Introduction
Recent detailed morphological and chemical studies have greatly improved the taxonomic knowledge of two large and widespread (especially in tropical areas) families of lichens, for example, the Graphidaceae (Staiger Reference Staiger2002) and the Thelotremataceae (Frisch Reference Frisch2006; Frisch & Kalb Reference Frisch and Kalb2006a). Several new genera have been described and old and disused generic names have been resurrected. However, molecular phylogenetic studies, based on parsimony analysis and Bayesian tree sampling of sequences of several genes support only in part the circumscription of many genera, and their relationships are poorly resolved (Staiger et al. Reference Staiger, Kalb and Grube2006; Mangold et al. Reference Mangold, Martín, Lücking and Lumbsch2008a). Furthermore, Mangold et al. (Reference Mangold, Martín, Lücking and Lumbsch2008a) found no support for the distinction of the two families, and thus reduced the Thelotremataceae into synonymy with the Graphidaceae. These molecular phylogenetic studies clearly demonstrate that many of the commonly used characters are homoplasic and either represent conservation of plesiomorphic characters in different clades, or parallel evolution. Nevertheless, several genera such as Acanthotrema, Chroodiscus, Glyphis, Phaeographis and Platygramme, are strongly supported by morphological and molecular studies.
The genus Topeliopsis was introduced by Kantvilas & Vĕzda (Reference Kantvilas and Vĕzda2000) to accommodate species of the Thelotremataceae with urceolate or almost perithecioid ascomata, a proper exciple fused with lateral paraphyses, and hyaline, non-halonate, large, muriform ascospores that turn reddish or purple in iodine (Mangold et al. Reference Mangold, Martín, Kalb, Lücking and Lumbsch2008b). As already highlighted by Kantvilas & Vĕzda (Reference Kantvilas and Vĕzda2000), the genus as delimited was heterogeneous, and was revisited by Kalb (Reference Kalb2001) and Frisch & Kalb (Reference Frisch and Kalb2006b). Their work found strong support in a maximum parsimony and bayesian analysis by Mangold et al. (Reference Mangold, Martín, Kalb, Lücking and Lumbsch2008b) and two genera can be distinguished: Topeliopsis Kantvilas & Vĕzda with 8 species (incl. T. azorica, see Coppins & Aptroot Reference Coppins and Aptroot2008) and Melanotopelia Lumbsch & Mangold with 2 species; T. meridensis being of uncertain position and possibly related to Chapsa.
During recent field studies, a further species of Melanotopelia was found in Rwanda and La Réunion. It differs from the other two species assigned to this genus and is described as new in this paper.
Materials and Methods
Morphological characters were studied on dry specimens using a dissecting microscope. Anatomical characters were measured under light and interference contrast microscopy on hand-cut sections and squash preparations mounted in water. An aqueous solution of KOH (10%) and lactophenol-cotton blue were used for detailed observation of asci and hamathecial elements. Amyloidy of the tholus of asci and hymenium was tested with Lugol's solution. The analysis of secondary metabolites was performed using TLC, with solvents C and G (Orange et al. Reference Orange, James and White2001); the reagent for the visualization of spots was sulphuric acid sprayed over the plates, followed by heating at 110°C for approximately 5 minutes.
The Species
Melanotopelia africana Sérus., M. Brand, Ertz, Eb. Fischer, Killmann & van den Boom sp. nov
Mycobank: MB512925
Differt ab M. rugosa ascomatis minoribus cum superficiei non 5-6-rugosi et poro terminale valde minore. Haec species M. toensbergii ex America boreo-occidentali in forma et magnitudine ascomatorum similis sed praesentiam acidi stictici et constictici et absentiam acidi protocetrarici valde differt.
Typus: Rwanda, Southern Province, Nyungwe National Park, Rwasenkoko swamp, along the road Butare-Cyangugu, S 02°31′29.4″ E 29°20′26.6″,c. 2350 m, pristine Erica thickets, on Erica johnstonii, 28 September 2006, E. Fischer & E. Sérusiaux (LG—holotypus; BG—isotypus).
(Fig. 1A, B & E)
Melanotopelia species, habitus. A & E, M. africana (holotype); B, M. africana (La Réunion, Forêt du Grand Matarum, 21 v 2008, M. Brand, E. Sérusiaux, P. van den Boom s . n., LG); C & F, M. rugosa (G. Kantvilas 444656, HO); D & G, M. toensbergii (isotype LG). Scales. A–D = 1 mm; E–G = 500 μm.
Thallus crustose, invading corticolous bryophytes or growing directly on bark, whitish grey to pale orange brown when dry, more vivid orange when moistened, not delimited, usually continuous. Photobiont a species of Trentepohlia with cells angular-rounded, 12–20 × 5–8 μm.
Ascomata sessile or slightly immersed in the substratum, usually single and not aggregated, subglobose or barrel-shaped, 0·4–0·5(–0·6) mm diam., 0·15–0·2(–0·25) mm high, at first black and closed and eventually opening through its apical, central ‘ostiole’ and finally with a terminal pore c. 50–100 μm wide and a pale brown, pinkish or almost greyish, irregular, slightly but distinctly swollen and denticulate margin, rarely slightly pruinose; disc hardly seen in mature stages through the pore, deeply and persistently urceolate. Excipulum 30–60 μm wide, cupular, opaque black-brown, K− and N−, with an internal layer of abundant, perpendicular short paraphyses, 10–20 μm thick. Hypothecium hyaline, 10–15 μm thick. Hymenium 100–200 μm thick, hyaline, without epihymenial zone. Paraphyses numerous, simple, c. 1·5 thick, not inflated at their apices. Asci subcylindrical (some becoming inflated when fully mature ascospores are still inside), of the Ostropales-type (thin-walled, with an easily distinguished tholus and a small ocular chamber, I−), 100–170 × 10–15 μm, (1–)2–spored. Ascospores ellipsoid, hyaline, muriform, I+ slightly reddish, not halonate, 130–160 × 30–45 μm when fully mature and ejected.
Conidiomata not found.
Chemistry. Stictic and constictic acids, and related compounds detected by TLC (all collections from Rwanda and one collection from La Réunion tested).
Ecology and distribution. Melanotopelia africana was first found in the Nyungwe Forest in Rwanda (now a National Park), one of the most species-rich montane forests in Africa (Ewango Reference Ewango2002; Fischer et al. Reference Fischer, Dhetchuvi and Ntaganda2003; Fischer & Killmann Reference Fischer and Killmann2008). Melantopelia africana has been found in two different localities and habitats in the Nyungwe Forest: a) on trunk of Erica, in pristine Erica johnstonii thickets and low forest with Hagenia abyssinica and Rapanea melanophloeios, in the Rwasenkoko swamp and b) just under the summit of Mt Bigugu, on Erica johnstonii and Podocarpus latifolius trunks in dense thickets of E. johnstonii, within a montane forest dominated by P. latifolius with Psychotria mahonii, Syzygium guineense and Apodytes dimidiata. In La Réunion, whose habitat diversity has recently been assessed by Strasberg et al. (Reference Strasberg, Rouget, Richardson, Baret, Dupont and Cowling2005), M. africana has been found in several different habitats: a) on isolated trees in a disturbed habitat by a picnic place, in the submontane windward forest zone, b) on a tree trunk (e. g. Nuxia verticillata) in the “Bois de couleurs des hauts” in the montane leeward forest zone, and c) on a trunk of Erica in “Avoune” wet, subalpine shrubland.
Notes. This species matches perfectly the description of Melanotopelia Lumbsch & Mangold (Mangold et al. Reference Mangold, Martín, Lücking and Lumbsch2008b), i.e. black perithecioid ascomata with a denticulate pore, inner part of the excipulum with numerous, perpendicular paraphyses, muriform, thin-walled ascospores reacting I+ slightly reddish. The previously described species are easily distinguished. Melanotopelia rugosa (Kantvilas & Vĕzda) Lumbsch & Mangold (fig. 1C & F) has larger ascomata (up to 0·8–1·0 mm wide), a much larger terminal pore and 5–6 longitudinal and white pruinose wrinkles over the ascomata surface (easily seen in young ascomata); a species known only from Australia/Tasmania (Kantvilas & Vĕzda Reference Kantvilas and Vĕzda2000). Melanotopelia toensbergii (Vĕzda & Kantvilas) Lumbsch & Mangold (fig. 1D & G), which has similar ascomata but produces protocetraric acid in its thallus versus substances in the stictic acid group for M. africana and M. rugosa; a species known from the coasts of Western North America (Kantvilas & Vĕzda Reference Kantvilas and Vĕzda2000; Breuss Reference Breuss2000).
During this study, material of Topeliopsis from many parts of the world has been examined. As a result, we suggest that Ramonia monospora Aptroot (described from Papua New Guinea and so far known only from the type collection, Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1997) represents a further species of the Topeliopsis muscigena group. Topeliopsis muscigena is here reported for the first time from La Réunion (present checklist available at www.biologie.uni-hamburg.de/checklists/lichens/africa/france_reunion_l.htm (visited on Jan. 2nd, 2009).
Specimens examined. Rwanda: same locality as the type, 31 iii 2005, D. Ertz, E. Fischer, D. Killmann, E. Sérusiaux s. n. (LG); ibid., 2007, D. Ertz 10950 & E. Fischer (BR); Nyungwe National Park, track to Mt Bigugu, under the summit, S 02°26′26.9″ E 29°15′0.92″, 2800 m, 20 ix 2006, dense thickets of Erica johnstonii on gentle slope, E. Fischer, A. Hambuckers, E. Sérusiaux s. n. (LG); ibid., 2007, D. Ertz 11070 & E. Fischer (BR).—La Réunion: Grand Etang (NE of Plaine-des-Palmistes), S 21°05.024′ E 55°39.115′, planted trees around the picnic area, 540–550 m, 29 v 2008, M. Brand, E. Sérusiaux, P. van den Boom s. n. (LG, REU); Cirque de Cilaos, Forêt du Grand Matarum, S 21°07.416′ E 55°28.983′, heavily disturbed montane forest (“Bois de couleur des hauts”), 1400–1450 m, 21 v 2008, M. Brand, E. Sérusiaux, P. van den Boom s. n. (LG); Forêt de Bébour, trail from main road, just N of Col de Bébour, to Cassé de Takamaka, 1340 m, 2008, P. van den Boom 40343 & 40355 (hb. van den Boom); ibid., track from the “Gîte” to Caverne Dufour, S 21°05.102′ E 55°31.362′, low shrub with Erica arborescens and E. montana, with enormous carpets of pleurocarpous mosses and Sphagnum on the ground, 1900 m, 2 vi 2008, M. Brand, E. Sérusiaux, P. van den Boom s. n. (LG).
Specimens of other species examined. Melanotopelia toensbergii: USA: Washington: Olympic National Park, Lake Ozetten W of Ozette River, N 48°09′ W 124°40.5′, 10–15 m, on Thuja plicata in oldgrowth, coniferous forest, 1998, T. Tønsberg 25545 (LG—isotypus).
Melanotopelia rugosa. Australia: Tasmania: The Sentinels, c. 2 km S of old Pedder Track rest area, S 42°53′ E 146°12′, 800 m, in moist, very sheltered rock crevices, on soil and peat, 1991, G. Kantvilas 444656 (HO).
Topeliopsis muscigena. La Réunion: Forêt de Bébour, track from the “Gîte” to Caverne Dufour, S 21°04.686′ E 55°31.535′, 2030 m, low shrub with Erica arborescens, E. montana and Phylica nitida with large open wet places, 1 vi 2008, M. Brand, E. Sérusiaux, P. van den Boom s. n. (LG).
Key for Melanotopelia species
1 Ascomata 0·6–1·0 mm diam., with a wide ostiole (0·1–0·3 mm) when mature; ascomata surface with 5–6 longitudinal wrinkles which are conspicuously white pruinose when young; thallus producing substances in the stictic acid group; Tasmania ... M. rugosa
Ascomata smaller, rarely exceeding 0·5 mm diam., with a punctiform ostiole (50–100 μm diam.); ascomata without pronounced wrinkles or white pruina ... 2
2(1) Thallus producing substances in the stictic acid group; Africa (Rwanda and La Réunion) ... M. africana
Thallus producing protocetraric acid; Western North America ... M. toensbergii
We thank the Institut de Recherche Scientifique et Technologique (IRST) in Butare, the Projet de Conservation de la Forêt de Nyungwe (PCFN) and the Bureau de Jumelage Rhénanie-Palatinat–Rwanda for logistical support during field trips in Rwanda. We are grateful to the Rwanda Office for Tourism and National Parks (ORTPN) for collection and export permits, and especially for their guidance and support in the Park of Nyungwe. We also thank our friends Mr Bonny Dumbo (République Démocratique du Congo) and Dr Alain Hambuckers (University of Liège) for their companionship and support during field work in Rwanda. Our field trip in La Réunion was made possible by a collection permit provided by the Parc National de la Réunion, through the courtesy of Mr B. Lequette; we also benefited from help by Mr J. M. Pausé (Parc National), Dr Cl. Ah-Peng and Prof. D. Strasberg of the Université of La Réunion in Saint-Denis; we thank them all very warmly. We also thank our colleagues and friends, Drs A. Aptroot, K. Kalb, G. Kantvilas (HO) and T. Tønsberg (BG) for the loan or gift of most valuable collections and for interesting suggestions. Finally, we wish to thank very warmly both referees for their most valuable comments and suggestions.
