A regional study of the genus Phyllopsora (Ramalinaceae) in Asia and Melanesia Author Kistenich, Sonja Author Bendiksby, Mika Author Vairappan, Charles S. Author Weerakoon, Gothamie Author Wijesundara, Siril Author Wolseley, Patricia A. Author Timdal, Einar text MycoKeys 2019 53 23 72 http://dx.doi.org/10.3897/mycokeys.53.33425 journal article http://dx.doi.org/10.3897/mycokeys.53.33425 1314-4049-53-23 Phyllopsora siamensis Kistenich & Timdal sp. nov. Fig. 10B Diagnosis. Differs from P. imshaugii in having more well developed squamules, larger ascospores, and in substitutions in the mtSSU and ITS sequences. Type. THAILAND, Lampang : Doi Khun Tan National Park, loc. T118, 18°25'N , 99°14'E , 1000 m alt., hill evergreen forest, 1993-01-11, P.A. Wolseley & K. Boonpragob 3245 (BM 749856!-holotype) [TLC: norstictic acid; DNA MK412410 (mtSSU), MK412477 (ITS)]. Description. Thallus effuse, crustose to squamulose; squamules small, up to 0.4 mm wide, adnate, isodiametrical, more or less scattered when young, later contiguous or fusing, more or less crenulate, plane to weakly convex; upper side medium green, somewhat shiny, epruinose, glabrous; margin concolorous with upper side, often pubescent; isidia common, attached marginally to the squamules, cylindrical, simple or slightly branched, up to 0.15 mm wide and 1.5 mm long; upper cortex formed by thick-walled hyphae with rounded lumina (type 2), 15-30 µm thick, containing a few scattered crystals dissolving in K; medulla containing crystals dissolving in K and recrystallizing by forming acicular, red crystals, PD+ yellow, K+ red; prothallus well developed, thick, white. Apothecia seen in the holotype only, up to 1.5 mm diam., more or less plane when young, soon becoming weakly to moderately convex, medium brown, rounded to irregular, simple, when young with a rather thick, paler, weakly pubescent margin, later becoming more or less immarginate; excipulum pale brown in the rim, darker brown in inner part; hypothecium dark brown, K- ; crystals present in inner part of exciple and in hypothecium, dissolving in K and recrystallizing by forming acicular, red crystals; epithecium pale brown to colourless, K- ; ascospores narrowly ellipsoid or fusiform to bacilliform, simple, 15-22 x 3.5-4.5 µm (n=20). Conidiomata not seen. Chemistry. Norstictic acid (major), atranorin (minor to trace or absent). Medulla PD+ yellow, K+ red, C- , KC- . Distribution. Thailand. Etymology. The specific epithet refers to its occurrence in Thailand. Remarks. The species is morphologically and chemically very similar to P. imshaugii . Phyllopsora siamensis , however, may be distinguished by forming slightly larger squamules and longer ascospores (15-22 x 3.5-4.5 vs 10.5-14.5 x 3-4 µm ; the latter measurements are based on 40 spores in the type material from Jamaica) than P. imshaugii . So far, P. imshaugii is only known to occur in the Neotropics, while P. siamensis is solely known from Thailand. In the phylogenetic tree (Fig. 1), the four accessions of P. siamensis cluster in a strongly supported clade as sister to a clade comprising P. cinchonarum and P. concinna , from which the new species is readily distinguished by its chemistry. Phyllopsora imshaugii and P. siamensis are the only Phyllopsora species known to contain norstictic acid; the major compound of the two other species are lobaric acid and parvifoliellin, respectively. Additional specimens examined. THAILAND, Chiang Mai: Doi Suthep National Park headquarters walk, loc. 62.4, 18°48'N , 98°54'E , 1050 m alt., tropical mixed deciduous forest, on Lauraceae , 1993-03-27, B. Aguirre-Hudson & P.A. Wolseley 1643 (BM 749866) [DNA: MK412419 (mtSSU), MK412485 (ITS)]; Uthai Thani: Khao Nang Rum, Cathouse site, 15°29'N , 99°18'E , 650 m alt., tropical mixed deciduous forest, 1992-01-07, P.A. Wolseley & B. Aguirre-Hudson 5580 p.p. (BM 1031552 p.p.) [DNA: MK412423 (mtSSU), MK412487 (ITS)]; Khao Nang Rum, Khao Kiew, 15°27'N , 99°20'E , 1250 m alt., oak/chestnut forest, 1992-01-23, P.A. Wolseley and Onsar 5590 (BM 749833) [DNA: MK412418 (mtSSU), MK412484 (ITS)].