Introduction
Since the monograph of Egea & Torrente (Reference Egea and Torrente1994) that included 24 species of Lecanographa, eight new taxa have been described in the genus: the lichens Lecanographa laingiana Diederich, Egea & Sipman from Papua New Guinea (Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1995), L. longicarpa Egea, Sérusiaux, Torrente & Wessels and L. tehleri Egea, Sérusiaux, Torrente & Wessels from Namibia (Egea et al. Reference Egea, Sérusiaux, Torrente and Wessels1997), L. littoralis Kantvilas from Australia and Tasmania, L. nothofagi Kantvilas from Tasmania (Kantvilas Reference Kantvilas2004), L. atropunctata Sparrius, Saipunkaew & Wolseley from Thailand (Sparrius et al. Reference Sparrius, Saipunkaew, Wolseley and Aptroot2006) and L. azurea Follmann from Chile (Follmann Reference Follmann2008), and the lichenicolous fungus L. imitans Werner & Follmann from the Galapagos Islands (Follmann & Werner Reference Follmann and Werner2003). In addition, Lecanactis elegans (Müll. Arg.) Stizenb. and Opegrapha rinodinae Vězda were newly combined in Lecanographa (Mies & Schultz Reference Mies and Schultz2004; Santesson et al. Reference Santesson, Moberg, Nordin, Tonsberg and Vitikainen2004). Lecanographa littoralis was recently chosen as the type species of the new genus Angiactis Aptroot & Sparrius (Aptroot et al. Reference Aptroot, Sparrius, LaGreca and Bungartz2008). A total of 33 species are currently accepted in the genus, but the recent discoveries suggest that more species will be described.
During a field trip by two of us (DE and JD) in Gabon in 2006, an interesting species of Lecanographa, characterized by 1-septate ascospores was collected. It proved out to be new for science and similar to a specimen collected in Guatemala by P. van den Boom in 2004. The new species is described here.
Material and Methods
Microscopical examination was carried out on hand-cut sections mounted in water, 5% KOH (K), or Lugol's reagent (1% I2) without (I) or with KOH pre-treatment (K/I). Measurements and drawings of asci and ascospores all refer to material examined in KOH. Drawings were prepared using a drawing tube. Ascospore measurements are recorded as (minimum–) 
−σX − 
+σX(–maximum), followed by the number of measurements (n); the length/breadth ratio of the ascospores is indicated as l/b and given in the same way. For the other characters, the minimum and the maximum values are given and are based on the examination of at least three different ascomata.
Thin-layer chromatography (TLC) of acetone extracts was performed on 20 × 20 cm silica gel 60 F254 layer glass plates using solvent systems C and G. For the visualization of the spots, 10% sulphuric acid was used as a reagent (Orange et al. Reference Orange, James and White2001).
The Species
Lecanographa uniseptata Ertz, van den Boom, Tehler & Degreef sp. nov
MycoBank No.: MB 515185
Thallus crustaceus, ecorticatus, albus vel pallide griseus. Ascomata rotundata vel lirellata, sessilia, atra, 0·2–1 × 0·2–0·6(–0·8) mm; discus expositus, pruina alba obtectus. Excipulum atrobrunneum, K+ olivaceum, infra clausum. Hymenium I+ rubrum. Paraphysoides ramosae anastomosantesque. Ascosporae fusiformes, 1-septatae, (12–)12·9–15(–16) × (2–)2–2·3(–2·5) μm. Conidia 3·5–4·5 × 1–1·5 μm.
Typus: Gabon, Ogooué-Ivindo Prov., Makokou, station de recherche d'Ipassa, parc entourant la station, 520 m, 0°30′N, 12°48′E, gros tronc dans un parc, 15 April 2006, D. Ertz 9859 (BR—holotypus; S—isotypus).
Fig. 1. Lecanographa uniseptata. A & B, thallus and apothecia (holotype); C & D, thallus and apothecia (van den Boom 33288). Scales: A = 1 mm; B & D = 0.5 mm; C = 2 mm.
Fig. 2. Lecanographa uniseptata (holotype), ascus, ascospores and conidia. Scale = 10 μm.
Thallus very thin, epiphloeodal, continuous or rimose, smooth, white or pale grey, matt, c. 40–80 μm thick. Photobiont Trentepohlia. Prothallus dark brown, 0·3–1 mm wide. Ascomata numerous, scattered more or less evenly over the thallus, more rarely in groups of 2–10, rounded, oblong or lirelliform, usually strongly lobate or with short branches, sessile, black, covered by a white pruina, small, 0·2–0·6(–0·8) mm diam. when round or up to 1 mm long when lirelliform; hymenial disc usually widely exposed, covered by a white pruina, with irregular crystals c. 2–5 μm diam. Excipulum dark brown to black, K+ olivaceous, very thick below the hymenium, extending slightly into the substratum, 12–35 μm wide laterally, 50–200 μm wide at the base. Hymenium hyaline or pale brownish, not inspersed with oil droplets, I+ red, 45–55 μm tall, K/I+ blue; subhymenium pale brown, K+ olivaceous, I+ red. Paraphysoids branched, especially in the epihymenium, anastomosing, 1–1·5 μm wide, not or slightly enlarged at the apex. Epihymenium hyaline to pale brown, I+ red, covered by a white pruina not dissolving in K (polarized light). Asci cylindrical-clavate, 8-spored, 40–50 × 7–8 μm, with a very small, hardly visible ocular chamber, without a K/I+ blue apical ring (Grumulosa-type). Ascospores fusiform, often slightly narrower in the lower half, hyaline, 1-septate, not constricted at the septum, (12–)12·9–15(–16)× (2–)2–2·3(–2·5) μm, l/b ratio 6·1–7·4 (n = 50); perispore c. 0·5 μm thick; brownish pigmentation not observed.
Pycnidia rare, visible as black dots, half-immersed, 60–120 μm diam.; wall dark brown, 5–10 μm thick, K+ slightly olivaceous. Conidia bacilliform, non-septate, 3·5–4·5 × 1–1·5 μm.
Chemistry. Thallus and apothecia K−, C−, KC−, PD−, UV− (white). TLC: traces of an unidentified fatty acid with relative Rf value C: 39, of a greyish brown spot after addition of sulphuric acid and heating with relative Rf value C/G: 45/71, and of two unidentified UV+ pigments (holotype tested).
Distribution and ecology. The species is known from Africa (Gabon; type locality) at 520 m altitude, growing on the bark of a large tree in a park surrounded by a dense tropical secondary forest. The Ipassa plateau regularly experiences whirlwinds coming up from the Ivindo valley. This phenomenon induces large clearings in the canopy and prevents the ageing of the forest. The resulting secondary vegetation is characterized by a dense lower layer comprising shrubs (mainly Rubiaceae and Euphorbiaceae) and herbaceous Zingiberaceae and Marantaceae. Most dominant trees at the Ipassa research station are Baphia leptobotrys and Scorodophloeus zenkeri (Leguminosae), Plagiostyles africana and Dichostemma glaucescens (Euphorbiaceae), Santiria trimera (Burseraceae), Greenwayodendron suaveolens (Annonaceae) and Pancovia pedicellaris (Sapindaceae) (Vande Weghe Reference Vande weghe2006). The new species is also known from Guatemala, growing on a trunk of Quercus sp. at 1325 m altitude. The Guatemala locality was occupied by a few ± scattered trees, Acer, Pinus and Quercus with a grassy understorey with a few rock outcrops. The only lichen species found on the outcrops was Paulia wrightii (Tuck.) Tretiach & Henssen. The only accompanying species identified on the Quercus tree, close to the Lecanographa were Cladonia ceratophylla (Sw.) Spreng., Parmeliella pannosa (Sw.) Müll. Arg. and Schismatomma sp. The present distribution suggests an unusual disjunction between Central America and Central Africa. However, the known distribution of the new species will undoubtedly change with additional collecting in the tropics and the recognition this publication allows. Therefore, it would be too speculative to discuss this distribution here.
Notes. In the identification keys to genera of Arthoniales by Egea & Torrente (Reference Egea and Torrente1994) and Grube (Reference Grube1998), the new taxon keys out in the genus Lecanographa. The species fits wellin the genus Lecanographa on account of the pruinose, often rounded and oblongascomata with a widely exposed hymenial disc, the carbonized excipulum and the Grumulosa-type asci. In a forthcoming publication on the phylogeny of the Arthoniales using LSU and RPB2 sequences, it will be shown that the species is closely related to a group that includes Lecanographa lyncea, the generic type species (D. Ertz et al. unpublished data). It differs from all other species of Lecanographa by the 1-septate ascospores that are unique within the genus. In order to verify that the species has not been described in a different genus, we compared the new taxon with species of the closely related genus Opegrapha. A few Opegrapha species are known to produce 1-septate ascospores. Opegrapha devia (C. Knight & Mitt.) Nyl. and O. stellata C. Knight, two lichen-forming and corticolous species, differ by much longer lirellae (0·5–2 mm and 2–4 mm long, respectively), by a lack of an excipulum under the hymenium and by much wider ascospores (6–8 μm and 3–6 μm, respectively) (Hayward Reference Hayward1977; Galloway Reference Galloway1985; Kantvilas & James Reference Kantvilas and James1991; Kantvilas et al. Reference Kantvilas, McCarthy and Louwhoff1994). Opegrapha uniseptata Matzer differs by its lichenicolous habit (on foliicolous Strigula species), epruinose ascomata and wider ascospores (3–4 μm) (Matzer Reference Matzer1996). The relevant literature was also checked to ensure that no other epithet was available for the new species, especially amongst the lichens known to occur in Gabon and Guatemala.
Additional specimen examined: Guatemala: Alta Verapaz dept.: E of Coban, San Pedro Carcha, Balneario Las Islas, hill along and above cascades, with Acer, Pinus and Quercus trees and some outcrops, 1325 m, 15°28.0′N, 90°18.5′W, on Quercus, 2004, P. & B. van den Boom 33288 (hb. P. van den Boom).
The authors are grateful to Cyrille Gerstmans and Omer Van de Kerckhove for technical assistance. The collection permits were granted by the CENAREST/IRET and the Herbier National (Gabon). Finally, the authors acknowledge financial support from the Fonds National de la Recherche Scientifique, Belgium (FNRS) / FRFC number 2.4515.06.
