The North American Suillus cavipes:
Summarizing our results, we consider: (i) S. neoalbidipes M.E. Palm & E.L. Stewart a synonym of S. glandulosipes Thiers & A.H. Sm.; (ii) S. borealis A.H. Sm. Thiers & O.K. Miller is a synonym of S. brunnescens A.H. Sm. & Thiers; (iii) Boletus serotinus Frost and Boletus solidipes Peck synonyms of Suillus elbensis (Peck) Kuntze; (iv) S. lactifluus (With.) A.H. Sm. & Thiers a synonym of S. granulatus (L.) Roussel; and (v) S. himalayensis B. Verma & M.S. Reddy a synonym of S. americanus (Peck) Snell. Further, we propose usage of the names: (xi) S. clintonianus in the place of the North American S. grevillei; (xii) S. ampliporus in the place of the North American S. cavipes; (xiii) S. elbensis in place of the North American S. viscidus; and (xiv) S. weaverae in place of the North American S. granulatus.
Nguyen, et al.1(boldface added).
1 Nhu H. Nguyen, Else C. Vellinga, Thomas D. Bruns & Peter G. Kennedy (2016). Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa, Mycologia 108:6, 1216-1228 (also available via ResearchGate)
To quote Nguyen et al. Mycologia October 2016: 16-106:
“The /cavipes clade contained species that are mostly well defined morphologically and well supported by phylogeny (FIG. 1A). Suillus cavipes (Opat.) A.H. Sm. & Thiers itself may be separated into two species, one from Eurasia and the other from North America. It was originally described as Boletus cavipes Opat. from subalpine habitats in Styria, Austria (Opatowski 1836). Therefore, the name is best applied to the European/Asian clade. The name Suillus ampliporus (Peck) Kuntze is available for the North American taxon. Index Fungorum (www.indexfungorum.org) erroneously lists Boletinus porosus (Berk.) Peck as a synonym of S. cavipes, but that species is considered a synonym of Boletinellus merulioides (Schwein.) Murrill