Halegrapha redonographoides Dantas, Lücking & M. Cáceres, 2017

Dantas, Jaciele De Oliveira, Alves, Elaine Santos, Lücking, Robert & Cáceres, Marcela Eugenia Da Silva, 2017, Three new species of Graphidaceae (lichenized Ascomycota) from the semi-arid region of northeast Brazil, Phytotaxa 331 (2), pp. 289-294 : 291-292

Halegrapha redonographoides Dantas, Lücking & M. Cáceres , sp. nov. Fig. 1D–H

Mycobank No.: MB 822330.

Diagnosis: Differing from Halegrapha mucronata in the ecorticate thallus, somewhat pseudostromatic ascomata with immersed lirellae, a completely carbonized excipulum, and small, submuriform ascospores.

Type: BRAZIL. SERGIPE: Poço Verde, Fazenda Santa Maria da Lage ; 10º44’37” S, 38º05’44” W, 390 m; isolated remnant of Caatinga vegetation, on tree bark; 28 January 2015, J. Dantas ( ISE 30804 A — holotype) .

Etymology: The epithet refers to the Redonographa -like appearance of this species.

Description: Thallus corticolous, epiperidermal, 3–5 cm diam., continuous; surface uneven-rough, cream-colored to beige, opaque; prothallus absent but thin black prothallus line sometimes formed when bordering other lichens. Thallus in section 100–200 μm thick, ecorticate, with irregular, disrupted photobiont layer immersed between large clusters of crystals. Photobiont Trentepohlia ; cells rounded to irregular in outline, in irregular groups, yellowish green, 8–11 × 6–9 μm. Ascomata lirelliform, flexuose, unbranched to rarely sparsely branched, immersed into thickened thallus parts resembling pseudostromata, with lateral thalline margin, 0.5–2 mm long, 0.15–0.25 mm wide, 0.15–0.2 mm high; disc concealed; labia distinct, entire, gray-black; thalline margin cream-colored. Excipulum entire, completely carbonized, 50–90 μm wide, black; laterally covered by algiferous thallus including clusters of crystals; hypothecium prosoplectenchymatous, 10–20 μm high, yellowish; hymenium 70–90 μm high, colourless, clear. Asci clavate, 60–70 × 10–12 μm. Ascospores 8 per ascus, broadly ellipsoid with rounded ends, submuriform with 3 transverse and 0–2 longitudinal septa per segment, the principal septa irregularly arrangted, 10–15 × 6–10 μm, 1.3–1.7 times as long as wide, brown, I+ purplish-red when mature. Chemistry. Norstictic acid (major), connorstictic acid (trace), thallus section with K+ yellow efflux forming red, needle-shaped crystals.

Distribution and ecology: Thus far only known from the states of Sergipe and Tocantins in northeast and central Brazil, growing on tree bark in Caatinga and vegetation transitional towards Cerrado.

Characterization and taxonomic relationships: This new species is placed in the genus Halegrapha due to its Graphis -like thallus (whitish, with large crystal clusters) and ascomata (thick, carbonized labia) combined with Phaeographis - type ascospores (brown, small, with rounded ends; see Lücking et al. 2011). Only two other species of Halegrapha produce norstictic acid, namely H. mucronata (Stirt.) Lücking and H. masoniana G. Weerakoon, Lücking & Lumbsch (Lücking et al. 2011, Weerakoon et al. 2014). Both have a corticate thallus and also differ by the erumpent to prominent lirellae and transversely septate, longer ascospores (35–45 μm in H. mucronata , 50–70 μm in H. masoniana ); H. mucronata differs further in the laterally carbonized excipulum and H. masoniana in the lirellae with thick lateral thalline margin and in the inspersed hymenium. Regularly submuriform ascospores are thus far not known in the genus, although some ascospores may become submuriform in H. chimaera Rivas Plata & Lücking , which otherwise differs in the erumpent to prominent lirellae with striate labia and in the stictic acid chemistry (Lücking et al. 2011). Halegrapha redonographoides resembles a species of Redonographa (hence the specific epithet) in the ecorticate thallus containing large quantities of norstictic acid and in the somewhat pseudostromatic ascomata ( Lücking et al. 2013), but differs in the corticolous habit and the brown ascospores.

Additional specimens seen. BRAZIL. TOCANTINS: Itaguatins ; 5˚44’58” S, 47˚32’24” W, 150 m ; Cerrado vegetation, on tree bark; 22 October 2016, M. Cáceres & A. Aptroot 28794 ( ISE, ABL) .

Figures

FIGURE 1. Graphis alba (A, ISE 38000, paratype; B–C, ISE 38003, holotype). A–B. Thallus with lirellae showing conspicuous white labia cover. C. Ascospore. Halegrapha redonographoides (holotype). D–F. Thallus with more or less pseudostromatic lirellae, the reddish portions indicating decomposing norstictic acid; G–H.Asci with ascospores.Thelotrema pachysporoides (I, ISE 38001, paratype; J–L, ISE 38002, holotype). I–K. Thallus with apothecia; L. Ascus with ascospores. Scale in A–B, D–F, I–H = 1 mm, in C, G–H, L = 10 μm.