MycoBank MB 823219

Etymology:—The specific epithet refers to the whitish basidiocarps of this species.

Diagnosis:—Characterized by small, omphalinoid to somewhat clitocyboid basidiocarps; a white pileus; a whitish stipe with a pinkish hue at maturity; small, subglobose to short-ellipsoid basidiospores with 7−9 prominent longitudinal ribs in polar view, and a cutis-type pileipellis with slightly gelatinized, loosely interwoven hyphae. Differing from Clitopilus peri in having a larger pileus, a stipe with a pinkish hue at maturity, smaller basidiospores and a slightly gelatinized pileipellis.

Holotype:— INDIA. Kerala State: Thiruvananthapuram District, Agastyamala Biosphere Reserve, 26 September 2011, K. N. Anil Raj, AR898 (CAL 1319).

Description:— Basidiocarps small, omphalinoid to slightly clitocyboid. Pileus 7–34 mm diam., initially convex or somewhat plano-convex with or without a central depression, becoming deeply depressed or umbilicate to almost infundibuliform at maturity; surface white, weakly hygrophanous and becoming off-white with a faint grayish or pinkish tint, not striate, velutinous, tacky when moist; margin incurved to somewhat inrolled, entire or slightly wavy. Lamellae subdecurrent to decurrent, moderately crowded, initially white or off-white, becoming pale orange (6A3/ OAC695) at maturity, up to 3 mm wide, with lamellulae of 1–6 lengths; edge entire or slightly wavy, concolorous with the sides. Stipe 11–21 × 1–4 mm, central, terete, equal or slightly tapering towards the apex, cartilaginous, solid; surface initially white or whitish, developing a pinkish hue (8B3, 10D3/OAC521, OAC512) with age, finely appressed-fibrillose and pruinose all over; with profuse, white, basal mycelium. Odor not distinctive. Taste farinaceous. Spore print not obtained.

Basidiospores 4–5.5 × 3–4.5 (4.5±0.43 × 3.6±0.43) μm, Q = 1–1.66, Qm = 1.26, subglobose to ellipsoid in profile, with 7−8 prominent longitudinal ribs in polar view, colorless, slightly thick-walled. Basidia 15–22 × 5.5–8 μm, clavate, colorless, thin-walled, 4-spored; sterigmata up to 3 μm long. Lamella-edge fertile. Cheilocystidia and pleurocystidia absent. Lamellar trama subregular; hyphae 2.5–9 μm wide, colorless or pale yellow, thin-walled. Subhymenium inconspicuous. Pileus trama subregular; hyphae 3–9 μm wide, colorless or pale yellow, thin-walled. Pileipellis a cutis of loosely interwoven, slightly gelatinized hyphae often disrupted by loose ascending hyphae; hyphae 3–5 μm wide, colorless, thin-walled. Stipitipellis a cutis often disrupted by isolated or clustered ascending hyphae; hyphae 3–7 μm wide, colorless, thin-walled; terminal cells 16–21 × 4.1–7.5 μm, cylindrical-flexuose, colorless or very pale yellow, thin-walled. Caulocystidia absent. Clamp connections absent.

Habitat: — On forest soil, in small groups.

Geographical distribution range:—Known only from two localities in the Kollam and Thiruvananthapuram Districts of Kerala State, India.

Additional specimens examined:— INDIA. Kerala State: Kollam District, Kulathupuzha Sasthanada Myristica Swamp, 29 September 2010, K. N. Anil Raj AR356 (CAL 1321); Thiruvananthapuram District, Agastyamala Biosphere Reserve, 23 September 2011, K. N. Anil Raj, AR868 (CAL 1320). GenBank accessions: MF926596 (ITS), MF926595 (nLSU) and MF946579 (rpb2).

Comments:— Clitopilus albidus resembles C. peri, a species originally described from Sri Lanka (Petch 1917; Pegler 1977 a, 1986) and also from East Africa (Pegler 1977b) and India (Sathe & Daniel 1980), in having a morphologically similar pileus, decurrent lamellae, somewhat similar-looking basidiospores with almost the same number of longitudinal ribs and a hymenium devoid of both cheilo- and pleurocystidia. However, the latter species has a slightly smaller pileus (8–22 mm diam), a stipe lacking a pinkish hue at maturity, a non-gelatinized pileipellis, and larger basidiospores (6.7–8.5 × 3–4 μm). Clitopilus apalus (Berk. & Broome) Petch (1917: 326), another species described from Sri Lanka (Petch 1917; Pegler 1986) and also reported from East Africa (Pegler 1977b) and Malaysia (Baroni & Watling 1999), resembles the present species in having an umbilicate to infundibuliform pileus with a velutinous surface, deeply decurrent lamellae, and lamellae devoid of both cheilo- and pleurocystidia. However, that species differs in having larger basidiocarps, larger basidiospores (6–8.5 × 4.5–5.5 μm) with a higher number (9–11) of longitudinal ribs and a non-gelatinized pileipellis.

Comparison of the ITS, nLSU and rpb2 sequences of the present Clitopilus species with those available in GenBank shows that C. albidus is distinct. In a BLASTn search using ITS (635 bp) sequence, the closest hit was a species labelled as Clitopilus cf. scyphoides (KC176289, 93% identity). With the rpb2 (693 bp) sequence, the closest hits were Clitopilus crispus Patouillard (1913: 214) (KC816911, 92% identity)) and C. apalus (KC816906, 92% identity). Clitopilus scyphoides (Fr.) Singer (1946: 554) resembles the present species in having a similar looking white basidiocarp, decurrent lamellae and a cutis-type pileipellis (Pegler 1983); however, C. scyphoides has larger basidiospores (6–7.5 × 3–4 μm) with an oblong-ellipsoid shape and higher Qm value (Qm = 1.94). Clitopilus crispus shows no macro-morphological and microscopic similarities to C. albidus.