Lentinus arcularius (Batsch) Zmitr.
Index Fungorum number: IF543135; Facesoffungi number: FoF 14090
Pileus 10–40 mm diam., convex to applanate, deeply depressed at center, smooth, slightly glabrous, brown (6E4–6) when young, becoming light brown (6D4–6) when mature; margin attached with long spine–like, 2–5 mm long, fragile when mature, white to pale arrange (5A–3). Pore decurrent, white when young, becoming orange–white to pale orange (5A2–3) with age, often rounded, mostly angular to radially elongated, 1–2 mm long, oblong at stipe zone, 3–4 mm long, with white eroded margin. Stipe central, 2–4 × 15–50 mm, cylindrical, smooth, white to concolorous with pileus with age, sometimes darker with dark brown (6F5–8), occasionally with white hyphae at base zone. Annulus absent. Context white at pileus and stipe, fleshy–tough to leathery. Oder and Taste not observed. Spore print white. Hyphal system at tramal structure dimitic with generative hyphae and skeletal–ligative hyphae; generative hyphae thin–walled, hyaline, with clamp connection, 3–13 µm wide, cylindrical to oblong with wider at middle zone; skeletal–ligative hyphae thick–walled, hyaline, up to 7–14 µm wide, thick–walled, with 2–5 lateral branches. Hyphae of long spine at marginal zone of pileus clustered with cylindrical elements with rounded or attenuate apex, slightly thick–walled, hyaline, very long, 5–7 µm wide at base, 2–3.5 µm wide at apex zone. Basidiospores 6.5–10 × 3–3.5 µm, oblong to cylindrical, thin–walled, hyaline, non–dextrinoid. Basidia clavate to 15–20 × 4.5–6.5 µm, thin–walled, hyaline, 4–spored. Cheilocystidia 25–40 × 4.5–7 µm, cylindrical with rounded apex, with 2–3 branches at basal zone, hyaline, slightly thick–walled. Pleurocystidia absent.
Habitat and distribution in Thailand: solitary or in a cluster, on dead wood in several forest types from low to high elevations. High distribution in northern and southern Thailand by this study. It was reported to distribute in northern and northeastern Thailand as Polyporus arcularius (Batsch) Fr. by Chandrasrikul et al. (2011) and Hjortstam & Ryvarden (1982).
Material examined: Thailand; Chiang Mai Province, Mueng District, Hua Doi Village, 13 July 2018, P. Sysouphanthong, PS2018–40 (MFLU22–0020); Chiang Rai Province, Muang District, Khun Korn Village, 27 August 2018, P. Sysouphanthong, PS2018–131 (MFLU22–0022); Chiang Rai Province, Pha Ngae Village, Pa Daed District, 29 August 2018, P. Sysouphanthong, PS2018–134 (MFLU22–0023); ibidem, 29 August 2018, P. Sysouphanthong, PS2018–162 (MFLU22–0024); ibidem, 29 August 2018, P. Sysouphanthong, PS2018–163 (MFLU22–0025); ibidem, 29 August 2018, P. Sysouphanthong, PS2018–165 (MFLU22–0026); Nan Province, Muang District. Phu Xang, 11 September 2018, P. Sysouphanthong, PS2018–186 (MFLU22–0027); Chiang Mai Province, Mae Taeng District, Pha Deng Village, 7 August 2018, coll. P. Sysouphanthong, PS2018–95 (MFLU22–0021).
Notes: Thai collections have thin and various colours of pileus being light brown to brown, with short or long white spines at the marginal zones of the pileus, white to pale orange elongated pores, and central attachment and cylindrical stipe. Zmitrovich (2018) placed L. arcularius in Lentinus subgenus Polyporellus (P. Karst.) Zmitr., consisting of species with polyporoid basidiomata. Thai specimens of L. arcularius in this study clustered well with those specimens from Argentina, China, India, Japan, Malaysia and Thailand. Lentinus tricholoma (Mont.) Zmitr. appears similar to L. arcularius by morphology, but differs in having rounded or circular pores with smooth edges, while L. arcularius has elongated pores, and molecular data do not support that they belong to the same clade and is constant with Seelan eat al. (2015). Lentinus brumalis (Pers.) Zmitr. is similar to L. arcularius by pileus colour and pore shape, but it has a thick pileus and short stipe, and absence of spines at marginal zone of pileus. Molecular data analysis in this study shows that they are in a clade with Polyporellus II that includes species with elongated to angular pores, and this is consistent with Seelan et al. (2015). Lentinus brumalis was recorded in northern Thailand by Hjortstam & Ryvarden (1982), but we do not find it in this study. Lentinus substrictus (Bolton) Zmitr. & Kovalenko has much larger basidiomata, greyish brown colour of pileus, absence of spine at pileus margin, and greyish brown squamules on a thick stipe (Zmitrovich & Kovalenko 2016).
Fig. 1 Maximum likelihood tree of Lentinus based on ITS–LSU sequences. The taxa in blue are specimens from Thailand. Support values of ML and MP≥70% and BI ≥ 0.95 are indicated on the nodes. Specimen voucher numbers are indicated after species names. Ganoderma boninense Pat. was used as the outgroup.
Fig. 2 Macrocharacters of Lentinus arcularius. a MFLU22–0021. b MFLU22–0022. c MFLU22–0023. d MFLU22–0025. e–f MFLU22–0024. g MFLU22–0026. h MFLU22–0020. i MFLU22–0027.