Introduction
The lichen genus Syncesia was monographed by Tehler (Reference Tehler1996) who recognized 17 species, including two new to science. No further new species has been described since then. The genus is recognized by stromatoid ascomata with exposed, pruinose and/or tomentose discs, carbonized hypothecium, fusiform 3-septate ascospores and by usually producing protocetraric and roccellic acids. It is most diverse in tropical and subtropical regions of Latin America. Only two species occur in continental Africa, S. intercedens (Müll. Arg.) Tehler known only from the type collection in Tanzania and from a second specimen in southern Africa, and S. mollis (Müll. Arg.) Tehler known only from the type collection in Tanzania. Species of Syncesia usually grow on bark, but some are also found on rock. As part of on-going projects on the lichen mycota of Madagascar and Rwanda, two conspicuous and characteristic species of Syncesia have been collected in montane forests and are here described as new.
Madagascar is a large island situated in the Indian Ocean about 12–25·5° south of the equator, well-known for its extraordinary biodiversity (Goodman & Benstead Reference Goodman and Benstead2003). Its lichen mycota remains very poorly studied and only c. 250 lichen species have been reported from the island so far (see Aptroot Reference Aptroot2008 for an exhaustive list of relevant publications).
Rwanda is a small East African country situated about 1–2° south of the equator. Due to its diverse geomorphology and altitudinal range, it harbours a species-rich mosaic of montane rainforests, afroalpine vegetation, dry forests and savannas (Fischer & Hinkel Reference Fischer, Hinkel, Löber and Rickal1991; Reference Fischer and Hinkel1992; Fischer & Killmann Reference Fischer and Killmann2008). The lichen mycota includes 178 lichen species recorded so far (Killmann & Fischer Reference Killmann and Fischer2005; Bock et al. Reference Bock, Hauck and Fischer2007), but several new taxa have been described recently from that country suggesting a very rich and original mycota (Elix et al. Reference Elix, Fischer and Killmann2005; Sérusiaux et al. Reference Sérusiaux, Fischer and Killmann2006, Reference Archer, Elix, Fischer, Killmann and Sérusiaux2009; Fischer et al. Reference Fischer, Ertz, Killmann and Sérusiaux2007; Ertz et al. Reference Ertz, Lawrey, Sikaroodi, Patrick, Fischer, Killmann and Sérusiaux2008; Archer et al. Reference Archer, Elix, Fischer, Killmann and Sérusiaux2009).
Material and Methods
Microscopic examination was carried out using 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 were all made on material examined in KOH. Drawings were prepared using a drawing tube. Ascospore measurements are recorded as (minimum–) x−σX – x+σX(–maximum) with all values rounded to the nearest multiple of 0·5 μm, 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 other characters, the minimum and the maximum values are recorded and are based on the examination of at least three different ascomata.
Thin-layer chromatography (TLC) of acetone extracts was performed using solvent systems B, C and G on silica gel 60 F254 layer 20 × 20 cm glass plates; 10% sulphuric acid was used as a reagent for the visualization of the spots (Orange et al. Reference Orange, James and White2001).
The following specimens of related species were examined: Sagenidiopsis merrotsyi R.W. Rogers & Hafellner: Australia (S, isotype); S. undulatum (Fée) Egea, Tehler, Torrente & Sipman: Brazil, Estado São Paulo, Tehler 7953 (S); Sagenidium molle Stirt.: Australia, Tasmania, Kantvilas 652/84 (S); Syncesia glyphysoides (Fée) Tehler: USA, Florida, Ertz 9084 & 9104 (BR); S. mollis (Müll. Arg.) Tehler: Tanzania (G, lectotype).
The Species
Syncesia afromontana Ertz, Killmann, Sérus. & Eb. Fisch. sp. nov
Mycobank No.: MB 512924
Syncesia cum thallo byssoideo, disco 0·2–1·0 mm diam., excipulo textura intricata; hypothecio brunneo, hymenio hyalino 80–120 μm in iodo rubescenti. Ab omnibus speciebus generis Syncesiae ascosporis fusiformibus 7-septatis hyalinis (42–)46–52(–55) × (4–) 4·5–5·5(–5·5) μm valde differt.
Typus: Rwanda. Southern Province, Nyungwe National Park, Rwasenkoko swamp, 2335 m, 2° 31′S, 29° 20′E, 31 March 2005, Ertz 7893, Killmann, Sérusiaux & Fischer (BR—holotypus).
Syncesia species, morphology. A, C, E & F, S. afromontana (holotype); A, thallus and apothecia; C, ascospores in a broken ascus; E, section through apothecia in water; F, same section, viewed in polarized light. B & D, S. mollis (lectotype).; B, thallus and apothecia; D, ascospore. Scales: A & B = 1 mm; C & D = 10 μm; E & F = 0·2 mm.
Syncesia madagascariensis (holotype). A, thallus and apothecia; B, section through apothecia in water, viewed in polarized light; C, ascus; D, ascospores. Scales: A = 2 mm; B = 200 μm; C & D = 10 μm.
Thallus up to 10 cm diam., byssoid, matt, continuous, greyish or greyish green, water-repellent, 150–400 μm thick, ecorticate, with an algal layer of 35–55 μm in the upper part, hyphae 2–3(–4) μm diam., covered by small and numerous crystals dissolving in K. Photobiont Trentepohlia; cells 15–20 × 9–13 μm. Prothallus pale to dark brown, byssoid, (1–)2–4 mm wide.
Ascomata tomentose, sessile, not or slightly constricted at the base, solitary and rounded or more often slightly to strongly sinuate, 0·2–0·8(–1·0) mm diam. when young, usually in large numbers covering areas of 0·5–6 mm diam., or sometimes when mature a larger part of the thallus, thus forming stromatoid structures with discoid individual ascomata; margin white, 50–110 μm thick, not protruding above the disc; hymenial disc pale brown, flat, slightly white pruinose. Excipulum of textura intricata, pale brown above, dark brown below where it is indistinguishable from the hypothecium, I+ orange, K+ slightly olivaceous, 10–20 μm thick; hyphae 2–3 μm thick. Hypothecium dark brown to black, K+ olivaceous, very variable in thickness (20–170 μm). Hymenium hyaline, not inspersed with oil droplets, 80–120 μm; hymenial gel I+ orange reddish, K/I+ blue; epihymenium pale to dark brown, I+ orange reddish, covered by a dense layer of crystals; crystals irregular, c. 0·5–3 μm diam., dissolving in K. Paraphyses branched, especially in the epihymenium, anastomosing, 1·5–2 μm, apically slightly enlarged to 2–3 μm, and covered by dark brown granules. Asci clavate, 8-spored, 70–105 × 18–19 μm, K/I−, except for a distinct K/I+ blue apical ring surrounding a small ocular chamber. Ascospores curved, ± fusiform, (6–)7-septate, microcephalic, not constricted at septa, cells square or rectangular, (42–)46–52(–55) × (4–)4·5–5·5(–5·5) μm, l/b ratio 9–11 (n = 50), becoming evenly dark brown when very over-mature; perispore indistinct.
Pycnidia not observed.
Chemistry. Thallus and apothecia K−, C−, KC−, P+ orange, UV+ dark brown; TLC: protocetraric acid (major) and traces of roccellic acid (type collection and specimen Ertz 10961 & Fischer tested).
Distribution and ecology. Known only from the type locality in Rwanda where it is abundant on several trunks of Erica in pristine Erica johnstonii thickets and low forest with Hagenia abyssinica and Rapanea melanophloeios, in the Rwasenkoko swamp, at c. 2330 m alt. The Nyungwe Forest in Rwanda, now protected under National Park status, represents 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). Rwasenkoko is one of the lowermost Erica forests in Rwanda due to a night cold air-lake where temperatures sometimes go below 0°C (Killmann & Fischer Reference Killmann and Fischer2005). The lichen mycota harbours cosmopolitan species such as Menegazzia subsimilis (Bjerke et al. Reference Bjerke, Fischer and Killmann2007) or Hypogymnia physodes that are restricted to montane habitats in the tropics, or near endemics such as Melanotopelia africana (Sérusiaux et al. Reference Sérusiaux, Brand, Fischer, Killmann, van den Boom and Ertz2009). The last species is known only from Rwanda (Rwasenkoko, Mt. Bigugu) and the Indian Ocean island of La Réunion. We visited many localities in the three National Parks in Rwanda during several collecting trips, but we were not able to find this new, rather conspicuous and easily recognized species in other localities. It seems, therefore, to be a very rare species in Rwanda, and might be endemic to the Nyungwe Forest. As mentioned by Tehler (Reference Tehler1996), most species of Syncesia are rare and serious attention with regard to conservation aspects should be paid to the biotopes in which the genus occurs.
Discussion. The new species fits well in the genus Syncesia by the tomentose stromatoid structures with discoid individual ascomata, the black hypothecium and by the presence of protocetraric acid in the thallus. It is easily recognized by the 7-septate ascospores, as all currently described species of Syncesia have 3-septate ascospores (Tehler Reference Tehler1996). The recently described lichenized species Plectocarpon syncesioides Cáceres & Lücking is similar to Syncesia but was assigned to the genus Plectocarpon because of its entirely carbonized ascomata and more than 3-septate ascospores (Cáceres Reference Cáceres2007). Otherwise this genus is only known as lichenicolous (Ertz et al. Reference Ertz, Christnach, Wedin and Diederich2005). Despite the fact that it has more than 3-septate ascospores, Syncesia afromontana is much closer to Syncesia than Plectocarpon because its ascomata are only partially carbonized.
In addition to the 7-septate ascospores, the new species is also characterized by a byssoid thallus that is a rare character state in the genus being known only in S. mollis and S. leprobola Nyl. ex Tehler (only slightly byssoid in the latter). Syncesia mollis differs from the new species mainly by the 3-septate ascospores (three ascomata of the lectotype were examined, with more than 150 mature ascospores seen, all being 3-septate), by its white thallus, mostly solitary and slightly larger ascomata (Fig 1) and by a slightly different chemistry (presence of atranorin in addition to protocetraric and roccellic acids, according to Tehler Reference Tehler1996).
The stromatoid ascomata, the byssoid thallus, the chemistry and the 7-septate asco spores resemble the genus Dichosporidium Pat., but this genus differs by having perithecioid and epruinose ascocarps with more or less closed discs and hooked or biclavate ascospores (Thor Reference Thor1990). Within the Arthoniales, the genera Tania, Sagenidiopsis and Sagenidium are also characterized by a byssoid thallus, but they all have solitary, rarely aggregated ascomata (Henssen et al. Reference Henssen, Renner and Vobis1979; Rogers & Hafellner Reference Rogers and Hafellner1987; Egea et al. Reference Egea, Tehler, Torrente and Sipman1995).
Additional specimens examined. Rwanda: same locality and date as the type, Sérusiaux s. n. (LG); ibid., 2007, Ertz 10961 & Fischer (BR).
Syncesia madagascariensis Ertz, Killmann, Razafin., Sérus. & Eb. Fisch. sp. nov
Mycobank No.: MB 515020
Syncesia cum thallo crustaceo, excipulo textura intricata; hypothecio brunneo, hymenio hyalino 100–150 μm in iodo rubescenti. Ab omnibus speciebus generis Syncesiae ascosporis fusiformibus 5-septatis hyalinis (50–)57·5–68(–80) × (3·5–)4–4·5(–5·5) μm valde differt.
Typus: Madagascar, Ambalamanakana, Ankazomivady, S of Ambositra, 1704 m, 20° 46′S, 47° 10′E, 4 October 2008, Ertz 12966, Fischer, Killmann, Razafindrahaja &Sérusiaux (BR—holotypus; KOBL; TAN—isotypi).
(Fig. 2)
Thallus up to 15 cm diam., crustose, matt, continuous to rimose with a verrucose surface, sometimes almost minutely subsquamulose, creamy with a greenish tinge, water-repellent, c. 50–250 μm thick, ecorticate, homoiomerous, hyphae 2–3 μm diam., covered by small and numerous crystals dissolving in K. Photobiont Trentepohlia; cells 7–14 × 6–10 μm. Prothallus pale to dark brown, byssoid, 2–4(–5) mm wide.
Ascomata tomentose, sessile, not or slightly constricted at the base, first solitary and rounded, eventually becoming strongly sinuate, 0·6–1·0 mm diam. when young, then forming stromatoid structures of 1–4(–5) mm diam. with discoid individual ascomata when mature; margin of the same colour as the hymenial disc or sometimes white, c. 70–150 μm thick, not protruding above the disc; hymenial disc pale brown, flat, sometimes slightly white pruinose. Excipulum very reduced, of textura intricata, pale to dark brown above, usually dark brown below where it is indistinguishable from the hypothecium, K+ slightly olivaceous, 10–20 μm thick; hyphae 2–3 μm thick. Hypothecium dark brown to black, K+ olivaceous, very variable in thickness (25–90 μm). Hymenium hyaline, not inspersed with oil droplets, 100–150 μm; hymenial gel I+ orange reddish, K/I+ blue; epihymenium pale to dark brown, I+ persistently blue, covered by a dense layer of crystals; crystals irregular, c. 1–4 μm diam., dissolving in K. Paraphyses richly branched, sometimes anastomosing, 1–1·5 μm, apically slightly enlarged to 2–2·5 μm, and covered by dark brown granules. Asci clavate, 8-spored, 100–125 × 17–20 μm, K/I−, except for a distinct K/I+ blue apical ring surrounding a small ocular chamber and the endoascus that is K/I+ pale blue especially in the young asci. Ascospores slightly to strongly curved, ± fusiform, slightly attenuated at one end, (4–)5(–6)-septate, microcephalic, not constricted at septa, cells rectangular, (50–)57·5–68(–80) × (3·5–)4–4·5(–5·5) μm, l/b ratio 13–16·5 (n = 50), becoming evenly dark brown when very over-mature; perispore indistinct.
Pycnidia not observed.
Chemistry. Thallus and apothecia K−, C−, KC−, P+ orange to red, UV+ yellowish to pale orange; TLC: protocetraric acid and trace of a fatty acid of Rf 48 in solvent C (probably roccellic acid) (all specimens tested).
Distribution and ecology. Known only from the type locality in Madagascar where it was collected from several trunks in a montane forest dominated by Myrtaceae and Syzygium species. Ambalamanakana represents a mosaic of secondary forest, swamp forest and open swamps.
Discussion. The new species with its tomentose stromatoid structures with discoid individual ascomata, black hypothecium and production of protocetraric acid in the thallus fits well in the genus Syncesia. It is easily recognized by the 5-septate ascospores as all known species of Syncesia have 3-septate ascospores, with the exception of S. afromontana described above which differs from S. madagascariensis by having notably shorter and (6–)7-septate ascospores and a byssoid thallus. Amongst the Syncesia species having consistently 3-septate ascospores (Tehler Reference Tehler1996), the closest species seems to be S. glyphysoides (Fée) Tehler that also has long ascospores and an UV+ pale yellow thallus. However, according to the description of Tehler (Reference Tehler1996) and the examination of two specimens (Ertz 9084 & 9104, see Material & Methods), S. glyphysoides differs by its consistently 3-septate ascospores that are distinctly shorter (41–55 μm) than those in S. madagascariensis, a water-absorbent, creamy to white and smooth thallus, smaller synascomata (up to 2·5 mm diam.), shorter hymenium and asci (65–100 μm and 60–90 μm respectively), and by the presence of atranorin in addition to protocetraric and roccellic acids (chemistry of Ertz 9084 & 9104 not tested).
Additional specimens examined. Madagascar: same locality as the holotype, Ertz 12961, 12954, Fischer, Killmann, Razafindrahaja & Sérusiaux (BR).
We thank the curators of the herbaria S, BR and G for the loan of specimens, 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. Further, we would like to thank our friends Mr Bonny Dumbo (République Démocratique du Congo) and Dr Alain Hambuckers (University of Liège) for their great companionship and support during field work in Rwanda. We are indebted to the staff of the Parc Botanique et Zoologique de Tsimbazaza in Antananarivo for logistical support of our research. We would like to thank especially Prof. Dr Andriamilaison Haingoson, Dr Solo Rapanarivo and Elisette Rahelivololona for their continuous support and the Ministère des Eaux et Forêts for collection and export permits of scientific material.
