Hydnobolites oaxacanus de la Fuente & J. García, 2022

Fuente, Javier Isaac De La, García-Jiménez, Jesús, Martínez-González, César Ramiro, Ayala-Vásquez, Olivia, Del-Valle, Juan Francisco Hernández, Florez, Marcos Sánchez- & Peña-Ramírez, Rafael, 2022, Hydnobolites oaxacanus (Pezizales, Ascomycota), a new species from Mexico, Phytotaxa 559 (1), pp. 73-80 : 77

Hydnobolites oaxacanus de la Fuente & J. García , sp. nov. ( Fig. 3 ).

Mycobank no. MB 841759

Type: — MEXICO. Oaxaca: Nochixtlán municipality, road to Apoala , 17°28’33” N, 97°12’21 “W, 2281 m.a.s.l., 19 August 2018, García 21382 (Holotype ITCV [JGARCIA-21382- ITCV]) .

Diagnosis: — Hydnobolites oaxacanus differs from other species within the genus by the 4-spored asci, ascospores of 17–45 × 15–20 µm, and the putative association with Quercus castanea .

Description: — Ascocarps hypogeous, 8–25 × 5–11 mm, globose to subglobose, some lobated, white, with scattered orange mycelial strands, turning pale brown when touched, minutely pubescent. Odor and taste mild. Gleba pale gray, with fertile tissue separated by white veins, connected with the peridium, columella absent. Odor and taste fungoid. Peridium 120–300 µm thick, composed of interwoven or prostrated hyphae, loose at the external side, compacted near the gleba, with some erected hyphae 17–30 × 5–8 µm, tubulose or clavate, some with rugose thin-walled. Trama 20–45 µm composed of interwoven hyphae, 2–10 µm in diameter, tubulose, rarely inflated, septate, sometimes branched, thin-walled. Asci 77–95 × 62–78 µm, globose or pyriform, with pedicel up to 20 µm long, cylindric to inflated, hyaline, with oily content, tetrasporic, thin-walled. Ascospores 17–45 × 15–20 µm (W=18, L= 25, Q=1.13–2.25, N=30) broadly ellipsoid, ellipsoid, rarely subglobose or cylindrical, hyaline, alveolate-reticulate, up to 7–9 alveoli longwise, 6–8 sidewise, angular (5–7 sides), heterodiametric or rarely irregular, 3–5 µm in diameter, projected up 7 µm, thin-walled.

Etymology: —Named oaxacanus in reference to the Mexican state of Oaxaca, where the species was discovered.

Distribution: —Known from the type locality, growing hypogeous in Quercus-Pinus dry mixed forest under Quercus castanea Née.

Comments: —The most remarkable characteristics of the new species are the 4-spored asci and the large ascospores. Most of the Hydnobolites species have 8-spored asci except Hydnobolites javanicus Höhn. , which has 1–3-spored asci. Hydnobolites javanicus differs from H. oaxacanus in the number of ascospores per asci and the ascospore size. Hydnobolites baodingensis Wu & Lan (1993: 1021) have 8-spored asci, ascospores of 15–21 µm and associated with Zea (L), Dyospiros (L) and Setaria P. Beauv ( Wu et al. 1993). Both species mentioned above lack molecular evidence, and some authors ( Smith and Schmull 2011; Li et al. 2019) believe that these species should not be placed in Hydnobolites due to the presence of an episporium in H. javanicus and the putative saprobious lifestyle of H. baodingesis . The new species also differs from the Asian species. It can be easily separated from H. caniculatus L. Fan, M. Chen & T. Li (2019: 406) , which have folded gleba, whereas H. oaxacanus have solid gleba. Hydnobolites roseus L. Fan, M. Chen & T. Li (2019: 408) have a pinkish peridium, very different from the whitish color present in H. oaxacanu s. Both H. shianxiensis L. Fan, M. Chen & T. Li (2019: 409) and H. yunnaensis L. Fan, M. Chen & T. Li (2019: 412) have 8-spored asci, smaller ascospores and bigger alveoli ( Li et al. 2019). It is also different from the American species. Hydnobolites californicus E. Fisch. (1909: 194) have smaller ascospores and bigger alveoli ( Gilkey 1916). The new species share some characteristics with H. cerebriformis like the whitish ascoma that turns orange when touched ( Cázares et al. 1992) nevertheless, it differs in the ascospore size and ornamentation ( Trappe et al. 2007).

Figures

FIGURE 3. Hydnobolites oaxacanus (Holotype). A. Details of the peridium and gleba. B. Asci and ascospore showing the alveolate ornamentation. C. Detail of the ascospore ornamentation. Scale bar: 10 mm (A); 100 µm (B); 20 µm (C).