Butyriboletus pulchriceps (Both, Bessette & R. Chapm.) Kuan Zhao, Zhu L. Yang & Halling, 2015

Butyriboletus pulchriceps (Both, Bessette & R. Chapm.) Kuan Zhao, Zhu L. Yang & Halling View in CoL , comb. nov. Fig. 3a–d View FIGURE 3

MycoBank: MB 812758

Basionym: Boletus pulchriceps Both, Bessette & R. Chapm , North American Boletes, A Color Guide to the Fleshy Pored Mushrooms (Syracuse): 143, 2000

Pileus 8–15 cm in diameter, hemispherical to convex, margin strongly incurved and wavy when young; surface dry, appressed-tomentose but sub-shiny to the naked eye, pale pink over the disc, deeper pink over the marginal areas, fading in age to buff; context pale yellow, deep yellow above tubes, bluing weakly when exposed but soon fading to whitish. Hymenophore surface yellow at first, brownish olive when mature, bluing weakly or unchanging when injured; pores angular, 1–2 per mm; tubes 8–17 mm long, concolorous with the surface, not bluing or only weakly bluing when bruised. Stipe 6.5–7.5 × 1–2 cm, tapered upwards, reticulated over the upper half to two-thirds, the reticulation not strongly raised, with simple, narrow and elongated meshes, the meshes white, the interspaces finely pruinose, yellow near the apex, white with a very pale flush of pink downward; context pale yellow throughout, not bluing when exposed; basal mycelium white. Odor nutty, sweet. Taste not distinct ( Bessette et al. 2000).

Basidiospores [40/1/1] (10) 11–14 × 3–4.5 (5) μm [Q = (2.75) 2.88–3.83 (4.00), Q m =3.31 ± 0.32], subfusiform, subhyaline in KOH. Basidia 24–34 × 6–10 μm, clavate, hyaline in KOH, 4-spored. Hymenophoral trama boletoid. Pleurocystidia 22–40 × 6–8 μm, narrowly lageniform to lageniform, sometimes narrowly clavate, smooth and thin-walled, hyaline in KOH; cheilocystidia 30–44 × 9–13 μm, similar to pleurocystidia in shape. Pileipellis composed of interwoven hyphae 4–6 μm in diameter, smooth, thin-walled, hyaline; end cells not differentiated. Clamp connections absent.

Habitat: Solitary, scattered, or in groups on the ground under oak.

Known distribution: Known from Arizona, southwest of the United States.

Material examined: USA. Arizona, Cochise County, Prope Chiricahua Mountains, Aug 1991, R. Chapman 0945 (BUF, type) .

Notes: Butyriboletus pulchriceps is closely related to Bu. peckii . However, Bu. pulchriceps has a pink to pinkish yellow pileal surface and has no distinctive taste, whereas the pileal surface of Bu. peckii is rose red to deep red and it has a bitter taste (Smith &Theirs 1971; Bessette et al. 2000).

Butyriboletus pulchriceps is similar to Bu. roseopurpureus and B. speciosus . However, the pileal surfaces of the latter two species are bright red or purplish red, not pink to pinkish yellow. Furthermore, the context of Bu. roseopurpureus and B. speciosus will turn blue rapidly and obviously when injured, whereas that of Bu. pulchriceps blues weakly ( Smith & Thiers 1971; Bessette et al. 2000).