Myriostigma miniatum (Lücking) Aptroot, Ertz, Grube & M. Cáceres 2015

Aptroot, André, Ertz, Damien, Silva, Jeanne Dos Reis, Grube, Martin & Cáceres, Marcela Eugenia Da Silva, 2015, The phylogenetic position of Coniarthonia and the transfer of Cryptothecia miniata to Myriostigma (Arthoniaceae, lichenized ascomycetes), Phytotaxa 218 (2), pp. 128-136 : 131-132

Myriostigma miniatum (Lücking) Aptroot, Ertz, Grube & M. Cáceres , comb. nov. ( Fig. 2 )

basionym: Cryptothecia miniata Lücking [as “Vain. ex Lücking”], in Lücking et al., Bulletin of the Florida Museum of Natural History, Biological Sciences 49: 140 (2011), Mycobank #811665

Type: — GUYANA. Vryheid Plantation, 14 February 1924, D.H. Linder 987 (holotype TUR-Vain 28367!).

Epitype: — BRAZIL. Sergipe: Poço Redondo, Serra da Guia ; alt. c. 800 m; on bark of tree; 26 January 2014, J.A. R. Silva T2 A29 (epitype ISE!; isoepitypes ABL!, BR!) .

Thallus spreading, covering an area of up to 5 cm diam., contiguous, mostly smooth but with occasional radial folds, dull, seemingly pruinose, pale greenish grey to whitish, c. 0.1 mm thick, IKI–, dull, surrounded by a c. 1–2 mm wide dark grey prothallus, photobiont trentepohlioid. Ascigerous zones delimited, round to irregular in outline, but mostly wavy linear, raised above the thallus and seemingly breaking through the thallus, 0.3–3 mm diam., up to 0.7 mm high, brightly orange, in section partly IKI+ pale blue. Asci almost superficial to shallowly to deeply immersed in the ascigerous zones, partly arranged above each other, hyaline but often surrounded by orange brown tissue, especially at the upper surface and then visible from above a black dots, globose, IKI–, with a dome-shaped extension in the endoascus, generally with 8 ascospores, 100–150 μm diam., wall c. 10 μm thick, in the apical part thickened to up to 18 μm thick. Ascospores densely muriform, ellipsoid, 53–91 × 28–42 μm, IKI–, ends broadly rounded, median lumina wider than lumina at the ends of the ascospore, but internal cell lumina not wider than those at the surface of the ascospore; with 14–17 transversal septa and 3–5 longitudinal septa in each transverse segment, not constricted at the septa; septation starting with several transversal septa in the median zone of the ascospore, septation proceeding towards the apices with simultaneous development of the longitudinal septa.

Secondary chemistry: —Thallus C–, K–, P–, UV –, ascigerous areas K+ purplish-violet, dissolving, later becoming blue-violet. TLC: 2- O -demethylperlatolic acid and orange pigment (probably skyrin).

Ecology and distribution: —On smooth bark of trees in primary middle to high altitude forests. Known from Costa Rica, Guyana and NE and SE Brazil.

Remarks: —The sequenced fertile specimen from Brazil is selected here as epitype, because the holotype is a century old and sterile. Lücking et al. (2011: 141) mention in the discussion under the species that they “specify an epitype from the Florida material” but they do not specify which one of the several specimens that is. In the description, TLC is said to have been performed on the “ paratype ”, which is equally not indicated.

The basionym is attributed here “Lücking” as sole author, not to “Vain. ex Lücking” as was done in Lücking et al. (2011: 140), because Vainio never used the name Cryptothecia miniata . Vainio called it (provisionally) Chiodecton miniatum .

We studied the same holotype specimen from the Vainio herbarium in Turku, but we were able to read and complete the collecting details with collector, number and date, all of which were cited by Lücking et al. (2011: 140) to be “not given”.

This species is impossible to mistake for any other known lichen, because of the striking contrast between the almost white thallus and the bright orange (not red: the epithet is misleading, meaning minimum red) ascigerous areas of very variable size that seem to break through the thallus in a way reminiscent of parasitic fungi. Internally it is similar to the type species of Myriostigma , M. candidum , which however also differs by the much smaller (45–65 × 15–25 μm) ascospores, by the much thinner foliicolous thallus and the more well-defined ascigerous areas which are overall more of similar size.

The orange pigment, an anthraquinone because of the K+ crimson reaction, was co-chromatographed with many other anthraquinone-containing tropical lichens. It was congruent in colour and Rf with skyrin, as present in a Cladonia species that was co-chromatographed on the same plate.

Additional specimens studied: — BRAZIL. Iporanga pr. Apiahy, IV. Puiggari 1179 (G) ; Ibidem, Puiggari 2788 (W, labelled as original collection of “ Arthothelium puiggarii A. Zahlbr. ”) ; COSTA RICA. Puntarenas: Valle de Coto Brus, S der Strasse nach San Vito , ca. 3, 5 km SE der Fährstation bei Paso Real, ca. 350 m, 9°N, 83°12’W ; Saum eines Sekundärwaldes ; 30. XII. 1978, J. Hafellner 7481 ( GZU) .

Figures

FIGURE 2. Myriostigma miniatum, isoepitype (ABL). A. habitus. B. detail showing ascomata. C. ascospore in median optical section showing large lumina in the center and small lumina in the periphery. D. the same ascospore in optical surface view showing only small lumina. Scale: A = 0.5 cm, B = 0.5 mm, C–D = 10 μm.