Xylaria tuberculosa Xiao Y. Pan, 2025

Pan, Xiaoyan, Chen, Zongzhu, Chen, Yiqing, Lei, Jinrui, Chen, Xiaohua, Wu, Tingtian & Li, Yuanling, 2025, Two new species of Xylaria (Xylariaceae, Ascomycota) associated with fallen leaves in Hainan Tropical Rainforest National Park, China, MycoKeys 112, pp. 17-34 : 17-34

Xylaria tuberculosa Xiao Y. Pan sp. nov.

Fig. 3

Holotype.

China • Hainan Province, Diaoluoshan Area of Hainan Tropical Rainforest National Park ; 18°43'33"N, 109°52'20"E; elevation 932 m; on fallen leaves, 18 June 2023, Xiaoyan Pan ( HAFFR 123 ). GenBank accession numbers PQ 483148 (ITS), PQ 498330 ( TUB 2 ), and PQ 498327 ( RPB 2 ).

Diagnosis.

Differs from X. acifer , X. hedyosmicola , X. petchii , and X. polysporicola by having smaller ascospores.

Etymology.

“ tuberculosa ” refers to the appearance of the stromata surface, which resembles segmented tubercles formed by the clustered perithecia.

Teleomorph.

Stromata upright, solitary to scattered, cylindrical, unbranched, 5–10 mm total length; acute sterile apex, 0.1 mm; fertile portion 3–6 mm long × 0.3–1 mm wide, cylindrical, composed of tightly packed perithecia; stipe glabrous, 1.8–5 mm long × 0.2–0.5 mm wide, longitudinally striate, the base slightly swollen; surface roughened, black, with half-exposed to fully exposed perithecial mounds; interior white to creamy; texture soft. Perithecia spherical, 180–350 µm diam. Ostioles papillate. Asci with eight ascospores arranged in uniseriate manner, cylindrical, 70–105 µm total length, spore-bearing part 50–70 µm long × 5–7 µm wide, stipe 25–45 µm long, with a bluing apical ring in Melzer’s reagent, tubular to slightly urn-shaped, 1.8–2.6 µm high × 1.2–2.5 µm wide. Ascospores brown, unicellular, ellipsoid, inequilateral, with narrowly rounded ends, smooth, 7–8 (– 9) × 3.3–4.3 µm (M = 7.6 × 3.8 µm, N = 40), with straight germ slit slightly shorter than the spore length on the flattened side, and a hyaline sheath visible in 1 % SDS, swollen at both ends, forming non-cellular appendages.

Remarks.

Xylaria tuberculosa forms a distinct branch in the phylogenetic tree with X. acifer , X. betulicola , X. crinalis , X. filiformis , X. hedyosmicola , and X. simplicissima , but it is morphologically different from these six species. Xylaria acifer has a needle-like stroma with flatter perithecial mounds and larger ascospores (9.3–12 × 3.7–4.7 µm), while X. betulicola , X. crinalis , X. filiformis , X. hedyosmicola , and X. simplicissima all have stromata with long sterile apices and significantly larger ascospores, measuring (9.5–21.5 × 3.5–8.5 µm). The ascospores of X. betulicola , X. crinalis , X. filiformis , X. hedyosmicola , and X. simplicissima measure (11.5 –) 12–14 (– 15) × 5–6 µm, (14 –) 15–16.5 (– 17.5) × (3.5 –) 4–5 (– 6) µm, (9.5 –) 11.5–13.5 (– 14.5) × (4 –) 4.5–5.5 (– 6) µm, (12 –) 13–15 (– 16.7) × (6 –) 6.5–7.5 (– 8.5) µm, and (15 –) 16.5–19 (– 21.5) × (5 –) 5.5–6.5 (– 7.5) µm, respectively ( Ma and Li 2018; Pan et al. 2022; Ju and Hsieh 2023).

Xylaria petchii Lloyd and X. polysporicola Hai X. Ma & X. Y. Pan are similar to X. tuberculosa morphologically, as they share cylindrical stromata growing on fallen leaves. Pan et al. (2024) described X. petchii from China, noting that this species has a variable fertile portion of the stromata and ascospores measuring (8.5 –) 10–12.5 (– 15) × (4.5 –) 5–6.5 (– 7) µm, which clearly differentiate it from X. tuberculosa . Xylaria polysporicola differs from X. tuberculosa by having a larger apical ring (2.5–4.5 µm high × 2–3.2 µm broad) and larger ascospores (( 11.5 –) 12.5–14.5 (– 15) × 5.5–8 µm) ( Pan et al. 2022). Furthermore, X. tuberculosa , X. petchii , and X. polysporicola are clearly separated in the phylogenetic tree.

Xylaria himalayensis Narula & Rawla and X. meliacearum Læssøe also resemble X. tuberculosa in morphology. Xylaria himalayensis can be distinguished by its hairy stipe and larger ascospores (( 11.5 –) 13–15 (– 15.5) × (4.5 –) 5–5.5 (– 6) µm) that lack non-cellular appendages ( Ju et al. 2018). Xylaria meliacearum can be differentiated by its stromata covered with a sulfur-yellow outer layer and larger ascospores (( 19 –) 21.5–27.5 (– 31.5) × (5 –) 5.5–7 (– 8) µm) ( Ju and Hsieh 2023). Xylaria tentaculata Ravenel ex Berk. is somewhat similar to X. tuberculosa in morphology, but X. tentaculata has significantly larger ascospores (20.6–24.4 µm × 8.9–10.8 µm) ( Kim et al. 2016).

Additional specimen examined.

China • Hainan Province, Diaoluoshan Area of Hainan Tropical Rainforest National Park ; 18°43'31"N, 109°52'19"E; elevation 929 m; on fallen leaves, 26 February 2023, Xiaoyan Pan ( HAFFR 63 ). GenBank accession numbers PQ 483149 (ITS) and PQ 498331 ( TUB 2 ) .

Figures

Figure 3. Xylaria tuberculosa (HAFFR 123) a stromata on leaves b, d stromatal surface and ostioles (arrow) c section through stroma, showing perithecia e, f ascus in 1 % SDS g ascospores in water h ascal apical ring in Melzer’s reagent i ascospore showing a slightly shorter than spore-length straight germ slit in water j ascospore showing non-cellular appendages in 1 % SDS (arrows) k, l ascospores under SEM. Scale bars: 0.5 cm (a); 200 µm (b – d); 10 µm (e – j, l); 5 µm (K).