Pleopsidium tumidulum M. Ai, Xin Y. Wang & Li S. Wang, 2025

Ai, Min, Miao, Cong Cong, Worthy, Fiona Ruth, Nurtai, Lazzat, Zhang, De Ning, Zhang, Sheng Bang, Han, Gui Lan, Wang, Li Song & Wang, Xin Yu, 2025, A new revision of the lichen genus Pleopsidium (Acarosporales, Acarosporaceae) in China reveals two new species, MycoKeys 120, pp. 255-276 : 255-276

Pleopsidium tumidulum M. Ai, Xin Y. Wang & Li S. Wang sp. nov.

Figs 6 , 7

Type.

China. • Qinghai Prov.: Dulan Co., Xiangjia Vil. , 36°12'19"N, 97°01'00"E, alt. ca 2850 m, on rock, 15 Sep. 2020, L. S. Wang et al. 20-67124 (holotype: KUN; isotype: SDNU) .

Diagnosis.

The new species differs from other Pleopsidium species by lacking fatty acids, having thick thalli, convex, plump, and swollen lobes, and by molecular data.

Description.

Thallus crustose, tightly attached to the substrate, areolate at center, radiate-plicate at margins; areoles approximately uniform, closely linked, fertile, 1.5–2.5 × 1.0– 1.8 mm; marginal lobes long, convex, and plump, 2.5–4.5 mm long, 0.8–2.5 mm wide, 1.5–3.0 mm thick, tightly attached to the substrate; the apices of marginal lobes have lower cortex; upper surface bright yellow with rhizocarpic acid in cortex, smooth, becoming convex when mature; upper cortex yellow, 25–37.5 μm thick; algal layer 62.5–100 μm thick; medulla white, more than 87.5 μm thick; areoles at the center without the lower cortex. Apothecia numerous, one apothecia in each areola, cryptolecanorine to lecanorine, roundish, 1.3–2.5 mm in diam.; disc yellow, darker than thallus, plane to slight convex; margins yellow, concolorous with thallus; epihymenium brownish yellow, 25–37.5 μm thick; hymenium hyaline, 100–112.5 μm high; paraphyses simple, with 4–5 septa, apices often expanded; hypothecium hyaline, 50–62.5 μm high; asci clavate, 37.5–55 × 17.5–25 μm, ± 100 - spored; ascospores hyaline, ellipsoidal, aseptate, 4–5 × 2–3 μm. Pycnidia immersed; conidia bacilliform, 2–3 × 1 μm.

Chemistry.

Thallus UV + dark orange-yellow, P –, K –, C –, KC –. Containing rhizocarpic acid and an unknown acid (trace).

Distribution and ecology.

This species usually grows on exposed rocks in the Gobi, desert steppe, and in bush formations at elevations between ca 1540 m and ca 3470 m. It is distributed in the Qinghai, Xinjiang, and Neimenggu provinces in China.

Etymology.

The epithet “ tumidulum ” refers to its plump and swollen lobes.

Note.

It is morphologically similar to Pleopsidium gobiense and P. corrugatulum , but P. tumidulum has thicker and smoother thalli (up to 3 mm thick), longer marginal lobes (up to 4.5 mm long), bigger apothecia (over 1.5 mm), and smaller ascospores (less than 5 μm long). The new species differs from clade 2 Pleopsidium species ( P. discurrens , P. chlorophanum , and P. flavum ) in lacking fatty acids.

Selected specimens examined.

China. • Neimenggu Prov.: Huhehaote Ci., Luotuogou Vil. , 42°56'22"N, 86°09'05"E, alt. 2680 m, 11 Aug. 2012, Lazzat Nurtai 20121958-1 ( XJU) ; • Alxa Youqi , 39°04'27"N, 101°01'10"E, alt. 2307 m, 17 Aug. 2015, Lazzat Nurtai 20157527-1 ( XJU) . • Qinghai Prov.: Wulan Co., Gobi desert along the way from Chaka to Wulan , 36°52'18"N, 98°55'45"E, alt. 3191 m, 19 May 2018, L. S. Wang et al. 18-58228 ( KUN) ; • Wulan Co., Gobi desert along the way from Chaka to Wulan , 36°52'18"N, 98°55'45"E, alt. 3151 m, 19 May 2018, L. S. Wang et al. 18-59258 ( KUN) ; • Wulan Co., Dulan Lake , 36°48'34"N, 98°27'06"E, alt. 2905 m, 25 Mar. 2023, S. B. Zhang et al. ZSB 23-545 ( KUN) ; • Wulan Co., Halihatu Forest Park , 37°00'41"N, 98°40'27"E, alt. 3215 m, 24 Mar. 2023, S. B. Zhang et al. ZSB 23-538 ( KUN) ; • Dulan Co., Kaoxiaotu Scenic Spot , 36°07'03"N, 98°06'23"E, alt. 3399 m, 20 Apr. 2024, S. B. Zhang et al. ZSB 24-1392 ( KUN) ; • Dulan Co., Reshui Vil. , 36°13'02"N, 98°09'07"E, alt. 3245 m, 20 Apr. 2024, S. B. Zhang et al. ZSB 24-1400 ( KUN) ; • Dulan Co., Xiangjia Vil. , 36°12'19"N, 97°01'00"E, alt. 2856 m, 15 Sep. 2020, L. S. Wang et al. 20-67122 ( KUN) ; • Datong Co. Xiegou Vil. , 36°55'42"N, 101°32'12"E, alt. 3090 m, 04 Mar. 2025, S. B. Zhang et al. ZSB 25-2149 ( KUN) ; • Dachaidan Administrative District, Snow Mountain Hot Spring Tourist Resort , 37°56'00"N, 95°22'54"E, alt. 2593 m, 16 Sep. 2023, S. B. Zhang et al. ZSB 23-1219 ( KUN) ; • Delingha Ci, Cypress Mountain , 37°28'34"N, 97°21'37"E, Alt. 3469 m, 17 Apr. 2024, S. B. Zhang et al. ZSB 24-1363 ( KUN) . • Xinjiang Prov.: Hami Ci., Balikun Co., Haiziyan Vil. , 43°35'49"N, 92°46'28"E, alt. 1543 m, 05 Sep. 2023, S. B. Zhang et al. XJ-ZSB 23-041 ( KUN) ; • Hejing Co., G 218, 42°59'40"N, 86°06'22"E, alt. 3003 m, 01 Jul. 2022, L. S. Wang et al. 22-72854 ( KUN) ; • Hejing Co., G 218, 42°54'22"N, 86°17'37"E, alt. 2221 m, 01 Jul. 2022, L. S. Wang et al. 22-72874 ( KUN) ; • Hejing Co., G 218, 42°54'23"N, 86°17'39"E, alt. 2234 m, 01 Jul. 2022, D. Liu LD 22-468 ( KUN) ; • Hejing Co., Tianshan Mountain , 42°50'40"N, 86°21'05"E, alt. 1951 m, 29 Jun. 2022, Y. Y. Zhang ZYY 22-558 ( KUN), L. S. Wang et al. 22-71718 ( KUN) ; • Hejing Co., Baluntai Town , 42°51'50"N, 86°26'35"E, alt. 2036 m, 02 Jul. 2022, X. Y. Wang et al. XY 22-896 ( KUN) ; • Hejing Co., Baluntai Town , 42°50'40"N, 86°21'06"E, alt. 1904 m, 29 Jun. 2022, X. Y. Wang et al. XY 22-773 ( KUN), L. S. Wang et al. 22-72216 ( KUN) .

Figures

Figure 6. Pleopsidium tumidulum in its habitat (18-59258 KUN).

Figure 7. Pleopsidium tumidulum (20-67124 KUN). A. Thallus; B. Lobes and apothecia; C. Section of apothecium; D, E. Young asci; F. Simple ascospores; G, H. Section of pycnidia; I. Conidia. E, F, H were captured under polarized light. Scale bars: 10 µm (D, E, F, I); 50 µm (C, G, H); 5 mm (A, B).