials During the course of this study I have examined about 3,000 specimens (c. 1800 from the British Isles) attributable to Micarea, plus a further c. 500 specimens which have been referred to other genera. Material has been received on loan from (or studied in) the following institutional herbaria: ABD, ANGUC, BEL, BERN, BG, BM, BON, C, DBN, DEE, DUKE, E, G, GLAM, GZU, H, HAMU, HBG, HEX, IMI, K (now in BM; cited as BM ex K), L, LD, LIV, LSR, M, MANCH, NMW, NWH, O, S, STD, STU, SUN, TUR, U, UPS, VER, WCR, WIS, WRSL; abbreviations according to Holmgren et al. (1981). In addition, numerous specimens have been received on loan from private herbaria. From the British Isles these are: Dr H. J. M. Bowen (Oxford), Dr R. W. M. Corner (Penrith), Mr I. P. Day (Carlisle), Dr U. K. Duncan (Arbroath; lichen herbarium recently gifted to E), Dr A. Fletcher (Leicester), Mr V. J. Giavarini (Parkstone, Dorset), Dr O. L. Gilbert (Sheffield), Mr R. Gomm (Taunton), Rev. G. G. Graham (Hunwick, Co. Durham), Mr A. Henderson (Leeds), Dr C. J. B. Hitch (Saxmundham, Suffolk), Dr P. D. Hulme (Aberdeen), Dr A. R. Pentecost (Royal Tunbridge Wells), Dr F. Rose (Liss, Hampshire; many specimens now in BM), Dr M. R. D. Seaward (Bradford), Mr J. F. Skinner (Southend-on-Sea), Dr P. B. Topham (Dundee), Mr R. G. Woods (Newbridge on Wye, Powys); and from elsewhere in Europe: Dr J. Hafellner, DrH. Mayrhofer, and Prof. Dr J. Poelt (all Graz, Austria), Mr L.-E. Muhr (Karlskoga, Sweden), Dr A. Vezda (Brno, Czechoslovakia), and Dr V. Wirth (Ludwigsburg, W. Germany). When studying a group of much misunderstood lichens it is a rewarding exercise to investigate folders of other superficially similar (but strictly unrelated) taxa, especially those that occur in
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Infrageneric considerations LICHEN
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5. Micarea bauschiana (Korber) V. W
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32. Micarea osloensis (Th. Fr.) Hed
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34. Micarea prasina Fr. LICHEN GENU
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conferanda (Lecidea) 205 confusula
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populina (Lecidea, Micarea) 31,32 p
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