Pyxine retirugella Nyl., Ann. Sci. Nat.

Mongkolsuk, Pachara, Meesim, Sanya, Poengsungnoen, Vasun & Kalb, Klaus, 2012, The lichen family Physciaceae in Thailand-I. The genus Pyxine, Phytotaxa 59 (1), pp. 32-54 : 49-50

16. Pyxine retirugella Nyl., Ann. Sci. Nat. ; Bot., 4, 11: 240 (1859).

Holotype:—NOUKAHIVA. [ Marquesas Islands , Nuku Hiva] ad cortices, D. E. S. A. Jardin s. n.; (H-NYL 31789!)— Pyxine consocians Vain., The Philipp. Journ. Sci., C , 8: 109 (1913) . Holotype:— PHILIPPINES, Comiran Island, Sulu Sea , ad corticem arboris frondosae, September 1910, E. D. Merrill 7167 p.p. ( TUR-VAIN. 8706!) .

Thallus 2–5 cm wide, adnate, subdichotomously lobate. Lobes irregular, discrete to contiguous or imbricate, plane to weakly convex but often slightly concave towards the tips, 0.3–1.0 mm wide, subrotund at the apices. Upper surface whitish to pale greenish grey or yellow-grey, pruinose towards the lobe tips or epruinose; isidia absent. Pseudocyphellae marginal and laminal, irregular, linear or becoming reticulate. Polysidiangia laminal and marginal, scattered or clustered, nodular to subcylindrical, short, ± branched, pustulate, bursting apically to produce granular soredia. Medulla uniformly white or cream. Lower surface black in the centre, paler towards the margin; rhizines ± dense, furcate. Apothecia rare, obscurascens - type, 0.5–2.5 mm wide; disc grey-pruinose when immature. Internal stipe distinct, white to pale brown, K-, P-. Ascospores 17–22 × 6–9 µm. Pycnidia not seen.

Chemistry: Cortex K + yellow, C-, KC-, P + yellow, UV-; medulla K + yellow → red, C-, P + orange; containing atranorin (minor), chloroatranorin (minor), norstictic acid (major), testacein (minor), unknown terpenes (minor).

Distribution and habitat:—Occurs on bark, rarely on rocks, in hill evergreen, mangrove and mixed deciduous forests. Also in Africa, Australia, Asia, Christmas Island (Indian Ocean) and several Pacific islands.

Notes:—This lichen is characterized by the adnate thalli, polysidiangia, white or cream medulla, cortical atranorin and obscurascens - type apothecia with a white to pale brown internal stipe. Pyxine physciaeformis is morphologically similar, but it contains cortical lichexanthone and has physciaeformis - type apothecia. P. boonpragobiana is morphologically also very similar, but differs by a different suite of terpenes.

Material from Thailand examined:— Chiang Mai ; Sunku, on twig of an unidentified tree in hill evergreen forest, 1400 m, 18°48' N, 98°58' E, 19 January 1999, P. Mongkolsuk 014376 ( RAMK).— Loei ; Phu Luang Wildlife Sanctuary, Phu Ho Forest Ranger Station, on the bark of an unidentified tree in mixed deciduous forest, 569 m, 17°06'41'' N, 101°38'36'' E, 29 July 2009, S. Meesim & K. Buaruang MSPL 403 ( RAMK).— Trat ; Muang district, near Ban Nam Chieo, on Rhizophora apiculata in a ± disturbed mangrove forest, 3 m, 12°10'25'' N, 102°28'37'' E, 25 February 2011, K. Kalb (hb. Kalb 38858) .