Lactifluus albomembranaceus De Wilde & Van de Putte, 2016

Crop, Eske De, Putte, Kobeke Van De, Wilde, Serge De, Njouonkou, André-Ledoux, Kesel, André De & Verbeken, Annemieke, 2016, Lactifluus foetens and Lf. albomembranaceus sp. nov. (Russulaceae): look-alike milkcaps from gallery forests in tropical Africa, Phytotaxa 277 (2), pp. 159-170 : 162-167

Lactifluus albomembranaceus De Wilde & Van de Putte sp. nov. FIGURES 2a–b , 3 , 4 , 5a–b

Mycobank: MB 815846

Diagnosis: A medium-sized species of ca. 4–5 cm diam., which resembles Lactifluus foetens at first sight but differs on several levels. Macroscopically it is characterised by a white and often translucent pileus when fresh, together with white lamellae and a white to cream-yellow coloured stipe. Microscopically, this species has a lampropalisade as a pileipellis with terminal hair-like elements shorter than those of Lf. foetens , broadly ellipsoid basidiospores, basidiospore ornamentation of isolated warts that are often connected by fine lines but never forming a reticulum, slender basidia and rather long marginal cells.

Etymology:—Contraction of ‘albo’ and ‘membranaceus’, referring to the white colour and translucent aspect of the pileus.

Holotypus: — CAMEROON. Western region: Noun division, Koutaba subdivision, Mamevouo village, elev. 1111m, N5°38.97’ E10°51.08’, gallery forest in savannah region near a river and surrounded by farmland, with Uapaca guineensis Müller Argoviensis (1864: 517) , 10 May 2012, E. De Crop 12-046 (GENT!).

Description: —Pileus 40–55 mm diam., firm, planoconvex with central depression, translucent when fresh and at maturity; margin slightly involute when young, deflexed when older, concentrically wrinkled, often striate to sulcate up to around 1 cm from the margin; pellis chamois leather-like, wrinkled and granulose, yellowish when juvenile, then becoming pure white, after collecting becoming yellowish cream (2–3A2), becoming brownish after bruising. Lamellae adnate with distinct decurrent tooth, with lamellulae of different lengths, rather distant (6 L+11 l/cm), whitish, concolorous with pileus, becoming brownish after bruising, thin but not brittle; edge entire, concolourous. Stipe 40–50 × 7–10 mm, irregularly cylindrical to tapering downwards, sometimes slightly swollen at the base, sometimes curved, centrally attached to pileus; pellis chamois leather-like, slightly longitudinally wrinkled, concolourous with pileus or with a cream to yellowish colour, becoming brownish after bruising. Context firm, solid when young, becoming stuffed when older; white, not changing with age, becoming brownish when cut (especially pileus). Odour sometimes strong and slightly unpleasant. Taste slightly sweetish to nutty. Latex abundant, white, slowly turning brownish (6E7–8) when staying in contact with the basidiocarp, taste mild. Chemical reactions: context quickly turning pink with FeSO4; stipe surface, lamellae and context unchanging with guaiac.

Basidiospores globose to broadly ellipsoid, 5.9– 6.9–7.3 –8.1(–8.4) × 5.0– 5.7–6.1 –7.0(–7.1) μm (Q = 1.09– 1.17– 1.22 –1.36(–1.41), n = 138); ornamentation amyloid, composed of isolated warts (up to 1 μm high), often connected by low ridges, but not forming a reticulum; plage centrally to almost totally amyloid. Basidia 53–80(–90) × 7–9(–10) μm, very slender, subcylindrical to subclavate, thin-walled, 4-spored; content oil-like to granular or needle-like. True pleurocystidia absent. Pleuropseudocystidia very abundant, mostly emerging, 3–7 μm diam., cylindrical to irregularly cylindrical, occasionally branched; apex obtuse to subcapitate; content oil-like to granular or needle-like. Lamellae-edge sterile; marginal cells 7–55(–65) × 4–6(–9) μm, often septate to multiseptate with terminal cells up to 50 μm long, subclavate to cylindric or tortuous, occasionally tapering upwards, obtuse, thin-walled to refringent or slightly thick-walled (up to 0.5 μm, rarely 1 μm). Hymenophoral trama mixed, with abundant lactifers. Pileipellis a lampropalisade, up to 255 μm thick; terminal elements 20–120(–150) × 5–12 μm, subcylindrical to subclavate, often irregularly shaped, obtuse, occasionally septate, thick-walled (up to 1 μm); subpellis composed of mostly rounded to elongated, thick-walled cells, 10–35 × 8–20 μm. Stipitipellis a lampropalisade. Clamp-connections absent.

Ecology:—Found in the Guineo-Sudanian transition zone in gallery forests with Uapaca guineensis and Berlinia grandiflora (Vahl) Hutchinson & Dalziel (1928: 343) .

Distribution:—Known from Burkina Faso, Cameroon and Togo.

Studied material:— CAMEROON. Western region : Noun division, Koutaba subdivision, Mamevouo village, elev. 1118m, N5°38.88’ E10°51.05’, gallery forest in savannah region near a river and surrounded by farmland, with Uapaca guineensis , 10 May 2012, E. De Crop 12-045 ( GENT!) ; Ibidem , elev. 1111m, N5°38.97’ E10°51.08’, gallery forest in savannah region near a river and surrounded by farmland, with Uapaca guineensis, E. De Crop 12-046 (Holotypus, GENT!) ; Ibidem , elev. 1129m, N5°39.1’ E10°50.88’, gallery forest in savannah region near a river and surrounded by farmland, with Uapaca guineensis, E. De Crop 12-052 ( GENT!) ; Ibidem , elev. 1113m, N5°38.97’ E10°51.03’, gallery forest in savannah region near a river and surrounded by farmland, with Uapaca guineensis, E. De Crop 12-054 ( GENT!) .

TOGO. Central province: Alédjo Wildlife Reserve, N09°16.460’ E01°12.416’, gallery forest, with Berlinia grandiflora , 11 July 2007, A. De Kesel 4284 ( BR MYCO 158446–45!).

Figures

FIGURE 2. Basidiocarps of Lf. albomembranaceus: a) holotype EDC 12-046 (photo by E. De Crop) and b) ADK 4284 (photo by A. De Kesel) and Lf. foetens: c) ADK 4283 (photo by A. De Kesel) and d) AV 11-176 (photo by A. Verbeken).

FIGURE 3. Lf.albomembranaceus: a) basidiocarps,b) pleuropseudocystidia,c) basidiospores, d) basidia,e) marginalcells (all from holotype EDC 12-046, scale bar = 10 μm). Illustrations by K. Van de Putte and S. De Wilde.

FIGURE 4. Lf. albomembranaceus: section through the pileipellis (all from holotype EDC 12-046, scale bar = 10 μm). Illustration by K. Van de Putte.

FIGURE 5. Scanning electron microscope images of basidiospores of Lf.albomembranaceus (all from holotype EDC 12-046): a) overview, b) detail on basidiospores and Lf. foetens (all from holotype ADK 2840): c–d) detail on basidiospores (scale bars = 1 μm).