Rhizoplaca pachyphylla (H. Magn.) Y. Y. Zhang, 2020

Zhang, Yan-Yun, Wang, Xin-Yu, Li, Li-Juan, Printzen, Christian, Timdal, Einar, Niu, Dong-Ling, Yin, An-Cheng, Wang, Shi-Qiong & Wang, Li-Song, 2020, Squamarina (lichenised fungi) species described from China belong to at least three unrelated genera, MycoKeys 66, pp. 135-157 : 135

Rhizoplaca pachyphylla (H. Magn.) Y. Y. Zhang comb. nov. Fig. 3E-H

Lecanora pachyphylla H. Magn., Lichens from Central Asia 1: 120-121 (1940) (Basionym) ≡ Squamarina pachyphylla (H. Magn.) J.C. Wei, Enumeration of Lichens in China: 232 (1991).Type: China, Gansu Province, 3800-3850 m elev., on rock, 1932, Birger Bohlin (S-Holotype!).

Description.

Thallus saxicolous, areolate without lobate margin, to 4 cm across, to 5 mm thick; areoles continuous, plane to slightly convex, 1-2 mm across; upper surface yellow, densely shallow rimose; lower side with thick, grey to white hypothallus. Upper cortex uneven, filled with yellowish-brown granules dissolving in KOH, 32-48 μm thick, algal layer continuous, variable in height, 80-128 μm; medulla very thick, filled with grey to pale brown granules; lower cortex lacking.

Apothecia common, usually densely grouped, irregular in shape, up to 5 mm in diam.; disc black, pruinose at the centre, plane when young, strongly concave with age; thalline margin thin and crenate, strongly bending towards inside with age; hymenium colourless, I+ blue, ca. 50 μm high; epihymenium containing yellowish-brown granules, ca. 9.5 μm high; subhymenium and hypothecium colourless; paraphyses evenly septate, simple, 2-3 μm in diam., apex more or less swollen and bluish-green, ca. 4.5 μm in diam.; ascus Lecanora -type, 8-spored; ascospores regular in shape, ellipsoid, colourless, 5.8-8 × 3-4.5 μm.

Chemistry.

Upper cortex K-, C-, P-, medulla K-, C-, P-; usnic acid and traces of unknown substances.

Ecology and distribution.

Growing on rock at elevations of 3291-3909 m. Only known from Gansu Prov., China.

Notes.

The holotype grows on rock with Lecidea tessellata Flörke, Lecanora asiatica H. Magn. and Xanthoria elegans (Link) Th. Fr. and contains numerous apothecia.

This species was originally described as a Lecanora by Magnusson (1940) and transferred to Squamarina by Wei (1991). It is characterised by the yellowish, areolate and very thick thallus, the black lecanorine apothecia and the very small ascospores. We transfer this species to Rhizoplaca , primarily based on the phylogenetic results (Fig. 4 ) and also based on the yellow thallus, the large, concave apothecia with margins bending towards the inside and the Lecanora -type ascus. Rhizoplaca pachyphylla is phylogenetically closely related to R. callichroa , R. chrysoleuca and R. huashanensis , but differs in the very thick and areolate thallus without lobate margin and the very small ascospores, 5.8-8 × 3-4.5 μm. Rhizoplaca subdiscrepans is similar to R. pachyphylla in the squamulose thallus, but differs in the orange apothecia, longer ascospores, 7-12 × 3.5-4.5 μm, and the presence of pseudoplacodiolic or placodiolic acids. Rhizoplaca melanophthalma (DC.) Leuckert is also similar to the species in having black apothecia, but differs in the umbilicate thallus and the larger ascospores, 6.5-12 × 4-7 μm.

Specimens examined (KUN-L).

China: Gansu Province: Shubei Co., Mengke Glacier, 3942 m elev., 39°12'N, 95°23'E, on rock, 2018, Li-Song Wang et al. 18-59446, 18-59466, 3785 m elev., on rock, 2018, Li-Song Wang et al. 18-59482; Yumen Ci., Yuerhong Vi., 3291 m elev., 39°50'N, 96°45'E, on rock, 2018, Li-Song Wang et al. 18-59560, 18-59561.

Figures

Figure 3. Rhizoplaca callichroa (A-D KUN-L 19 - 62900): A habit B apothecial anatomy (LCB) C ascus and spores (Lugol's) D section of pycnidia (LCB). R. pachyphylla (E-H KUN-L 18 - 59446): E habit F section of apothecia G ascus and spores (LCB) H section of thallus (LCB). Scale bars: 100 μm (B, F, H); 10 μm (C, G); 20 μm (D).

Figure 4. Maximum Likelihood phylogeny of the genus Rhizoplaca and related genera of Lecanoraceae, based on combined nrITS, nrLSU, RPB 1, RPB 2 and mtSSU. ML bootstrap value ≥ 70 % and posterior probabilities ≥ 0.95 from the Bayesian analysis are given adjacent to nodes.