Acervus crepusculinus Jia Y. Lin, Zhen-Chao Liu, Zhu L. Yang & Kun L. Yang, 2025

Lin, Jia Y., Liu, Zhen-Chao, Li, Guang-Mei, Yang, Zhu L. & Yang, Kun L., 2025, Three new species of Acervus (Ascomycota, Pezizales) from South China, Phytotaxa 700 (1), pp. 73-86 : 78-80

Acervus crepusculinus Jia Y. Lin, Zhen-Chao Liu, Zhu L. Yang & Kun L. Yang , sp. nov.

Registration identifier: FN572416

Etymology:— Referring to the dark orangish colour of this fungus, which resembles the dusk sky.

Diagnosis:— Differing from A. aurorinus by the larger apothecium, darker hymenium surface when fresh, brighter hymenium surface after dried, smaller ascospores, more frequently branching paraphyses and the medullary excipulum with less elements of a textura globulosa.

Type:— CHINA. Guangdong Province: Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11'32"N, 113°32'25"E, elevation 150 m, July 15, 2024, Zhen-Chao Liu, Jia Y. Lin & Kun L. Yang, S24018 ( HKAS145959 , holotype! (deposited in the Herbarium of Cryptogams in Kunming Institute of Botany of Chinese Academy of Sciences ; nrLSU: PV168197; rpb2: PV172440; tef-1α: PV172447 ); HTBM2075 , isotype!) .

Description:— Ascomata tiny to small, substipitate. Apothecium 4–18 mm broad, 1.5–8.5 mm high excluding the pseudorhiza, irregularly concave, discoid to nearly plane, with a flat to flexuous margin when mature, with a fragile, yellowish to orangish pseudorhiza. Hymenium surface smooth, tangerine orange (#F5AC4C) to carrot orange (#F79D3D) when fresh, becoming papaya red (# F99565 ) to sparrow orange (#DA9D71) after dried. External surface relatively rough, amber orange (#F1C740) to honey orange (#FFAC2A) when fresh, becoming bread orange (#F3C374) to eggshell orange (#F4C291) after dried. Context fragile, yellowish to orangish. Odour indistinct. Taste unknown.

Ascospores ellipsoid to oblong, uniseriate, nearly colourless, slightly thick- to thick-walled, non-septate, smooth, {40/2/2} (6) 6.5–8 [7.14 ± 0.51, 7.50] × 4–5 [4.50 ± 0.34, 4.50] µm, Q = (1.33) 1.40–1.78 (1.88) [1.59 ± 0.12, 1.56] including spore wall, uni- to biguttulate. Asci narrowly cylindrical, operculate, eight-spored, nearly colourless, 105–125 µm in length, with a sporiferous part 55–65 × 6–7.5 µm when mature, with a crozier at the base. Paraphyses abundant, filiform, slightly yellowish to yellowish, 3.5–5 µm wide at the middle, septate, unbranched to frequently branched. Subhymenium up to 36 µm thick, slightly yellowish to yellowish. Medullary excipulum up to 205 µm thick, composed of a gelatinized textura intricata of slightly yellowish to yellowish, 5–21 µm wide, thick-walled hyphae, mixed with a gelatinized textura globulosa of slightly yellowish to yellowish, 12–36 × 9–27 µm, thick-walled cells. Ectal excipulum up to 125 µm thick, composed of a slightly gelatinized textura globulosa to textura angularis of slightly yellowish to yellowish, 10–42 × 7.5–28 µm, slightly thick- to thick-walled cells, with abundant hyphae up to 8.5 µm wide at the middle and up to 11.5 µm wide at the inflated top and some inflated cells up to 15 µm long and 11 µm wide arising from the external surface.

Habitat and distribution:— Solitary to gregarious, on soil of subtropical forests. Currently known from South China.

Additional collections examined:— CHINA. Guangdong Province: Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11'32"N, 113°32'25"E, elevation 150 m, August 2, 2023, Zhen-Chao Liu, Jia Y. Lin & Kun L. Yang, L 23254 ( HTBM1206 (nrLSU: PV168192; tef-1α: PV172443 )) ; same location, August 26, 2024, Zhen-Chao Liu, Jia Y. Lin & Kun L. Yang, S24045 ( HTBM2125 (nrLSU: PV168198; rpb2: PV172441; tef- 1α: PV172448 )) .

Notes: —Also similar to A. heilongjiangensis , A. lusakianus and A. xishuangbannicus , but differing from A. heilongjiangensis by the larger apothecium with a pseudorhiza, smaller and uni- to biguttulate ascospores, longer asci, wider paraphyses, the medullary excipulum of a textura intricata and textura globulosa and the ectal excipulum of a textura globulosa to textura angularis; differing from A. lusakianus by the larger apothecium, ellipsoid to oblong and larger ascospores, longer and wider asci, filiform and thinner paraphyses and the medullary excipulum of a textura intricata and textura globulosa; and from A. xishuangbannicus by the larger apothecium, uni- to biguttulate and smaller ascospores, shorter and thinner asci, thinner paraphyses, the medullary excipulum of a textura intricata and textura globulosa and the ectal excipulum of a textura globulosa to textura angularis.