Lactarius barrowsii Hesler & A.H. Sm.

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 : 35-36

Taxon classification Fungi Russulales Russulaceae

18. Lactarius barrowsii Hesler & A.H. Sm. Figure 20

Description.

Pileus 30-140 mm in diameter, depressed–convex to broadly infundibuliform, viscid to dry, smooth, azonate, cream to dingy pinkish orange to pale yellow–brown to straw yellow, discoloring red and eventally green in age or where damaged; margin incurved with a white bloom when young, becoming straight to upturned and wavy in age. Lamellae adnate to subdecurrent, crowded to subdistant, dingy pinkish orange to creamy yellow–orange, discoloring red and eventually green where damaged. Stipe 15-50 × 10-30 mm, equal to tapering toward the base, dry, smooth, at first with a white bloom, becoming dingy pinkish orange to yellow–brown in places, staining red and eventually green where damaged, solid, becoming hollow. Context whitish, staining red. Latex scarce to undetectable, watery, red, staining flesh red and eventually green. Odor faintly sweet to spermatic in age. Taste mild.

Basidiospores 8.5-10 × 6-7.5 µm, Q = 1.3-1.5, ellipsoid; ornamentation forming a broken reticulum. Pleuromacrocystidia none observed (absent in Hesler and Smith 1979). Cheilomacrocystidia 30-50 × 2-6 µm, scattered, fusoid; apex acute.

Ecology and distribution.

In Western North America, previously reported with ponderosa and pinyon pine. In the GYE, it occurs in foothills to low montane dry scrubland, so far reported only from under Pinus flexilis , spring and early summer. This is the first report of this species with Pinus flexilis .

Specimens examined.

U.S.A. MONTANA: Gallatin County, Story Hill, under Pinus flexilis , 30 May 2015, EB008-15, EB015-15, EB028-15 (all at MONT); Madison County, Revenue Flats, under Pinus flexilis , 1 June 2015, EB037-15 (MONT).

Discussion.

This is the first report of Lactarius barrowsii from the GYE. Lactarius barrowsii , and other members of section Deliciosi (Fr.:Fr.) Redeuilh, Verbeken & Walleyn, such as Lactarius deliciosus (L.) Gray, Lactarius deterrimus Gröger, and Lactarius rubrilacteus Hesler & A.H. Sm. form a monophyletic group (Figure 2B), previously shown by Nuytinck et al. (2007). Lactarius barrowsii is morphologically close to the western North American Lactarius rubrilacteus . However, in Lactarius barrowsii , the lamellae are more orange, the pileus is lighter and more yellow, the margin has a white bloom when young, and the stipe is often whiter. Phylogenetically, Lactarius barrowsii is very close to the hypogeous, spring fruiting, pine associated Lactarius rubriviridis Desjardin, H.M. Saylor & Thiers, which occurs in similar dry habitats in western North America ( Nuytinck et al. 2007).