Lactarius rufus (Scop.) Fr.

Barge, Edward G. & Cripps, Cathy L., 2016, New reports, phylogenetic analysis, and a key to Lactarius Pers. in the Greater Yellowstone Ecosystem informed by molecular data, MycoKeys 15, pp. 1-58 : 42-44

Taxon classification Fungi Russulales Russulaceae

22. Lactarius rufus (Scop.) Fr. Figure 24

Description.

Pileus 45-110 mm in diameter, convex to ± depressed–convex to broadly infundibuliform, smooth, at first covered with a fine bloom becoming ± faintly areolate in age, subviscid when wet, becoming dry, azonate, deep red–brown to orange–brown, sometimes with gray–brown bands or blotches; margin incurved when young, becoming straight. Lamellae adnate to subdecurrent, subdistant to crowded, cream to dingy orange–tan in age, discoloring dingy brown where damaged. Stipe 40-90 × 10-15 mm, equal to subclavate, smooth, at first with a fine bloom, dry, cream to tan–pink to red–brown, typically remaining cream toward the base, solid, becoming hollow. Context white to vinaceous–buff. Latex scarce to abundant, white, unchanging. Odor mild. Taste acrid.

Basidiospores 6.8-9.2 × 5.1-7.1 µm, Q = 1.3-1.5, ellipsoid; ornamentation forming a complete reticulum. Pleuromacrocystidia 26-70 × 6-12 µm, scattered to abundant, subfusiform to fusiform; apex obtuse to mucronate. Cheilomacrocystidia 20-50 × 5-9 µm, scattered, subfusiform to fusiform; apex obtuse to broadly acute.

Ecology and distribution.

Widely distributed in the northern hemisphere with conifers and Betula . In the GYE, it occurs in montane mid-elevation mixed lodgepole/spruce-fir forests up through to high elevation mixed lodgepole/spruce-fir/whitebark pine forests, typically on drier, upland sites, summer to fall.

Specimens examined.

U.S.A. MONTANA: Gallatin County, Gallatin Range, Fox Meadow, under Abies lasiocarpa , Picea engelmannii and Pinus albicaulis , 7 Sept 2013, EB125-13 (MONT); Gallatin County, Gallatin Range, Blackmore Trailhead, under Abies lasiocarpa and Pinus contorta , 15 Sept 2015, EB301-15 (MONT); Gallatin County, Gallatin Range, Lick Creek, under Picea engelmannii and Pinus contorta , 27 Aug 2014, EB0076-14 (MONT). WYOMING: Park County, Washburn Range, Dunraven Pass, under Pinus albicaulis and Pinus contorta , 10 Sept 2005, CLC2205 (MONT).

Discussion.

Lactarius rufus appears to be an extremely morphologically and ecologically variable species, although more research is needed to see if this is backed up molecularly. At the ITS region, specimens from the GYE are molecularly identical to European specimens (RPB2 data missing for European collections) (Figure 2C). Similar species in the Rocky Mountains include Lactarius badiosanguineus and Lactarius luculentus v. laetus , both of which are less robust and not acrid.