Plectocarpon parmotrematis Etayo, Flakus & Kukwa, 2018

Etayo, Javier, Flakus, Adam & Kukwa, Martin, 2018, Three new lichenicolous species of the genus Plectocarpon (Ascomycota: Lecanographaceae) discovered in the Bolivian Andes, Phytotaxa 357 (4), pp. 275-283 : 278-280

Plectocarpon parmotrematis Etayo, Flakus & Kukwa sp. nov. MycoBank MB 824896

Diagnosis: Differs from Celidium bacidiosporum in having smaller ascospores, an additional dark blackish pigment with a green tinge (K+ bluish green, not dissolving), and a different host selection ( Parmotrema reticulatum ).

Type:— BOLIVIA. DEPT. TARIJA: Prov. Burnet O’Connor, old road between Entre Ríos and Tarija, 21º25’50”S, 64º19’25”W, 2220 m, Boliviano-Tucumano forest with Podocarpus , on corticolous Parmotrema reticulatum , 1 Aug. 2015, J. Etayo 29426 (holotype LPB!, isotype herb. Etayo!). ( Fig. 2 )

Ascomata stromatic, developing on the upper surface of the host thallus, single or rarely 2–4- grouped, rounded or rarely ellipsoid, black, solitary, initially immersed and flattened, then bursting through the host cortex, with remnants of the host cortex often remaining over the ascomata, later superficial, convex, 0.4–0.8(–1) mm diam. Galls externally invisible, but fungus inducing overgrowths of host medulla and cause convex protuberance (seen on the lower side of the host thallus as a small cavity); surface of stroma cracked, with flat warts. Stroma multilocular, 130–200 μm thick; loculi 80–150 μm broad; sterile stromatic tissues well developed between the loculi, 15–40 μm wide in lower part and 75–100 μm wide in upper part, with two pigments, dominant one dark blackish with a green tinge, K+ bluish green (not dissolving), N+ violet then turning greyish brown (perhaps similar to pigment 4 according to Ertz et al. 2005), and the second one dark violet, K+ turquoise (dissolving and later forming small crystals), N+ reddish then turning brown (similar to pigment 5 according to Ertz et al. 2005), both pigments often mixed together and separate reactions of each therefore difficult to describe; base of the stroma 10–30 μm thick, with a brown pigment (K–), below with a 150– 180 μm thick white area corresponding to an abnormal growth of host medulla. Hymenium hyaline, I+ blue, turning quickly red, K/I+ blue, 75–100 μm high. Paraphyses septate, branched and anastomosing, 1.5–2.5 μm wide, regularly thickened near the septa and apically slightly enlarged up to 3–3.5 μm. Asci clavate, Opegrapha - type, wall apically thickened, with a K/I+ blue apical ring, 8-spored, 48–65 × 12–16 μm. Ascospores hyaline, smooth, bacilliform with obtuse ends, straight or slightly curved, not or slightly constricted at the septa, 3-septate, with cells more or less equal in length, each cell with 1(–2) large guttules, (15–)16–20(–23) × (3.5–)4–4.5(–5) μm (n=40), covered by a 1–1.5 μm thick gelatinous coat; granular perispore absent. Pycnidia immersed in Plectocarpon ascoma, with the same pigments as the stroma; conidiogenous cells 6–10 × 2–2.5 μm. Conidia bacilliform, colorless, 4–5 × 1–1.5 μm.

Host: The species inhabits the upper thallus surface (but not the soralia) of corticolous Parmotrema reticulatum s.l. [TLC: atranorin (minor), salazinic acid (major), consalazinic acid (minor)], and we assume it is as biotrophic mycoparasite because ascomata appear on healthy parts of the lichen thalli (not developing a necrosis). Some samples shared infections with still undescribed Clypeococcum and Pyrenidium species.

Distribution and habitat: The species is known from several localities in the Bolivian Andes where it grows in the Tucumano-Boliviano and Yungas humid montane forests.

Notes: Due to the pigments reacting K+ aeruginose to turquoise, Plectocarpon parmotrematis is most similar to Celidium bacidiosporum Steiner (1987: 231) reported on Parmotrema from Kenya and redescribed by Ertz et al. (2005). Only one ascoma of the latter species is known, which is similar to young ascomata of P. parmotrematis . Trying to figure out if P. parmotrematis is related to the material studied by Ertz et al. (2005), we sectioned young ascomata of the same size as in the syntype of C. bacidiosporum (0.5 mm in diam.). In such sections, loculi of P. parmotrematis are very similar to the figure in Ertz et al. (2005), however, in our species ascomata are at first almost simple and later divide into loculi with age. Both species have the similar dark violet pigment (K+ aeruginose-green, dissolving and later forming small crystals), and cylindrical ascospores with cells of a similar width. However, the following differences can be used to separate these two similar taxa. First, ascospores of C. bacidiosporum are much longer (22–34 μm) than those produced by P. parmotrematis (mostly 16–20 μm). Secondly, P. parmotrematis has two pigments (blackish with a green tinge and dark violet), while C. bacidiosporum has only the dark violet pigment. Finally, the small stroma of C. bacidiosporum sectioned by Ertz et al. (2005) contained mature asci and ascospores, but stromata of the same size in P. parmotrematis are practically immature, with only young asci, rarely containing few ascospores. This indicates that mature ascomata of P. parmotrematis are much larger than those of C. bacidiosporum . Additionally, asci found in C. bacidiosporum do not developed any amyloid structures in the apical part (reminiscent of the Arthonia -type), while the wall of those of P. parmotrematis are apically thickened and develop an evident K/I+ blue apical ring ( Opegrapha -type).

Both Plectocarpon parmotrematis and Celidium bacidiosporum can also be confused with P. violaceum Ertz, R. Sant., Diederich & Wedin in Ertz et al. (2005: 116) as these three species share similar stromatic pigments intensively reacting K+ aeruginose to turquoise ( Etayo & Sancho 2008). We consider that P. parmotrematis probably has the same two pigments as P. violaceum , but that the dark violet one (the pigment observed in C. bacidiosporum ) dominates. Notwithstanding P. violaceum grows on a different host ( Nephroma antarcticum ), has larger ascomata (0.3–3 mm in diam.) and asci (70–90 × 14–15.5 μm), and wider ascospores (5–7 μm) (Ertz et al. 2005).

Three other Plectocarpon species also inhabit members of the family Parmeliaceae (though not Parmotrema ): P. encausticum ( Nylander 1876: 238) Santesson (1993: 171) on Brodoa intestiniformis , P. hypogymniae Zhurb. & Diederich in Zhurbenko et al. (2008: 328) on Hypogymnia bitteri , and P. melanohaleae Christnach, Ertz & Diederich in Ertz et al. (2005: 71) on Melanohalea ushuaiensis . They all differ, besides different host species, in the presence of Atra-brown pigment (according to Meyer & Printzen 2000) in ascomata as well as some other morphological characters. Plectocarpon encausticum induces basally constricted galls with a thick margin of host thallus tissues. In P. hypogymniae , ascomata are larger (up to 2.5 mm in diam.) with a labyrinthiform or lirellate surface, asci are smaller, (35–)36–43 × (8–)9–12.5(–14) μm, and ascospores are shorter, (12–)13–15.5(–17) μm. Plectocarpon melanohaleae develops ascomata with a finely rough (or distinctly warted when older) surface, sterile stromatic tissues are poorly developed below and between the loculi, and ascospores are wider, 4.5–6 μm (Ertz et al. 2005; Zhurbenko et al. 2008). Recently, Plectocarpon diedertzianum Y. Joshi, Upadhyay & Chandra in Joshi et al. (2016: 258) has been described from India as a parasite of Parmotrema , however, the species differs clearly by its distinctly lirellaeform ascomata and the lack of K+ aeruginose pigment ( Joshi et al. 2016).

Additional specimens examined (paratypes). BOLIVIA. DEPT. CHUQUISACA: Prov. Belisario Boeto, between Nuevo Mundo and Villa Cerrano, 19º00’52”S, 64º20’17”W, 2569 m, Boliviano-Tucumano forest, on corticolous Parmotrema reticulatum , 16 July 2015, M. Kukwa 16322 ( LPB, UGDA); ibid. on Parmotrema sp. on branches, J. Etayo 2979, 29821, 29794 ( LPB, hb. Etayo). Prov. Zudañez, Área Natural de Manejo Integrado El Palmar, segunda villa de presto, Lomán, Salviatojo, 18º45’53”S, 64º49’57”W, 2875 m, Andino montano forest, on Parmotrema sp. on twiggs, 14 July 2015, J. Etayo 30375 ( LPB, hb. Etayo). DEPT. COCHABAMBA: Prov. Carrasco, Parque Nacional Carrasco, Sehuencas close to Monte Punku, 17º30’19”S, 65º16’40”W, 2222 m, lower montane Yungas cloud forest, on corticolous P. reticulatum , 27 Nov.2014, A. Flakus 25715, M. Kukwa 15085d ( KRAM, LPB). DEPT. TARIJA: Prov. Burnet O’Connor, near Entre Ríos, 21°25’32”S, 64°19’05”W, 2250 m, Tucumano-Boliviano altimontano forest with Alnus acuminata and Podocarpus sp. , on corticolous P. reticulatum , 9 Aug. 2012, J. Etayo 29367 (hb. Etayo, LPB); close to los Pinos, 21º25’30”S, 64º19’07”W, 2265 m, Boliviano-Tucumano forest, on corticolous P. reticulatum , 29 July 2015, M. Kukwa 16845, 16849a ( LPB, UGDA); ibidem, on corticolous P. reticulatum, J. Etayo 30619 ( LPB, hb. Etayo); ibid., close to los Pinos, 21º25’07”S, 64º18’50”W, 2190 m, Boliviano-Tucumano forest, on corticolous P. reticulatum , 29 July 2015, M. Kukwa 16856b ( LPB, UGDA); old road between Entre Ríos and Tarija, 21º25’50’’S, 64º19’25’’W, 2220 m, Boliviano-Tucumano forest with Podocarpus , on Parmotrema sp. on twig, 1 Aug. 2015, J. Etayo 30545 ( LPB); 60 km from Tarija, new road between Tarija and Entrerios, Boliviano-Tucumano forest with Podocarpus , 21º28’52”S, 64º17’41”W, 1837 m, on Parmotrema sp. on branches, 28 July 2015, J. Etayo 30666 ( LPB, hb. Etayo).

Syntype of Celidium bacidiosporum examined. [ KENYA]. OST AFRICA, Matchacos, on Parmelia pedicellata (i.e., Parmotrema andinum ; TLC: atranorin and lecanoric acid), 1896, Liechtenstern & Pospeschill s.n. (W-19376!).

Figures

FIGURE 2. Plectocarpon parmotrematis (holotype).A–B, habit of ascomata with a more or less smooth surface; C, cross section through multilocular stroma; D, cross section through part of stroma; E–F, asci showing amyloid zone above ocular chamber, seen as two dark blue lines (mounted in K/I); G, 3-septate, mature ascospores with a thick gelatinous coat. Scales: A=500 μm, B=250 μm, C=100 μm, D=50 μm, E–G=10 μm.