Rhizoplaca adpressa Y. Y. Zhang & Li S. Wang, 2024

Zhang, Yanyun, Yin, Yujiao, Wang, Lun, Printzen, Christian, Wang, Lisong & Wang, Xinyu, 2024, Two new species of Rhizoplaca (Lecanoraceae) from Southwest China, MycoKeys 101, pp. 233-248 : 233

Rhizoplaca adpressa Y. Y. Zhang & Li S. Wang sp. nov.

Fig. 2

Type.

China. Yunnan Prov.: Kunming Ci., Shilin Co., 24°41′N, 103°22′E, 1883 m, on calcareous rock, 25 October 2017, Li S. Wang et al. 17-56973 (KUN-L0066051) .

Diagnosis.

The species Rhizoplaca adpressa is characterized by its placodioid and closely adnate thallus, pale green and heavily pruinose upper surface, lower surface of marginal squamules with a white and narrow free margin, the absence of lower cortex, and the basally non-constricted apothecia with orange disc that turn reddish-brown at maturity.

Etymology.

The epithet refers to the thallus, which is closely adnate to the substratum.

Description.

Thallus placodioid, umbilicate at least when young, rosulate, 1-3.5 cm across, centrally areolate, areoles continuous, plane, ca. 0.5 mm in diam., marginally squamulose, squamules radiating, 1-2.5 mm across. Upper surface pale green, heavily pruinose, smooth, rarely cracked, matt, lower surface with a white and narrow (ca. 1 mm) free margin, without tomentum. Upper cortex 13-20 μm thick, filled with pale brown (soluble in K) and brown (insoluble in K) granules, consisting of thin-walled and short-celled hyphae, 1.5-2.5 μm in diam., length of cell 3-7 μm, epinecral 10-16 μm thick, filled with brown granules, partly soluble in K, algal layer continuous, filled with black substance, insoluble in K, 67-75 μm thick, algae 8.5-12 μm in diam., medulla filled with black substance, insoluble in K, lower cortex lacking.

Apothecia common, laminal, scattered to slightly grouped, lecanorine, originally at same level with thallus, without thalline margin, then adnate, not constricted at base, 0.5-1 mm in diam. Apothecial disc orange, reddish-brown with age, pruinose, plane to slightly convex, thalline margin entire, thinner than 0.1 mm, concolorous with thallus. Hymenium filled with orangish and gray granules, insoluble in K, 58-70 μm high, epihymenium non-gelatinized, filled with brown (soluble in K) and orange granules (insoluble in K), weakly interspersed, 12-16 μm thick, parathecium extremely reduced, subhymenium with orangish gray granules, insoluble in K, 12.5-20 μm, hypothecium colorless, with orange and brown granules, insoluble in K, 50-180 μm, algae under hypothecium not continuous, irregularly grouped, cortex of thalline margin same as upper cortex, even, ca. 25 μm thick, paraphyses simple, ca. 3 μm in diam., septate, length of cell 10-13 μm, asci clavate, 50-55 × 15-22 μm, ascospores broadly ellipsoid to subfusiformis, hyaline, 9.5-13 × 6.5-9 μm. Pycnidia rare, conidia filiform, 16-25 × ca. 0.7 μm.

Chemistry.

K+ pale yellow, C-, P-; usnic and placodiolic acids were detected in TLC.

Distribution and ecology.

The new species only grows on exposed hard calcareous rock in karst landform at elevations of 1883-2623 m in Yunnan Province, China.

Notes.

Rhizoplaca callichroa is similar to this new species but differs in its yellowish green upper surface, the apothecia constricted at base when mature, and the persistently orange apothecial disc ( Zhang et al. 2020). Rhizoplaca huashanensis is similar to R. adpressa but differs in its black lower surface that contains a lower cortex, and its restricted distribution in Shaanxi (Northwest China) ( Wei 1984). Rhizoplaca chrysoleuca differs from R. adpressa in its larger apothecia (0.5-6 mm in diam.) and marginal lobes (2-5 mm long, 1-3 mm wide), a wide and bluish-black free margin on lower surface, the presence of gelatinized lower cortex, and the persistently orange apothecia with constricted base. Rhizoplaca phaedrophthalma also has reddish-brown apothecial disc when mature, but differs in the lobate thallus with yellowish and epruinose upper surface, the strongly convex disc, and the smaller ascospores, 7-10 × 4.5-7 μm ( Lü et al. 2020; Poelt 1958).

Additional specimens examined.

China. Yunnan Prov.: Dali, Heqing Co., Songgui Town , 26°18′N, 100°10′E, 2229 m, on calcareous rock, 20 June 2018, Li S. Wang et al. 18-58987 (KUN-L0065133), 18-58988 (KUN-L0065134), 18-59991 (KUN-L0065137), 18-58997 (KUN-L0065143), 18-59001 (KUN-L0065147), 18-59008 (KUN-L0065154), 18-59935 (KUN-L0063742), 18-59937 (KUN-L0063744), 18-59940 (KUN-L0063747), same location, 26°18′N, 100°10′E, 2260 m, on calcareous rock, 29 August 2005, Li S. Wang, D. L. Niu & H. Luo 05-25135 (KUN-L0040473); Kunming Ci., Shilin Co. , 24°41′N, 103°22′E, 1883 m, on calcareous rock, 25 October 2017, Li S. Wang et al. 17-56961 (KUN-L0066046), 17-56965 (KUN-L0062405), 17-67966 (KUN-L0062443), 17-56981 (KUN-L0076202), 17-57054 (KUN-L0062534), same location, 24°42′N, 103°21′E, 1890 m, on calcareous rock, 19 September 2003, Li S. Wang 03-22617 (KUN-L0040472), same location, 1910 m, on calcareous rock, 11 May 2008, Li S. Wang 08-29555 (KUN-L0040474), same location, 1900 m, on calcareous rock, 19 February 2010, Li S. Wang 10-31345 (KUN-L0048845); Lijiang Ci., Ning lang Co., Yongning Vil., 27°43′N, 100°40′E, 2675 m, on calcareous rock, 27 July 2020, Li S. Wang et al. 20-66488 (KUN-L0076274); Yulong Co. , Mt. Yulong , 26°56′N, 100°12′E, 2623 m, on calcareous rock, 31 December 2019, Li S. Wang & Y. Y. Zhang 19-66393 (KUN-L0076201) .

Figures

Figure 2. Rhizoplaca adpressa (KUN-L 0066051) A holotype B hyphae of upper cortex (LCB) C lower surface lacks lower cortex (LCB) D section of apothecia (LCB) E ascus (Lugol's solution) F ascospores (water). Scale bars: 10 μm (B); 20 μm (C); 50 μm (D); 5 μm (E, F).