Diorygma guizhouense Wei Wu & S. B. Fu 2025, sp. nov.

Diorygma guizhouense Wei Wu & S. B. Fu sp. nov. Fig. 2 Etymology. The specific epithet “ guizhouense ” refers to the location where the holotype was collected. Holotype. KUN-L 0093724 Description. Sexual morph: Thallus corticolous, crustose, thin, tightly attached to the substratum, pale grey to greenish grey, rough, dull, lacking isidia and soredia, prothallus absent. Apothecia lirelliform, scattered or aggregated, erumpent, simple or irregularly branched, curved, and either terminally rounded or acute, measuring 2–5 mm long and 0.2–0.4 mm wide. Disc narrow to slightly open, covered with a white pruina. Exciple uncarbonized, brown at apex, pale yellowish brown towards base. Epihymenium brown, 10–30 µm high. Hymenium hyaline, not inspersed, 150–210 μm high, I + weakly blue-violet. Paraphysis anastomosing, filiform, 1–2.5 µm wide. Hypothecium weakly yellowish brown, 15–45 µm high. Asci fusiform, 118–222 × 37–82 μm, I –. Ascospores 1 / ascus, hyaline, richly muriform, peripheral and central spore locules of ± equal size, ends with gelatinous caps, 24–32 × 5–12 locular, (104 –) 125–119 (– 214) × (30 –) 36–58 (– 77) μm (x ̄ = 152 × 47 μm, n = 20), I –. Asexual moprh: not observed. Chemistry. Thallus K + reddish brown, C –, KC + orange, P + yellow, TLC: stictic acid, salazinic acid, norstictic acid. Material examined. China, • Guizhou Province, Congjiang County, Yueliangshan Nature Reserve, 25°20'8.56"N, 108°36'19.23"E, 987 m elev., 24 Oct. 2023, Ze Yang & Bo Liu, Y 400 (holotype KUN-L 0093724). Notes. The new species Diorygma guizhouense is characterized by lirelliform apothecia, which are erumpent with a narrow to slightly open disc covered by a white pruina. The exciple is uncarbonized, the hymenium is hyaline, not inspersed, and reacts I + blue-violet. The ascospores, one per ascus, are hyaline, richly muriform, with peripheral and central spore locules of approximately equal size, containing 24–32 × 5–12 locular, measuring 125–179 × 36–58 μm, I –. Chemically, this species contains stictic, salazinic, and norstictic acids. Phylogenetic analysis based on combined LSU and mtSSU sequence data indicates that D. guizhouense is closely related to Diorygma tiantaiense (Fig. 1). A comparison with D. tiantaiense reveals a 0.97 % nucleotide difference in the LSU region (7 / 723 bp). Morphologically, D. guizhouense differs by having a narrowly open disc (vs. fully open) and chemically by having a hymenium that reacts I + blue-violet (vs. I –). According to the TLC result, the new species contains stictic and salazinic acids rather than only norstictic acid in D. tiantaiense (Cui et al. 2024). According to the taxonomic key provided by Feuerstein et al. (2014), D. guizhouense is morphologically similar to D. dandeliense, which was later synonymized to D. karnatakense (Ansil et al. 2023). However, D. guizhouense and D. karnatakense occupy distinct clades in the phylogenetic tree, supporting their separation at the species level. Chemotaxonomically, TLC analysis shows that D. guizhouense contains stictic, salazinic, and norstictic acids, whereas D. karnatakense lacks stictic acid, and the ascospores of D. guizhouense exhibit a negative iodine reaction (I –), in contrast to the I + violet reaction reported in related species (Ansil et al. 2023). The nucleotide comparison reveals clear differences between the two species: 4.28 % (31 / 725 bp) for LSU and 3.45 % (25 / 725 bp) for mtSSU.