Lactarius pubescens 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 : 29

Taxon classification Fungi Russulales Russulaceae

13. Lactarius pubescens Fr. Figure 15

Description.

Pileus 20-100 mm in diameter, depressed–convex to infundibuliform, dry, smooth, hairy toward margin, pale cream to cream or pale pinkish buff; margin bearded, incurved when young becoming straight to wavy in age. Lamellae adnate to decurrent, crowded, pale cream to pale pinkish buff. Stipe 25-50 × 10-15 mm, equal, smooth, dry, pale pinkish buff to pale orange, becoming hollow. Context whitish to pale pinkish buff. Latex not abundant, white, unchanging. Odor fragrant. Taste acrid.

Basidiospores 6-8.5 × 4-6 µm, Q = 1.2-1.5, broadly ellipsoid to ellipsoid; ornamentation forming an incomplete reticulum. Pleuromacrocystidia 25-55 × 7-10 µm, scattered, clavate to fusiform; apex acute to moniliform. Cheilomacrocystidia 25-48 × 5-9 µm, numerous, clavate to fusiform; apex acute to moniliform.

Ecology and distribution.

Originally described from Europe and apparently widespread with Betula and aspen. It also appears to associate with certain herbaceous plants in alpine areas (China) based on publicly available sequences on GenBank isolated from ectomycorrhizal root tips. In the GYE, it occurs with Populus tremuloides and Betula .

Specimens examined.

U.S.A. MONTANA: Deerlodge County, Anaconda Superfund site, under Betula sp., 24 Sept 1996, CLC1045 ( MONT); Park County, Gallatin Range, Cinnabar Basin, under Populus tremuloides , 1992, CLC539 ( MONT); Silver Bow County, 23 Sept 2015, EB300-15 ( MONT).

Discussion.

Morphologically and molecularly (at least at the ITS region), material from the GYE is identical to European material (Figure 2B). In North America, Hesler and Smith (1979) distinguish an Lactarius pubescens v. betulae (A.H. Sm.) Hesler & A.H. Sm. based on yellowing latex among other subtle features, however yellowing latex was not noted in our collections. Further investigation of Lactarius pubescens in North America is warranted. The Betula associate Lactarius torminosus is similar, and closely related (Figure 2B) but its basidiomes are typically more pink colored and it has larger basidiospores (7.5-9.6 × 5.6-6.9 µm) ( Heilmann-Clausen et al. 1998). Lactarius resimus (Fr.) Fr. is also similar, however it has strongly yellowing latex and flesh and larger basidiospores (7.0-9.7 × 5.3-7.2 µm) ( Heilmann-Clausen et al. 1998). See comments under Lactarius pseudodelicatus for distinguishing features for that taxon.