Sutorius eximius (Peck) Halling, M. Nuhn & Osmundson, in Halling et al., Mycologia 104(4): 955 (2012)
Pileus 6–15 cm in diam., hemispherical to applanate; surface brown, dark brown to reddish brown, covered with finely matted squamules, dry; context white to pallid, without color change when injured. Hymenophore depressed around apex of stipe; hymenophoral surface purplish pink, brownish pink, purplish red or dark purplish; tubes concolorous with hymenophoral surface; pores angular, 1–3/mm; tubes 6–15 mm long. Stipe 3–12 9 0.8–3 cm, cylindrical, attenuate downwards, pinkish to brownish pink, but much deeper in color downwards, covered with dark purple to blackish squamules; context white to grayish, color unchanging when cut; basal mycelium white. Taste and odor mild.
Basidia 28–50 x 11–15 μm, clavate, 4-spored. Basidiospores (12) 14–15.5 (18) x (4) 4.5–5.5 (6.5) μm, [Q = (2.23) 2.73–3.57 (3.75), Qm = 3.27 ± 0.35], subfusiform in side view, oblong to narrowly ellipsoid in ventral view, yellowish to yellowish brown or pinkish brown, smooth. Hymenophoral trama boletoid; hyphae cylindrical, 3–12 lm wide. Cheilocystidia 26–42 x 5.5–7.5 μm, fusiform to subfusiform or ventricose, usually containing yellowish to brownish pigments, thin-walled. Pleurocystidia similar to cheilocystidia in form but bigger, 40–56 x 10–15 μm. Caulocystidia ventricose, fusoid ventricose, clavate or subfusiform with a sharp apex. Pileipellis a trichodermium composed of yellowish to yellowish brown filamentose hyphae 3–6 μm in width, with terminal cells 31–77 x 3–7.5 μm. Pileal trama composed of interwoven hyphae 7–15 μm wide. Clamp connections absent.
Habit, habitat and distribution: Reported or observed among litter, on soil in forests associated with Dicymbe, Dipterocarpus, Fagus, Hopea, Quercus, Shorea, Tsuga. North America: eastern Canada to Georgia, west to Wisconsin. Costa Rica. Indonesia. Possibly Japan, China and Guyana.
Index Fungorum number: IF563943
Notes: Based on the phylogram, a true S. eximius clade is well supported by molecular data and geography (Java, USA, Costa Rica). The Japanese material was not placed based on molecular inference, but it could be either S. eximius (consistent with other patterns of Laurasian disjunctions) or an Asian group near Sutorius sp. 1 (Thailand). It is not clear where the Guyanan entity would place in a molecular analysis, even though it occurs in northeastern South America, but mycorrhizal partnership with legumes might be consistent with an African grouping near Sutorius sp. 2 (Zambia). Except for variation of spore dimensions (TABLE II), there is little if any morphological difference in the specimens examined. The differences between the Costa Rican and USA measurements probably represent a clinal variation well documented by Halling and Mueller (2002, 2005) and Osmundson and Halling (2010) for many agarics and boletes.
FIgure 1. Phylogenetic relationships and placement of Sutorius eximius within the Boletaceae inferred from a combined nuc-lsu+tef1 dataset (2245 bp) using RAxML and PhyloBayes. The tree topology corresponds to the optimal maximum likelihood tree calculated by RAxML. Support values • 50% BS and 0.95 PP are shown.
Figure 2–4. Sutorius habit images. 2. S. eximius, REH7798, Costa Rica (×1.5). 3. S. eximius, REH8069, Indonesia (×2). 4. S. australiensis, REH9411, Queensland (×1).
Halling R.E., Nuhn M., Fechner N.A., Osmundson T.W., Soytong K., Arora D., Hibbett D.S. 2012. "Sutorius: a new genus for Boletus eximius". Mycologia. 104: 951–61. doi:10.3852/11-376
Wu G, Li YC, Zhu XT, Zhao K, Han LH, Cui YY, Li F, Xu JP, Yang ZL. 2016. One hundred noteworthy boletes from China. Fungal Diversity. 81:25-188