Hebeloma magnicystidiatum A. Kong & Beker, sp. nov.

Eberhardt, Ursula, Kong, Alejandro, Montoya, Adriana, Schuetz, Nicole, Bartlett, Peter & Beker, Henry J., 2022, Not (only) poison pies - Hebeloma (Agaricales, Hymenogastraceae) in Mexico, MycoKeys 90, pp. 163-202 : 163

Hebeloma magnicystidiatum A. Kong & Beker, sp. nov.

Fig. 10

Type.

Mexico. Tlaxcala: Municipality of Totolac, Tepeticpac , 19.3457°N, 98.2226°W, alt. approx. 2400 m, on the ground in woodland under Pinus sp. and Quercus sp., 29 Aug. 1990, A. Estrada-Torres AET3093 (holotype TLXM 6157; isotype BR 5020224873599V; HJB16795 ); GenBank ITS ON202534 .

Diagnosis.

The amygdaloid, non-dextrinoid, rather strongly ornamented spores with average Q value less than 1.6 and the capitate-stipitate cheilocystidia with average width at the apex greater than 9.5 µm distinguish this species from all other known Hebeloma species.

Etymology.

From magni - (Latin, composite) meaning large and cystidiatus to emphasize the large capitate-stipitate cheilocystidia.

Description.

Pileus 19-26 mm diameter, convex, surface dry, finely tomentose, cuticle separable, reddish yellow to brown in the center, and pale orange towards the margin. Lamellae emarginate, white, cream to orange brown as the spores mature, with a white fimbriate edge, and about 60 full-length lamellae. Stipe 10-21 mm long, 4-6 mm diameter at median, cylindrical, surface whitish but discoloring brown from the base upwards, with age or handling, fibrillose, at apex pruinose. Context in pileus white to cream, firm, in stipe stuffed, initially white to cream but becoming brown with age and handling, becoming hollow with age; taste fungal to sweet, smell raphanoid. Spore deposit not recorded.

Basidiospores based on n = 44 spores of the holotype, 5% to 95% percentile range 9.7-11.6 × 6.4-7.6 µm, with median 10.5 × 7.0 µm and av. 10.5 × 7.0 µm with S.D. length 0.62 µm and width 0.42 µm; Q value 5% to 95% percentile range 1.40-1.62, with median 1.49 and av. 1.50 with S.D. 0.07; amygdaloid, often limoniform, with small apiculus and rounded apically, often subacute to acute, with a distinct thinning of the apical wall and sometimes a clearly visible papilla, not guttulate, usually rather strongly ornamented, ornamentation visible even without immersion, with perispore at most somewhat loosening in a few spores, an indistinct brownish tint in Melzer’s reagent (O3; P1; D1); yellow-brown in KOH. Basidia 27.5-35 × 7.5-9 µm, with av. Q 3.9, cylindrical to clavate, without pigmentation, 4-spored. Cheilocystidium width near apex holotype 5% to 95% percentile range 6.1-14.3 µm, with median 9.1 µm and av. 9.7 µm with S.D. 2.61 µm; examining approx. 20 selected cheilocystidia of the holotype yields a range for the avs. of 55 × 9.7 × 7.3 × 4.3 µm av. and cheilocystidium av. ratios A/M: 2.58, A/B: 2.67, B/M: 0.95; mainly capitate-stipitate, unfortunately many collapsed in exsiccata. Pleurocystidia absent. Caulocystidia similar to cheilocystidia but larger, up to 80 μm long. Pileipellis an ixocutis; epicutis up to 110 µm thick, with gelatinized hyphae up to 7 µm wide; subcutis yellow; and the trama below the cutis made up of cylindrical or occasionally ellipsoid cells up to 17 µm wide. Clamp connections present throughout the basidiome.

Ecology and distribution.

In woodland on the ground with Comarostaphylis and Quercus . Growth habit scattered. To date, with only one collection of this species, not possible to describe its distribution and ecology.

Remarks.

With its amygdaloid, hardly dextrinoid basidiospores and capitate-stipitate cheilocystidia, morphologically this taxon clearly belongs to Hebeloma sect. Denudata and there to H. subsect. Crustuliniformia . The amygdaloid spores with rather small average Q value separate this species from all other studied Hebeloma from our database with more than 10,000 collections. While this may suggest that this is a rare species, we have insufficient Hebeloma collections from Mexico to reach such a conclusion. The single collection was collected in the 1990s, thus the only loci we could amplify were ITS and mitSSU variable regions V6 and V9.

The phylogenetic placement of H. magnicystidiatum within H. sect. Denudata is unresolved. As pointed out before (e.g. Eberhardt et al. 2016, 2022b; Beker et al. 2016), the more species rich subsections of H. sect. Denudata ( H. subsects Clepsydroida and Crustuliniformia ) are not supported molecularly. In terms of ITS, the most similar species was H. sordidulum ( H. subsect. Clepsydroida ) with similarity values ≤ 98.7%. Possibly H. magnicystidiatum will correspond to a UNITE SH at the 99% or 98.5% level once sequences of this species are included in the system. Morphologically, the capitate-stipitate cheilocystidia together with the amygdaloid spores with av. Q less than 1.6 are sufficient characters to separate this species from members of H. sect. Clepsydroida , such as H. cavipes , H. matritense , H. sordidulum and H. vaccinum .

Figures

Figure 10. Holotype of Hebeloma magnicystidiatum TLXM 6157 (HJB 16795) A Basidiospores x 1600 B spore ornamentation x 1600 C basidiospores and D spore ornamentation in Melzer's reagent x 1600 E basidium x 1000 F-H cheilocystidia x 1000 H cheilocystidia x 500 I caulocystidia x 500 J cutis x 125 K epicutis hyphae x 500 L subcutis x 500. All in KOH, except C-D. Scale bars: 5 µm (A-G); 10 µm (H-I, K-L); 50 µm (J). Photos H. J. Beker.