Hebeloma cohaerens A. Montoya & 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 cohaerens A. Montoya & Beker, sp. nov.

Figs 8 , 9

Type.

Mexico. Tlaxcala: Municipality of Panotla , 1 km al este de San Francisco Temezontla, approx. 19.3496°N, 98.2784°W, alt. approx. 2600 m, in deciduous woodland under Quercus sp., 23 Jul 2017, A. Montoya-Esquivel AME3102 (holotype TLXM 6156; isotype BR 5020224875654V; HJB17733 ); Genbank ITS ON202511 .

Diagnosis.

The short clavate-ventricose cheilocystidia, with average apical width less 6.5 µm, the small (on average less than 10 × 5.5 µm), weakly ornamented but rather strongly dextrinoid basidiospores and the whitish to cream or buff color of the pileus, differentiate this species from other Hebeloma species.

Etymology.

From Hebeloma cohaerens (adj. Latin) meaning united or joined together, to emphasize the connate habitus.

Description.

Pileus (22) 32-38 (47) mm diameter, convex, often applanate, occasionally umbonate; margin smooth, often involute, particularly when young, occasionally eroded, not hygrophanous; usually almost unicolored, usually cream or buff, sometimes slightly paler towards margin. Lamellae often adnate or adnexed, occasionally emarginate, depth up to 4 mm, white, cream to brown, with white fimbriate edge but without droplets on the lamella edge, number of full-length lamellae 70-80. Stipe (31) 37-46 (48) mm long, (5) 7-8 (10) mm diameter at median, usually cylindrical but sometimes with a clavate base, surface cream, ivory, not discoloring, fibrillose, pruinose, particularly towards apex; base with white mycelium. Context in pileus and stipe white to cream, firm, in stipe stuffed; taste not recorded, smell earthy. Spore deposit color not recorded.

Basidiospores based on n = 64 spores of the holotype, 5% to 95% percentile range 8.6-10.5 × 4.9-5.7 µm, with median 9.4 × 5.3 µm and av. 9.5 × 5.3 µm with S.D. length 0.57 µm and width 0.26 µm; Q value 5% to 95% percentile range 1.64-1.95, with median 1.79 and av. 1.78 with S.D. 0.10; spore size based on four collections medians 9.1-9.5 × 5.3-5.6 µm and av. 9.1-9.5 × 5.3-5.5 µm with av. S.D. length 0.50 µm and width 0.30 µm, av. Q 1.65-1.78, amygdaloid, occasionally limoniform, with small apiculus and rounded apically, often subacute, with a distinct thinning of the apical wall and sometimes a papilla, usually guttulate with one or sometimes more oily drops, at most weakly ornamented (ornamentation only visible under immersion), with a perispore hardly loosening, rather strongly dextrinoid, becoming medium reddish brown in Melzer’s reagent (O1/2; P0; D3); yellow brown in KOH. Basidia 22-27 × 5-7 µm, with av. Q 3.7-3.8 µm, cylindrical to clavate, hyaline, 4-spored. Cheilocystidium width near apex holotype 5% to 95% percentile range 4.7-7.7 µm, with median 6.0 µm and av. 6.1 µm with S.D. 1.0 µm; across four collections median 5.6-6.4 µm and av. 5.5-6.3 µm; examining approx. 20 selected cheilocystidia of each of the four collections yields a range for the avs. of 33-36 × 5.5-6.3 × 3.5-4.1 × 5.5-6.6 µm and 33 × 6.1 × 4.1 × 6.5 µm av. for holotype. Cheilocystidium av. ratios A/M: 1.49-1.63, A/B: 0.86-1.03, B/M: 1.59-1.88, mainly clavate-ventricose, often with one or two septa. Pleurocystidia absent. Caulocystidia similar to cheilocystidia but larger, up to 90 μm long. Pileipellis an ixocutis with an epicutis up to 110 µm thick, with gelatinized, hyphae up to 6 µm wide; subcutis cream to pale yellow, and the trama below the cutis made up of cylindrical, often ellipsoid cells, up to 14 µm wide. Clamp connections present throughout the basidiome.

Ecology and distribution.

In deciduous or mixed woodlands apparently associated with Quercus or Pseudotsuga . Growth habit mainly caespitose, sometimes with a few scattered basidiomes. To date, all collections of Hebeloma cohaerens recorded from Tlaxcala at altitudes of 2600 m or more.

Additional collections examined.

Mexico. Tlaxcala: Municipality of Panotla, 1 km al este de San Francisco Temezontla, approx. 19.3496°N, 98.2784°W, alt. approx. 2600 m, in deciduous woodland under Quercus sp., 23 Jul 2017, A. Montoya-Esquivel (TLXM AME3101, HJB17732). Municipality of Panotla, 1 km al este de San Francisco Temezontla, approx. 19.3496°N, 98.2784°W, alt. approx. 2600 m, in deciduous woodland under Quercus sp., 23 Jul 2017, A. Kong (TLXM AK17-08, HJB17737). Municipality of Terrenate, Rancho el pozo, approx. 19.5407°N, 97.9046°W, alt. approx. 2900 m, on soil in woodland under Pseudotsuga sp., 13 Jul 1995, Galindo-Flores (TLXM GF1866, HJB16779).

Remarks.

The small, short clavate-ventricose cheilocystidia, together with the small rather smooth, rather strongly dextrinoid basidiospores, support the placement of this species within Hebeloma sect. Theobromina . Within this section the pale cream to buff pileus color together with the caespitose habitus is unique.

The description was based on just four collections all from the same region of Mexico, and is not known from any other location. More records for this species will help to define better its morphological characters and its biogeographic preferences.

The minimum interspecific distance between the ITS sequences of H. cohaerens and sequences from other species is around 1.2%. The BLAST result of the type sequence of H. cohaerens against UNITE resulted in a hit of a soil sample sequence, pointing towards UNITE SH1563973.08FU (98.5% level). This SH includes two independently generated sequences from California (UDB0767851, soil sample, Tedersoo et al. 2021; DQ822802, basidiome, Point Reyes National Seashore Reserve, under Pinus muricata , Peay et al. 2007) that differ by around 0.5% from the sequences assigned to H. cohaerens , but match no other species. These results suggest that H. cohaerens may occur in the US (California) and the UNITE SH corresponding to H. cohaerens is likely to be SH1563973.08FU.

Figures

Figure 8. A-B basidiomata, holotype of Hebeloma cohaerens TLXM 6156 (HJB 17733). Photos A. Kong.

Figure 9. Holotype of Hebeloma cohaerens TLXM 6156 (HJB 17733) A basidiospores x 1600 - B spore ornamentation x 1600 C basidiospores in Melzer's reagent x 1600 D-E cheilocystidia x 1000 F basidia x 1000 G cheilocystidia x 500 H caulocystidia x 500 I epicutis hyphae x 1000 J subcutis x 1000 K cutis x 125. All in KOH, except C. Scale bars: 5 µm (A-F); 10 µm (G-J); 50 µm (K). Photos H. J. Beker.