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Departamento Biología de Organismos, Universidad Simón Bolívar, Apartado 89000 Sartenejas, Baruta, Edo. Miranda, Venezuela
David L. Hawksworth
Departamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense, Plaza Ramón y Cajal, Ciudad Universitaria, ES-28404 Madrid, Spain
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONTAXONOMYKEY TO NORTH AMERICAN...LITERATURE CITED |
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Skyttea richardsonii sp. nov. is described from a sterile corticolous lichen in Maine. It is closest to S. tavaresae, the only other member of the genus to be reported as having annelations on the excipular hairs, but that species occurs on Loxospora spp. and differs in the K+ reaction of the exciple and ascospore size. Minute Phoma-like conidiomata found in some apothecia may represent an independent fungicolous fungus growing on the new species. This is the 10th species of the genus to have been discovered in North America; a key to these species is provided.
Key words: Ascomycota, discomycetes, lichenicolous fungi, lichens, Odontotremataceae
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONTAXONOMYKEY TO NORTH AMERICAN...LITERATURE CITED |
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). Seven species were included in the original account of the genus, and 20 have been added subsequently. However, Sherwood et al (1981) noted that S. thallophila (Karsten) Sherwood et al differed in important respects from the species they designated as type of the genus, S. nitschkei (Körb.) Sherwood et al, in having short hairs on the outside of the exciple. Zhuang (1988) found that such species could be better placed in Unguiculariopsis Rehm. Triebel (1989), considered Rhymbocarpus Zopf to be an earlier name for Skyttea, but Coppins et al (1991) pointed to differences in the ascus apices, the lack of excipular hairs and the almost perithecioid ascomata; a few species that had been placed in Skyttea nevertheless required transfer to Rhymbocarpus. Skyttea was revised in detail by Diederich and Etayo (2000) who accepted 17 species, and two species have been described since their monograph (Hafellner 2000, Etayo 2002). Here we describe a further new species collected in Maine, and only the second species in the genus to be discovered with annellated brownish excipular setae. In addition, we provide a key to the species so far recognized in North America to stimulate the interest of mycologists in the region in these minute but much-overlooked and fascinating discomycetes.
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TAXONOMY |
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Ascomata apothecioid, lichenicolous, immersed in the soralia of the host at first but becoming erumpent with maturity, 100–220 µm diam, deep urceolate with a central opening, pore 18.5–43.0 µm diam; receptacle greenish brown when fresh, dark brown to black when dry, with an incurved whitish margin surrounded by a fringe of hairs. Ectal exciplum textura angularis to globulosa, layer 18–20 µm wide, composed of thick-walled melanized greenish dark brown cells, K+ bright olive-green (not aeruginose green), fading to dark brown, cells 6–9.5 x 3–4.5 µm diam, walls 0.5–1.5 µm thick. Marginal hairs of two kinds, external hairs closest to the outside, and internal hairs closest to the centrum: external hairs cylindrical, wider at the base, and with a rounded or slightly tapering apex, percurrently proliferating, leaving often numerous annellations on the cell wall clearly seen in 2% KOH, not readily evident in lactophenol-cotton blue or Melzer’s reagent; cell walls uneven in thickness, thickening and then thinning at intervals, when mounted in Melzer’s reagent and suggesting irregular cyclical growth in the cell wall; hair length 16.5–35 µm, width 3.5–6 µm (base), 2.5–4 µm (middle), or 2–3 µm (apex), walls brown, irregularly thickened, to 1.5 µm wide; internal hairs cylindrical, round or pointed at the apex, widening at the base, septate, composed of 3–5 cells, wall thin and smooth, hyaline, hair length 25–35 µm, width ca 3 µm (base) to ca 2.5 µm (apex), wall 0.5 µm thick. Medullary excipulum and subhymenium indistinguishable. Hymenium 50–56 µm tall. Asci broadly cylindrical to elongate-clavate, lacking a well-defined stalk, 37–57.5 x 4.5–6.5(–11) µm, unitunicate, thick-walled, with a prominent apical cap 4–7 µm thick, lacking an apical pore but sometimes with a short internal apical beak, I- (Melzer’s reagent) treated directly and after pre-treatment in KOH, generally 8-spored, but some spores may be small and abort. Ascospores hyaline, ellipsoid, smooth, nonseptate, biguttulate, 1–2 seriate, 6–8 x 2–4.5 µm, length:breadth ratio 1.7–2.7. Paraphyses long, simple, filiform, septate, 1–1.25 µm wide in the middle, slightly enlarged at the apex to ca 2 µm diam. Conidiomata unknown (but see Observations below).
HOLOTY PUS: USA: MAINE: Washington County: Machiasport, Yoho Point, 44°37.5'N and 67°43.9'W, on thallus and soredia of unidentified lichen on white birch (Betula papyrifera), 8 Jun 2002, Glenn Boyd (BPI 843355).
Etymology. – The specific epithet is chosen to honor Dr David H.S. Richardson, (St Mary’s University, Halifax, Nova Scotia), outstanding lichen physiologist and communicator, who has sent collections of lichenicolous fungi to DLH for study throughout the years, including this Skyttea material, collected during one of the lichen courses he teaches at the Humboldt Field Research Institute, Eagle Hill, Maine.
Host. –
The ascomata are dispersed on grayish areoles of a sterile crustose lichen and are concentrated in deeply pigmented, bright orange, coarse soredia arising in tuberculate to verruciform superficial soralia. The thallus was K+ faintly yellowish, C– and PD–. The specimen was too small to risk destroying part of it for more detailed microchemical tests. The tuberculate nature of the soralia recalls those of the European Pertusaria multipuncta (Turn.) Nyl. and the North American counterpart P. multipunctoides Dibben, which differs in medullary chemistry and is to be expected in the northeastern U.S.A. (Dibben 1980). However, the thallus of P. multipunctopides is K+ yellow turning to red-brown and PD+ yellow changing to orange-red due to fumarprotocetraric acid. We also wondered whether the species might be a sorediate Opegrapha sp.; some species in that genus have yellow or orange soredia, such as O. sorediifera P. James, which is known in North America (Tønsberg 1994), and is K– and PD– but with C+ pinkish red soralia. On balance we are inclined to think the host is a species of Pertusaria, in which the soredia have become orange due to the chemical interplay between the Skyttea and the chemical components of the host.
Distribution. – Known only from the type locality in Maine, U.S.A.
Observations. –
This new species is only the second in the genus to have been recognized as having annellations on the excipular hairs. These have been illustrated in S. tavaresae by Diederich and Etayo (2000), but that species has an exciple turning bright aeruginose green in K, larger ascospores, and was described from Pyrrhospora cf. quernea (Dickson) Körb. In Diederich’s and Etayo’s key, our species comes closest to S. buelliae Sherwood, D. Hawksw. & Coppins, so far known only from Europe. It was described from Amandinea punctata (Hoffm.) Coppins & Scheid., lacks the two types of excipular hairs, lacks annellations on the hairs it does have, has much smaller excipular cells (4–6 µm) and more broadly ellipsoidal ascospores (4–7 x 2.5–3.5 µm). The differences between S. richardsonii and other Skyttea species so far known from North America will be evident from the key presented below.
Minute Phoma-like conidiomata were found growing on the hymenium in some apothecia of the Skyttea (FIG. 9). These most likely represent an independent fungicolous fungus because no anamorphs have been found in any Skyttea species and they were not found growing independently on the lichen, as would be expected if they were an anamorph. Pycnidia were ca 50 µm diam, with an outer wall of textura globulosa composed of 1–2-cell layers of round or irregular cells 3.5–4.5 x 2.5–3–0 µm, with thick brown walls; the conidiogenous cells were elongate-ampulliform, and 3.5–5.0 x 1.0–4.0 µm, forming enteroblastic conidia which were elongate-ellipsoid to roundish, and 2.0 x 0.5–1.0 µm. The conidia are smaller than in any of the 14 lichenicolous species of Phoma currently recognized (Hawksworth and Cole 2004), but in view of the scant material we do not describe this fungus further here. The species, however, should be sought when additional collections of the new Skyttea are made.
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KEY TO NORTH AMERICAN SKYTTEA SPECIES |
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Corresponding author. E-mail: myconova{at}terra.es
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LITERATURE CITED |
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Dibben MJ. 1980. The chemosystematics of the lichen genus Pertusaria in North America north of Mexico. Publ Biol Geol Milwaukee Public Mus 5:1–162.
Diederich P, Etayo J. 2000. A synopsis of the genera Skyttea, Llimoniella and Rhymbocarpus (lichenicolous Ascomycota, Leotiales). Lichenologist 32:423–485.
Etayo J. 2002. Aporación al conocimiento de los hongos liquenícolas de Colombia. Bibl Lich 84:1–154.
Hafellner J. 2000. Zur Biodiversität lichenisierter und lichenicoler Pilze in Eisenerzer Alpen. Mitt Naturw Ver Steiermark 130:71–106.
Hawksworth DL, Cole MS. 2004. Phoma fuliginosa sp. nov., from Caloplaca trachyphylla in Nebraska, with a key to the known lichenicolous species. Lichenologist 36:7–13.
Sherwood MA, Hawksworth DL, Coppins BJ. 1981 ("1980"). Skyttea, a new genus of odontotremoid lichenicolous fungi. Trans Br Mycol Soc 75:479–490.
Tønsberg T. 1994. Additions to the lichen flora of North America III. Halecania viridescens and Opegrapha sorediifera. Evansia 11:100–101.
Triebel D. 1989. Lecideicole Ascomyceten: Eine Revision der obligat lichenicolen Ascomyceten auf lecideoiden Flechten. Bibl Lich 35:1–278.
Zhuang W-Y. 1988. A monograph of the genus Unguiculariopsis (Leotiaceae, Encoelioideae). Mycotaxon 32:1–83.
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