Rhodocollybia brevipes K. N. A. Raj & Manim., 2018

Deepna Latha, K. P., Anil Raj, K. N. & Manimohan, Patinjareveettil, 2018, Two new species of Rhodocollybia from tropical India, Phytotaxa 340 (2), pp. 157-166 : 161-164

Rhodocollybia brevipes K. N. A. Raj & Manim. , sp. nov. Figs. 2A–H

MycoBank MB 823799

Etymology:— brevis (Latin), short; pes (Latin), foot; refers to the short stature of this species.

Diagnosis:—Characterized by tricholomatoid basidiocarps with a reddish brown, fibrillose pileus; a short, reddish brown stipe; thin- to slightly thick-walled, lacrymoid, cyanophilous basidiospores; versiform cheilocystidia and clamped hyphae. Differing from R. pandipes in having smaller basidiocarps, pale orange, adnate lamellae with a small, decurrent tooth, smaller, lacrymoid basidiospores, a stipitipellis devoid of caulocystidia and a distinctive nrITS sequence.

Holotype:— INDIA. Kerala State: Idukki District, Munnar, on the way to Mattupetti Dam , 25 August 2011, K. N. Anil Raj AR849 ( CAL 1525 ).

Description:— Basidiocarps small to medium-sized, tricholomatoid. Pileus 32–59 mm diam., broadly convex; surface reddish brown (8D 4, 8E 4/OAC612, OAC611) all over, not hygrophanous, not striate, dry, finely appressed-fibrillose all over; margin slightly incurved or decurved, crenate, rather fissile. Lamellae adnate with a small decurrent tooth, crowded, pale orange (6A3/OAC634), up to 6 mm wide, with lamellulae of 1–3 tiers; edge crenate or rather undulate, concolorous with the sides. Stipe 36–39 × 7–17 mm, central, terete or slightly compressed, rather tapering towards the apex, solid; surface concolorous with the pileus, finely appressed-fibrillose as well as minutely pruinose all over, denser towards the apex and the base, with thick, whitish basal mycelium. Odor and taste not distinctive. Spore print not obtained.

Basidiospores 3.5–5 × 2.5–4 (4.2±0.44 × 3.17±.41) μm, Q = 1.12–1.67, Qm = 1.35, lacrymoid, hyaline, smooth, thin- to slightly thick-walled, cyanophilous, inamyloid. Basidia 16–27 × 4–6 μm, clavate, hyaline or with a pale yellow plasmatic pigment, thin-walled, 4-spored; sterigmata up to 3 μm long. Pleurocystidia absent. Lamella edge heterogeneous. Cheilocystidia 16–24 × 3.5–10 μm, scattered, versiform to cylindro-flexuous, clavate, fusiform, or broadly clavate with a median constriction, thin-walled, hyaline. Lamellar trama subregular; hyphae 4–18 μm wide, thin-walled, hyaline, inamyloid. Pileus trama loosely interwoven; hyphae 3–19 μm wide, thin-walled, hyaline, inamyloid. Pileipellis a cutis; hyphae often with short lateral protrusions or branches; 3–10 μm wide, thin-walled, hyaline. Stipitipellis a trichoderm composed of compactly arranged flexuous hyphae; hyphae 2–6 μm, thin-walled, hyaline, inamyloid. Caulocystidia absent. Clamp connections present on all hyphae.

Habitat: — Growing in small groups on a mud-wall among moss in a eucalypt plantation.

Geographical distribution range:—Known only from the type locality in Kerala State, India.

Comments:—Characters such as the fleshy, tricholomatoid basidiocarps with a smooth, convex pileus and crowded, pale orange lamellae, the cyanophilous and thick-walled basidiospores, the cutis-type pileipellis and the nrITS sequence data lead the present species to the genus Rhodocollybia ( Mata et al. 2004) . Rhodocollybia pandipes Halling and J. L. Mata (in Mata et al. 2004: 346), a species from the neotropical montane forests shows some similarities to R. brevipes in having a similar colored, convex pileus with a fibrillose surface, a fibrillose stipe, a subregular lamellar trama, heterogeneous lamella edges with cheilocystidia, a hymenium devoid of pleurocystidia, thin- to thick-walled, cyanophilous basidiospores, a cutis-type pileipellis and clamped hyphae. However, R. pandipes differs from R. brevipes in having slightly larger basidiocarps (70 mm), adnexed lamellae, broadly ellipsoid to subovoid, and larger (4.4–9.6 × 2.8–4.8 μm) basidiospores, and the occasional presence of caulocystidia.

Closest hits in a BLASTn search in GenBank using the nrITS sequences (682 bp) of R. brevipes were Rhodocollybia prolixa (as Rhodocollybia prolixa var. distorta ; AF505748; Identity = 93%) and R. badiialba (EU486446; Identity = 89%). Rhodocollybia prolixa ( Fries 1838: 84) Antonín, Halling & Noordeloos (in Antonín et al. 1997: 365, as R. prolixa var. distorta ) can be distinguished from R. brevipes in having a larger (100 mm), wet, yellowish, hygrophanous pileus, adnexed, narrow (3 mm) lamellae, a longer (120 mm), grayish orange stipe, subglobose, weakly dextrinoid, acyanophilous basidiospores, short-clavate, occasionally lobed cheilocystidia, stipitipellis with caulocystidia, a pungent odor, a gregarious habit and a different habitat among Quercus species. Rhodocollybia badiialba ( Murrill 1916: 369) Lennox (1979: 224) differs from R. brevipes in having a larger (115 mm), dark chestnut to fulvous, hygrophanous, lubricous and umbonate pileus, longer, a hollow and flesh-colored stipe, globose to broadly ovate, dextrinoid basidiospores, the presence of occasionally 2-spored and dextrinoid basidia, the absence of cheilocystidia, a gelatinized cutis-type pileipellis, basidiocarps with a pungent odor and a bitter taste and caespitose habit on decayed logs among dense conifer woods.

The phylogram ( Fig. 3 .) inferred from the Maximum Likelihood analysis depicts the two new Indian species nesting among other species of Rhodocollybia . All species of Rhodocollybia included in the analysis together formed a distinct group. Within this group, R. ciliatomarginata was found to be a discrete species within the /butyracea group with strong ML bootstrap support (98 % BS). Rhodocollybia brevipes was found to be clustered in the /maculate group and it pairs with R. prolixa var. distorta with maximum bootstrap support (100% BS). However, R. prolix a var. distorta , a species reported from Costa Rica is morphologically different from R. brevipes and also, a pairwise alignment of the nrITS sequences (AF505748/MF803834) of these two species showed only 93% sequence similarity.

The genus Rhodocollybia is often distinguished by the presence of dextrinoid and cyanophilous basidiospores ( Mata et al. 2004). Interestingly, R. ciliatomarginata is devoid of both these characters. Rhodocollybia brevipes , on the other hand, possesses cyanophilous but inamyloid basidiospores. Lennox (1979) and Halling (1989) also have pointed out the absence or the scarcity of dextrinoid basidiospores in some Rhodocollybia species. Mata et al. (2016) also observed the inconsistency of these characters for recognizing the genus. So far, no species of Rhodocollybia have been reported from South Asia. Hence, the discovery of these two new species ( R. ciliatomarginata and R. brevipes ) also forms the first record of the genus Rhodocollybia from South Asia. Remarkably, both the new species were collected from the highlands of Kerala where cooler climate prevails. This is in tune with the discovery of Rhodocollybia in the montane regions of Central America ( Mata et al. 2016). It seems this genus has a preference for cooler climate.

Figures

FIGURE 2. A–H: Rhodocollybia brevipes (CAL 1525, holotype).A & B. Basidiocarps; C. Basidiospores; D. Basidium; E. Cheilocystidia; F. Pileipellis. G. Stipitipellis; H. Terminal element of stipitipellis; I. Clamp connection on hyphae of stipitipellis. Scale bars: A-B = 10mm; C–E, H, I = 10 μm; F–G = 20 μm. Photos by K. N. Anil Raj.

FIGURE 3. ML phylogram based on nrITS sequence data showing the placement of R. ciliatomarginata and R. brevipes within the genus Rhodocollybia. Values at nodes indicate bootstrap support. BS values ≥50% are shown. Scale bar indicating the number of substitutions per site.