Bulletin of the British Museum (Natural History)

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LICHEN GENUS MICAREA IN EUROPE 87 most widely occurring compounds among lichen genera. It has been found in 11 Micarea species, although its presence in M. curvata has only been inferred from spot tests, the solitary specimen (holotype) being too small for t.l.c. analysis. In addition to these occurrences, gyrophoric acid is frequently detected in trace amounts in chromatograms of other taxa, especially M. prasina s. ampl. The fact that Micarea species often grow intermixed with other lichens, including several that contain gyrophoric acid (e.g. Lecidea icmalea and L. granulosa agg.) raises the question as to whether these trace amounts represent its presence as an accessory substance or as a contaminant. This is difficult to answer. Gyrophoric acid is certainly found in the M. prasina complex, as it has been detected in large amounts in the type material of Lecidea levicula Nyl. from Cuba. (Further studies are required to establish the taxonomic status of L. levicula.) Well-developed specimens of M. denigrata, M. nitschkeana, and M. melaena have an areolate thallus containing readily detectable quantities of gyrophoric acid. However, the thallus of these species is sometimes scurfy-granular and blackish due to disruption by invading dematiaceous fungi and non-lichenized algae, and gyrophoric acid is produced in very low amounts or is apparently absent altogether (not detectable by t.l.c). The most surprising result of the chemical studies in Micarea was the discovery of three unknown, but very distinctive, compounds in M. prasina. The three compounds can be characterised thus (UV at 254 m/x): prasina unknown A. TDA 5: HEF 6, UV-h blue-white. After H2SO4 and charring: UV+ dull orange-red, dull orange in daylight. prasina unknown B. TDA 5: HEF 6, UV+ blue (less bright than 'unknown A'). After H2SO4 and charring: UV-f- vivid citrine-yellow, yellow (without orange tinge) in daylight. prasina unknown C. TDA 4-5: HEF 6-7 (slightly higher than 'unknowns A and B'), UV-I- grey or pale mauve (TDA) or ± colourless (HEF). After H2SO4 and charring: UV-I- violet-blue, ± colourless in daylight but turning a pale pinkish-lilac after several weeks. In all the numerous European and North American specimens of M. prasina s. ampl. examined so far, these compounds have never been found in combination, and M. prasina exists as three distinctive chemical races (see taxonomic account of M. prasina for further discussion). None of the three compounds can be identified in the tabulations of Culberson (1972), and they have never been encountered in other genera during the numerous and diverse investigations by Mr P. W. James (pers. comm.). Samples of specimens containing 'unknowns A and B' are currently being studied by Dr J. A. Elix. The identification of hchen substances (even if only by spot tests) is essential for distinguishing sterile specimens of M. leprosula from M. subleprosula, and for separating the two varieties of M. lignaria; it is also of great value in the routine identification of many other species (see 'Keys to species'). The three European races of M. prasina are not distinguishable by spot tests, but are readily identified by t.l.c. Pigments The nature of pigments and their location (especially within apothecia) are of prime importance in the delimitation of species within many lichen genera, particularly those included in the Lecideaceae, and Micarea is no exception. Little is known of these acetone insoluble pigments and a detailed knowledge of their structure and biogenesis would be invaluable for the evaluation of their taxonomic significance. On the basis of the colours seen in water mounts and the colour changes brought about by the application of a strong alkali (KOH) and a strong acid (HNO3) at least eight pigments can be recognized in Micarea. A very provisional summary of these pigments is given below: Pigment A. Green or aeruginose, K- or -I- green intensifying, HNO3+ red; in various tissues (according to species) of M. assimilata, M. bauschiana, M. cinerea, M. intrusa, M. lignaria, M. melaena, M. peliocarpa, M. sylvicola, and M. tuberculata. Pigment B. Purple, K+ green, HNO3+ purple-red; mostly in the hypothecium of M. assimilata, M. contexta, M. crassipes, M. eximia, M. melaena, M. nigella, and M. sylvicola (rare forms). Pigment C. Purple, K+ purple intensifying (sometimes partly dissolving into solution); occasionally in
. 88 BRIAN JOHN COPPINS the epithecium (M. melaenida and forms of M. crassipes and M. melaend) but mainly in the hypothecium {M. assimilata, M. crassipes, M. melaena, M. melaenida, and M. subviolascens) Pigment D. Olivaceous, K+ violet (also C+ violet), HNO3+ red; in various tissues (but rarely in the hypothecium, and then in low concentrations) of M. denigrata, M. elachista (mostly in pycnidia), M. globulosella, M. hedlundii, M. melanobola, M. misella, M. nitschkeana, M. prasina, M. subviolascens, and M. synotheoides Pigment E. Fuscous brown, K+ dissolving into solution, HNO3—; in the epithecia of M. elachista SiXxdM. rhabdogena. Pigment F. Brown (sometimes slightly tinged reddish), K- (not dissolving), HNO3- or + orangebrown; in various tissues (according to species) of A/, botryoides, M. curvata, M. incrassata, M. lutulata, M. muhrii, M. myriocarpa, M. osloensis, M. subnigrata, andM. turfosa. It is quite possible that more than one pigment is involved here. Pigment G. Dilute yellowish, K+ purple (oily droplets), HNO3- ; in goniocysts and sometimes the lower hymenium and hypothecium of M. hedlundii. Pigment H. Pale yellowish orange, K+ purple, HNO3— ; in cytoplasm of some ascogenous hyphae, asci, and spores of M. intrusa. This is possibly similar (or identical) to pigment G. Pigment complexes involving mixtures of pigments A, B, and C are often found (especially in the hypothecium) in M. assimilata, M. contexta, M. crassipes, M. melaena, M. subviolascens, and M. sylvicola; see the individual species accounts for further details. The existence of such complexes suggests that pigments A, B, and C are closely related chemically. Pigment A is probably identical to that found (usually in the epithecium) in a large number of lichens, especially in Led^efl 5. lat., Catillarias. lat., Bacidias. lat. and Lecanoras. lat. Pigment C is probably of rare occurrence outside Micarea, but I know of it in the epithecium of Bacidia beckhausii and in several species of Pertusaria (e.g. P. hymenea and P. oculata). I have not encountered pigment E in any other lichens, but it should be compared with the pigment(s) responsible for the ionomidotic reaction found in several genera of non-lichenized discomycetes (Korf , 1973). Pigment F is probably of wide occurrence, but there may be several pigments that impart a brown or 'melanized' appearance in tissues. The dark violet-blue, K-h aeruginose granules occasionally seen in the hymenium of M. contexta and M. lignaria (and also the apothecia of Lecidea hypnorum and Dactylospora lobariella), is probably related to (if not the same as) pigment B, and it may be the same as the epithecial pigment found in Bacidia absistens, Mycoblastus fucatus , and Schaereria tenebrosa. Ecology No detailed ecological studies have been made in connection with this primarily taxonomic study of Micarea, and much of the discussion given below is based on floristic notes and casual field observations. For most amateur and professional lichenologists alike, the species oi Micarea are little known, poorly understood, and much overlooked in the field. For this reason the following account is more of a guide to collectors, rather than an ecological dissertation. Additional ecological notes are also included in the taxonomic accounts of each of the Micarea species treated. Syntaxonomic nomenclature follows James ef a/. (1977). General habitats Micarea species occur in a wide range of habitats but are confined to substrata with a low pH (below c. pH 5) and generally avoid nutrient enriched situations. Thus, they are absent from limestone rocks, tops of bird-perching stones, seashores, and basic bark. There are a few partial exceptions, for example M. denigrata can occur on wooden fencing and other timber in farmyards, M. prasina can occur on soil and debris among rocks in the upper seashore, and M. lignaria has been found on exposed limestone growing over mats or cushions of moribund bryophytes from which free calcium ions have presumably been leached out. The bark of Acer and Ulmus normally has a pH which is too high for species of Micarea (with the exception of M. prasina in some situations), but in areas heavily polluted by sulphur dioxide and its derivatives (e.g. West Yorkshire Conurbation), bark pH can be substantially lowered (Gilbert, 1970), thus providing a suitable substratum for species such as M. melaena (q.v.) and M. botryoides (q.v.). .
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. 18 BRIAN JOHN COPPINS 11. M.denig
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20 BRIAN JOHN COPPINS Micarea The g
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22 BRIAN JOHN COPPINS Morphology Th
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24 BRIAN JOHN COPPINS (ii) Goniocys
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26 BRIAN JOHN COPPINS A B Fig. 2 'M
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28 BRIAN JOHN COPPINS 3 00
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30 BRIAN JOHN COPPINS Fig. 5 Sketch
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32 BRIAN JOHN COPPINS Fig. 6 Ascus
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34 BRIAN JOHN COPPINS Fig. 8 M. ala
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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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