Macrolepiota excelsa Vellinga, Sysouph., Thongkl. and K.D. Hyde
Mycobank number: MB 838685; Facesoffungi number: FoF 09700.
Pileus 120–220 mm, when young globose to subglobose, paraboloid, expanding to campanulate, convex, umbonate or not, sometimes slightly depressed at the center, when young completely brown (6E5), later covering broken and with dark brown, irregular calotte (6F4–8; Mu. 7.5 YR 5/4, 6/6) at the center, with concolorous big patches and squamules around calotte toward the margin, patches fragile when mature; background radially fibrillose and light to greyish-brown (6D3–5; 10 YR 7/4–7.5 YR 8/6–4), slightly squarrose especially in the outer part, where the fibrils are more spread out and show the white background in between; margin irregular and exceeding lamellae. Lamellae, L = 80–130, l = 0 or 1, moderately crowded to crowded, free and remote (up to 4 mm) from stipe, off-white, broad and ventricose, up to 12 mm wide, with white floccose (cystidiose) edge. Stipe 130–350 7–10 mm at apex, 10–18 mm wide in the center, cylindrical or slightly widening downward, 23–30 mm wide at base; base in some specimens bulbous; completely covered in brown tomentose-velvety light-brown to brown, or reddish-brown (6D4–5, 6E5–6, 7.5 YR 7–6/6) covering, which breaks open into small very fine to fine horizontal bands that can form zig-zag patterns, hollow with central white cottony strand, protruding into pileus. Annulus a white descending or ascending cuff, and a flaring double part, white to yellowish-white (4A2) membranous on the upper side with a fringed edge; underside with squamules as on pileus; movable with age. Context thick and soft, white and dull in pileus; in stipe buff and hollow. Smell fungoid. Taste not observed. Spore print white.
Basidiaspore [90,3,3] 11.8–16.5 × 8.3–13.5, avl × avw = 13.2–15.3Q = 1.2–1.51× 9.2 – 11.2 µm, avQ = 1.3–1.45, in side-view broadly ellipsoid to ellipsoid, with germ pore covered by the hyaline cap, thick-walled, hyaline to pale-yellow, dextrinoid, congophilous, metachromatic. Basidia 30–40 × 11–19 µm, clavate, slightly thick-walled, 4-spored, rarely 2-spored, with basal clamp-connection. Lamella edge sterile. Cheilocystidia in chains of up to 5 elements; terminal elements 7–40 × 7–30 µm, variable in size and shape, usually subglobose, occasionally clavate, with rarely cylindrical, hyaline. Pleurocystidia not found. Pileus covering at umbo and calotte a hymenoderm made up of hemispherical to cylindrical elements, thick-walled, hyaline to pale-brown, 20–92.5 × 10–12.5 µm. Stipe covering a hymeniderm made up of cylindrical elements and hyphae, 8.7–15 µm wide. Clamp connections at the base of basidia and cheilocystidia.
Notes: Macrolepiota excelsa is a new species found in northern Thailand and northern Laos. Macroscopically this species resembles M. procera (Scop.: Fr.) Singer very much in general appearance, but it differs in the brown, not grey-brown, colors on pileus and stipe. The ITS sequence, however, does not place this species in the vicinity of M. procera, but closely related to M. detersa, M. dolichaula, the Australian sequestrate species M. turbinata T. Lebel, and M. aberdarensis Mbaluto and Otieno from Kenya. Macrolepiota detersa differs in brownish-orange to light-brown squamules on pileus and yellowish-white background, the very well-developed hanging annulus, and the branched cheilocystidia; the holotype from China showed more clavate to broadly clavate to pyriform and rarely subfusiform cheilocystidia. The pileus of M. dolichaula is much lighter colored with small brown squamules on a white background, and more clavate to sphaeropedunculate cheilocystidia. Macrolepiota aberdarensis, a species resembling M. dolichaula, is distinghuised from M. detersa by the lighter color of squamules on pileus and white background and the cheilocystidia not arranged in chains. Another species in the same clade, Macrolepiota umbonata H. J. Cho, H. Lee, and Y.W. Lim, described from South Korea differs from M. excelsa by the distinct umbo on the pileus, the white background of the pileus surface, and superior and non-membranous annulus. The stipes of M. excelsa have a central cord, similar to the stipes of Coprinus comatus (O.F. Müll.: Fr.) Pers. and Montagnea arenaria (DC.) Zeller. This is the first report of this feature outside the Coprinus comatus clade.
Fig. 1 Maximum parsimony tree of Macrolepiota Bootstrap values for maximum likelihood equal to or greater than ≥60 and Bayesian posterior probabilities ≥0.95 are placed above the branches. Abbreviations are as follows: La. = Leucoagaricus, L = Lepiota, and M = Macrolepiota. All taxon names in bold are new sequences in this study. Leucoagaricus meleagris (Gray) Singer and Lepiota cristata (Bolton) P. Kumm. are used as outgroup. Country, type, and GenBank accession number are indicated after each species name.