Suillus sect. Diversipedes R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu, 2025

Shi, Xiaofei, Zhang, Shiru, Mueller, Gregory M., Liu, Peigui, Yu, Fuqiang & Senanayake, Indunil C., 2025, A subgeneric revision of the genus Suillus (Suillaceae, Boletales) and novel taxa from Eastern Asia based on morphology and multigene phylogenies, IMA Fungus 16, pp. e 144260-e 144260 : e144260-

Suillus sect. Diversipedes R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu sect. nov.

Etymology.

This section contains a large number of species and is morphologically very diverse. Therefore, the derivation is from diversi - (diverse) and pes (foot).

Diagnosis.

Suillus sect. Diversipedes is distinguished by its striking morphological diversity. Key feature is that sect. Diversipedes form ectomycorrhizal primarily with Pinus (rarely Quercus ). Morphological identifications include: stipes with or without glandular dots (variable in color); partial veil (if present) fibrillose, gelatinous, or membranous; spores olive to cinnamon-brown.

Typification.

Suillus tomentosus Singer, Snell & E. A. Dick , Mycologia 51 (4): 570 (1960) [1959]

Morphology.

Basidiomata stipitate-pileate with tubular hymenophore. Pileus develops from hemispherical to convex, plane or umbonate, sometimes with wavy or recurved margin, viscid to glutinous, or dry, glabrous or covered with fibrils, squamules or scales. Background color ivory to yellow. Some species are covered with pinkish, brown, red or yellow fibrils, appressed squamules or scales. Pileus contains colored scales and glutinous layers yellow, yellowish white, brown, dark brown, olive brown, olive, pinkish, red, or cinnamon. Hymenophore adnate, subdecurrent or decurrent, Pores 1–2 per mm, large ones up to 5 mm diameter, round to angular, radially arranged to almost lamellate. Younger ones of some species beaded with white or yellowish droplets. Sometimes changing color to brownish or light blue when bruised or cut. Context white, whitish yellow, yellow or light orange in pileus and stipe. Stipe context sometimes changing color to blue, greenish blue, reddish or brownish. Stipe equal to clavate, solid, with or without glandular dots, glandular dots whitish, yellow, reddish, brown, or cinnamon brown when young, become cinnamon brown or brown with age. With or without veils, veils often superior, white, pinkish or brownish, persistent or evanescent, fibrillose, cottony, gelatinous, glutinous or membranous. Mycelia always white or pinkish, sometimes changing color to pinkish or red when bruised. Spore print olive, brown, cinnamon brown or olive brown.

Basidiospores smooth, oblong and inequilateral, hyaline yellow to ochraceous brown in KOH, usually 7–11 μm. Basidia 4 - spored, clavate, hyaline yellow in KOH. Cystidia abundant, typically fasciculate, large, up to 100 μm, with brown contents and surrounded by brown amorphous materials in KOH, some species lack caulocystidia. Pileipellis a layer of gelatinous hyphae, with yellowish hyaline content in KOH; some species with a layer of scales that are smooth and light ochraceous in KOH. Clamp connections absent.

Habitat.

Scattered to gregarious, ectomycorrizal with Pinus .

Known species.

Suillus acerbus , S. acidus , S. americanus , S. boletoluteus , S. bovinus , S. cinerescens , S. cothurnatus , S. decipiens , S. discolor (possibly), S. flavidus , S. fuscotomentosus , S. helenae , S. himalayensis , S. hirtellus , S. kwangtungensis , S. megaporinus , S. minusculus , S. phylopictus , S. phylosubaureus , S. pinetorum , S. plorans , S. punctipes , S. salmonicolor , S. sibiricus , S. spraguei , S. subalutaceus , S. subaureus , S. subcinnamomeus , S. subolivaceus , S. subsibiricus , S. suilloides , S. tomentosus , and S. umbonatus .

Notes.

This section is morphologically very diverse. Pileus dry or viscid to glutinous, glabrous or fibrillose to scaly, cap colors variable, colors include yellow, yellowish white, brown, dark brown, olive brown, olive, pinkish, red, and cinnamon. Stipe background color also variable, concolorous or not with pileus. Glandular dots present or not, when present color varies from white, yellow, reddish, brownish. Partial veil present or absent, when present either as appendiculate margin or if an annulus then fibrillose, gelatinous, glutinous or membranous, persistent or evanescent. Spore deposits brown, olive brown, or reddish brown. Hosts of this section include Pinus subgenera Pinus and Strobus . Suillus subaureus is capable of forming association with Quercus .

This section contains numerous potential new or cryptic species. For instance, Suillus cinerescens contains cryptic species with distinct morphological features waiting to be confirmed with more collections. Suillus pinetorum , S. plorans and S. subsibiricus contain geographic cryptic species. An unknown species from Russia, sisters to S. subcinnamomeus is identified in the ITS phylogeny as a potential new species. More species complexes are found in this section compared with other section and subgenera. Resolving species in section Diversipedes requires large sample collections and phylogenetically informative sequences.