Sutorius pseudotylopilus Vadthanarat, Raspé and Lumyong
Pileus 5.0–12 cm in diameter, at first convex with inflexed margin becoming planoconvex to depressed with straight margin, margin slightly exceeding (1–2 mm); surface even to subrugulose, dull, matted tomentose to cracked tomentose with age, patchy, grayish brown to reddish brown, brown (9–10E3–4, 7F5–6, 8F3–4). Pileus context 10–20 mm thick halfway to the margin, yellowish white to orange white (4A2 to 5A2), with scattered small groups of reddish brown (9F6–7) encrustations, slowly slightly reddening when cut. Stipe central, terete, cylindrical to slightly tapering downward, 7.5–9.5 _ 1.5–2.5 cm; surface even, dull, dry, grayish brown to reddish brown (7–8 D/E 3–4), with grayish brown to dark brown (8–9F3–4) fine scabrous squamules; basal tomentum little developed, white to yellowish white. Stipe context solid, orange white (5A2) near the cap to yellowish white (4A2) to greenish white (3B3) at the base, grayish brown to reddish brown (7–8 D/E 3–4) virgate, with scattered brownish gray (8–10E2) or reddish brown (9D4, 9F4–5) encrustations, slowly slightly reddening when cut. Hymenophore tubulose, narrowly adnexed to adnate, subventricose to ventricose, sometimes slightly depressed around the stipe; tubes easily separable, brown to reddish brown (7–8E4–5), 7–15 mm long halfway to the margin, unchanged or slightly reddening when cut; pores 0.4–0.8 mm wide at midradius, mostly roundish, at first dark purple (11F3–4) becoming dark brow to brown (8–9F5–6 to 7F5–6) with age. Odor not observed taste slightly acid. Spore print not observed. Macrochemical reactions: KOH: yellowish then brownish on the cap, stipe, and pileus context; yellowish or greenish on stipe context; yellowish on hymenium. NH4OH: yellowish red on the pileus; yellowish to brownish on pileus context, stipe, stipe context, and hymenium. Basidiospores [168/3/3] (9.3–) 10.2–11.9–14 (–15.5) _ (3.4–)3.9–4.3–5 (–5) mm, Q = (2.18–) 2.4–2.78–3.24 (–3.82). From the type (9.3–) 9.6–11.1–13.1 (–14.1)_(3.4–) 3.8–4.2–4.5 (–4.7) mm, Q = (2.18–) 2.25–2.66–3.44 (–3.82), N = 53, narrowly ellipsoid to subcylindrical with slight of suprahilar depression, thin-walled, smooth, brownish to yellowish hyaline in water, yellowish hyaline in KOH or NH4OH, inamyloid. Basidia 4-spored, (19–) 20–24–28 (–28) _ (9–) 9–10–11 (–11) mm, with sterigmata up to 4 mm long, clavate, hyaline, inamyloid. Cheilocystidia (21–) 21–24–33(–33) _ (4–) 4–6–7 (–7) mm, frequent, mostly cylindrical to fusiform with rounded to tapering apex, thin-walled, hyaline. Pleurocystidia not seen. H. trama divergent to boletoid 30–44 mm wide, with regular to subregular mediostratum 7.5–23 mm wide. Pileipellis an intricate to flattened trichoderm, 85–130 mm thick, made of loosely to moderately interwoven hyphae, thin-walled, mostly hyaline to yellowish pale brown in KOH or NH4OH, with slightly curly cylindrical terminal cells 14–46 _ 3.5–6 mm with rounded apex, with scattered loose crystals. Pileus context made of strongly interwoven hyaline hyphae, 5.5–8.5 mm wide, with scattered loose crystals. Stipitipellis a disrupted palisadoderm, 90–110 mm thick, with clusters of basidiole-like cells 9–25 _ 4–9 mm of thin-walled, mostly hyaline to pale yellowish brown hyphae, subtended by short chains of 3–4 (sub) isodiametric cells, with scattered encrustations. Caulocystidia (18–) 18–25–30 (–30) _ (7–) 7–10–12 (–12) mm, infrequent, fusiform to broadly fusiform, thinwalled, hyaline. Stipe context composed of parallel, 4- to 11-mmwide hyphae, with scattered encrustations. Clamp connections not seen in any tissue. (Fig. 2 F–K; Fig. 3)
Habitat: Solitary or fasciculate on soil, in dipterocarp forest dominated by D. obtusifolius, D. tuberculatus, Sh. obtusa, and Sh. siamensis and a few Hopea sp., as well as Castanopsis spp.
Distribution: Chiang Mai Province, Northern Thailand.
Notes: Sutorius pseudotylopilus is characterized by the following combination of characteristics: medium-sized basidiomata, purplish to reddish brown basidiomata when young; lack of pleurocystidia; pileipellis constituted by an intricate to flattened trichoderm with cylindrical, slightly curly terminal cells with rounded apex. Phylogenetically, the three S. pseudotylopilus specimens formed a clade (clade 4) sister to three undescribed Sutorius species: clade 1 contains three specimens from China (HKAS59657, HKAS52672, and HKAS56291); Sutorius clade 2 contains another specimen from China (HKAS56291), and Sutorius clade 3 contains one specimen (TWO986) from Costa Rica in Central America. The closest described species is S. eximius (American species) in clade 5. However, S. eximius morphologically differs from S. pseudotylopilus by the following characteristics: stipe context unchanging when injured; presence of pleurocystidia (Singer, 1947; Smith and Thiers, 1971; Halling et al., 2012). Moreover, based on our latest phylogenetics analyses with more Sutorius exemplars, we hypothesize that S. eximius is restricted to North. America (clade 5). Additional collections examined: THAILAND: Chiang Mai Province: Mae On District, Ban Huay Kaew community forest, 18_5105600N–99_1702400E, elev. 700 m, June 1, 2017, Santhiti Vadthanarat, SV0401 (CMUB, BR); –ibid., 18_5105500N–99_1702400E, elev. 700 m, May 14, 2018, Santhiti Vadthanarat, SV0415 (CMUB, BR).
Fig. 1 Phylogenetic tree inferred from the three-gene dataset (atp6, rpb2 and tef1), of Sutorius species and selected Boletaceae in Pulveroboletus group, using Maximum Likelihood and Bayesian Inference methods (ML bipartition tree is presented). The three Butyriboletus species were used as outgroup. All generic clades, excluding Sutorius, that were highly supported were collapsed. Seventeen species-level clades within Sutorius are indicated with label. Bootstrap support values (BS 70%) and posterior probabilities (PP 0.90) are shown above the supported branches. The star (*) indicates additional collections with exactly identical sequences or sequences differing only by heteromorphisms in tef1 (with the number of heteromorphisms mentioned in square brackets. (Phylogenetic tree from Vadthanarat et al 2021)