Pileus 8–20 mm in diameter (to 80 mm in Hesler and Smith 1979), plano-convex to infundibuliform, ± papillate, dry, finely rimulose to minutely squamulose, red-brown to orange-brown to pinkish cinnamon; margin finely crenulate, incurved when young, becoming straight to wavy in age. Lamellae adnate to subdecurrent, subdistant to crowded, cream to creamy tan, discoloring slightly darker where damaged. Stipe 8–23 × 5–8 mm (30–50 × 10–15 mm in Hesler and Smith 1979), equal to slightly clavate, smooth, dry, pale creamy yellow to creamy tan, solid, becoming hollow. Context concolorous with pileus. Latex scarce, watery, white, unchanging. Odor mild. Taste mild.

Basidiospores 7–9.5 × 5–7.5 µm, Q = 1.3–1.5, ellipsoid; ornamentation forming a broken to partial reticulum. Pleuromacrocystidia 60–100 × 6–10 µm, numerous, strongly projecting, mucronate to fusoid; apex acute to moniliform. Cheilomacrocystidia 50–80 × 6–10 µm, numerous, strongly projecting, mucronate to fusoid; apex acute to moniliform.

In western and into eastern North America with Alnus. In the GYE only one collection has been made thus far and it was from a riparian area near Alnus incana and Populus trichocarpa, late summer. Further sampling under Alnus in the Rocky Mountains is necessary.

U.S.A. MONTANA: Carbon County, Red Lodge, along Rock Creek, under Alnus incana and Populus trichocarpa, 6 Sept 2015, EB161-15 (MONT).

This is the first report of L. alpinus v. mitis from the GYE. According to Hesler and Smith (1979), L. alpinus v. mitis has duller pileus and lamellae colors than L. alpinus v. alpinus Peck, which typically develops bright yellow to apricot colors; variety mitis also has longer and more conspicuous macrocystidia and a mild rather than slowly acrid taste. The collection described here likely did not reach full maturity, and the basidiomes are smaller than reported in Hesler and Smith (1979). Phylogenetic analyses including material of L. alpinus v. alpinus from near the type locality suggest that L. alpinus v. mitis and L. alpinus v. alpinus are distinct species (Figure 2A, 2C), however a more in depth analysis incorporating type material of at least L. alpinus v. mitis should be carried out before making this determination final. For an interesting discussion on L. alpinus see Nuytinck and Voitk (2016) and Rochet et al. (2011).

While L. alpinus v. mitis appears to be quite distantly related to L. alpinus v. alpinus, it is very closely related to the European L. lilacinus (Lasch) Fr., the recently described Mexican L. cuspidoaurantiacus Montoya, Bandala & Garay-Serr., and to a lesser extent L. lepidotus Hesler & A.H. Sm., all of which are also associated with Alnus (Figure 2A). Lactarius lilacinus is typically more pink to violet in color and has a fruity smell. Lactarius cuspidoaurantiacus appears to have more yellow-orange basidiomes, more orange colored, distant lamellae, and a Pelargonium-like odor (Montoya et al. 2014). Lactarius lepidotus has a more gray-brown to beige pileus. Neither L. lilacinus, L. cuspidoaurantiacus or L. lepidotus have been reported from the Rocky Mountains.

Figure 3. 

Lactarius alpinus v. mitis. Top collection EB161-15 under Alnus incana and Populus trichocarpa, Red Lodge, Montana, USA. Bottom collection EB516-15 under Alnus rubra, western Oregon, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 10–50 mm in diameter, shallowly convex to plano-convex becoming plane to infundibuliform, ± papillate, smooth, slightly viscid to dry, with whitish glaucous coating when immature, easily rubbing away or fading in age, deep brown to gray-brown to liver brown with lighter and darker areas present, often lighter toward margin, becoming lighter overall upon desiccation; margin straight when young becoming upturned and wavy to convoluted in age. Lamellae adnate to subdecurrent, subdistant, cream when immature becoming dingy cream to light tan in age, sometimes with a faint pinkish tinge, discoloring to dingy tan where damaged. Stipe 5–30 × 3–15 mm, equal to clavate, central, smooth, dry, at first covered with whitish glaucous coating as in pileus, pale apricot to dingy cream-tan, hollow. Context dingy cream to brownish. Latex scarce to undetectable, watery, white, unchanging. Odor mild. Taste mild to slightly acrid.

Basidiospores 7–10.5(–12) × 5–8 µm, Q = 1.1–1.6, subglobose to ellipsoid; ornamentation forming an incomplete reticulum. Pleuromacrocystidia 53–96.5(–114) × 6.5–11.5 µm, scattered to abundant, lanceolate; apex acute to moniliform. Cheilomacrocystidia 26–91.5 × 7.5–10 µm, scattered to abundant, subulate to linear; apex acute to rounded.

Widespread in arctic-alpine areas in the Northern Hemisphere with Salix. In the GYE and elsewhere in the Rocky Mountains it occurs above tree line in alpine areas with Salix arctica, S. reticulata, and S. planifolia, late summer.

U.S.A. MONTANA: Carbon County, Beartooth Plateau, Highline Trail, among shrubby and dwarf Salix, 7 Aug 1998, CLC1221 (MONT); among Salix reticulata and other Salix spp., 8 Aug 1998, ZT6422 (MONT); among Salix arctica, S. planifolia and S. reticulata, 18 Aug 2013, EB106-13 (MONT). WYOMING: Park County, Beartooth Plateau, Frozen Lakes, among Salix arctica, 21 Aug 1999, CLC1403 (MONT); Park County, Beartooth Plateau, Solifluction Terraces, among Salix arctica, S. planifolia and S. reticulata, 11 Aug 2012, EB125 (MONT).

L. nanus is morphologically and phylogenetically close to L. hysginoides Korhonen & T. Ulvinen (Figure 2A), however, the latter has a more cinnamon-toned pileus, smaller basidiospores (6.5–8.5 × 4.9–7.1 µm), and occurs in boreal areas with Betula, Picea and Salix; it has not been reported from the Rocky Mountains. Lactarius pallidomarginatus Barge and C.L. Cripps is also similar, however, it is a violet staining species. Differences between L. nanus and L. glyciosmus (Fr.) Fr. are discussed in the comments section under the latter.

Figure 4. 

Lactarius nanus. Collection EB106-13 near Salix arctica (pictured), S. reticulata, and S. planifolia, Beartooth Plateau, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 15–50 mm in diameter, broadly convex, later becoming plane with or without a depressed center and small papilla, smooth, dry, azonate to lightly zoned especially near the margin, pale gray-brown to violet-brown with a whitish glaucous coating when immature, fading in age; margin incurved when young and remaining so or becoming straight in age. Lamellae adnate to subdecurrent, subdistant to crowded, cream to pale pinkish to pale yellow-orange. Stipe 10–40 × 3–12 mm, equal to slightly clavate, central to eccentric, smooth, dry, buff or pale salmon with a faint glaucous coating at first as in pileus, stuffed, becoming hollow, often white-mycelioid toward the base. Context pale cream. Latex scarce to undetectable, watery, white, unchanging. Odor of coconut. Taste mild to slightly acrid.

Basidiospores 7–9 × 5–7 µm, Q = 1.2–1.4, broadly ellipsoid to ellipsoid, ornamentation forming an incomplete to nearly complete reticulum. Pleuromacrocystidia 45.5–63.5 × 6.5–7.5 µm, scarce to scattered, subclavate to lanceolate; apex rounded to mucronate. Cheilomacrocystidia 33–66 × 5–9 µm, scattered to abundant, cylindrical to subclavate; apex rounded.

Widespread in the Northern Hemisphere in temperate, boreal, and arctic-alpine areas with Betula. In the GYE and elsewhere in the Rocky Mountains, it occurs in subalpine and alpine areas with Betula glandulosa and possibly other Betula spp., late summer.

U.S.A. MONTANA: Carbon County, Beartooth Plateau, Birch Site, near Betula glandulosa, 29 July 1997, CLC1134 = ZT6096 (MONT); 8 Aug 1998, CLC1217 (MONT); 10 Aug 1999, TWO269 (MONT); 19 Aug 1999, CLC1380 (MONT); 13 Aug 2007, ZT12723 (MONT); Carbon County, Hellroaring Plateau, Hellroaring Creek, near Betula glandulosa, 9 Aug 2015, EB111-15 (MONT). WYOMING: Park County, Beartooth Plateau, Island Lake, near Betula glandulosa, 6 Sept 2015, EB160-15 (MONT).

Lactarius glyciosmus is very closely related to L. mammosus Fr. (Figure 2A), however, the latter has a browner pileus, stouter stature, and ecology with Pinaceae (although it has been reported with Betula) (Heilmann-Clausen et al. 1998). Lactarius vietus (Fr.) Fr. has a distinct pale zone near the stipe apex, latex that dries greenish gray, longer pleuromacrocystidia (50–90 × 7–12 µm), a mild to slightly fruity odor, and a strongly acrid taste (Heilmann-Clausen et al. 1998). The presence of L. mammosus and L. vietus in the Rocky Mountains is unclear. Lactarius trivialis (Fr.) Fr., which has been reported from the GYE (McKnight 1982), but could not be confirmed, is typically larger with slightly larger basidiospores (7.3–10 × 5.9–7.8 µm), more numerous pleuromacrocystidia, and a mild to acidic-fruity odor (Heilmann-Clausen et al. 1998). Lactarius nanus has larger basidiospores (7–10.5(–12) × 5–8 µm), larger and differently shaped pleuromacrocystidia (53–96.5(–114) × 6.5–11.5 µm), a mild odor, and associates with Salix.

Figure 5. 

Lactarius glyciosmus. Collection EB111-15 under Betula glandulosa, Hellroaring Plateau, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 60–100 mm in diameter, convex to plano-convex usually with a depressed center and sometimes with a papilla, smooth at center, becoming increasingly hairy to bearded toward margin, viscid to dry, azonate, surface orange-brown at center, becoming pale yellow-brown to cream toward margin; hairs pale yellow-brown to red-brown; margin strongly incurved, remaining so or becoming nearly straight in age. Lamellae adnate to decurrent, crowded, cream to pale-yellow, staining violet where damaged. Stipe 30–70 × 15–35 mm, stout, equal to clavate, viscid to dry, cream to pale-yellow, often with numerous dingy yellow, golden yellow, yellow-brown, or light orange-brown scrobicules, hollow. Context white, staining violet where damaged. Latex scarce to abundant, white, becoming violet. Odor spicy-floral, resinous. Taste resinous to slightly acrid.

Basidiospores 8–10.5 × 6–8.5 µm, Q = 1.1–1.4, broadly ellipsoid to ellipsoid; ornamentation forming an incomplete to dense reticulum. Pleuromacrocystidia 78.5–145 × 9–13 µm, scattered to abundant, strongly projecting, subfusiform to lanceolate; apex acute to moniliform. Cheilomacrocystidia 56–140 × 7.5–13 µm, scattered to abundant, strongly projecting, subfusiform to lanceolate; apex acute moniliform.

Widespread in the Northern Hemisphere in temperate, boreal, and arctic-alpine areas with Picea, Betula, and possibly Salix. In the GYE, it occurs in the spruce-fir and krummholz zone, typically near Salix glauca and Picea engelmannii, sometimes also intermixed with Arctostaphylos uva-ursi and Betula glandulosa, late summer.

U.S.A. MONTANA: Carbon County, Beartooth Plateau, Birch Site, among Salix glauca and krummholz Picea engelmannii, 12 Aug 2002, CLC1971 (MONT); 13 Aug 2007, CLC2318 (MONT); 18 Aug 2013, EB107-13 (MONT); Carbon County, Hellroaring Plateau, Hellroaring Creek, among Arctostaphylos uva-ursi, Salix glauca and krummholz Picea engelmannii, 9 Aug 2015, EB116-15 (MONT). WYOMING: Park County, Beartooth Plateau, Frozen Lakes, among Salix glauca and krummholz Picea engelmannii, 21 Aug 1999, CLC1394 (MONT).

Due to its conspicuously bearded margin, and violet staining tissue, L. repraesentaneus is difficult to confuse with anything else in the Rocky Mountains. It is very closely related to the arctic-alpine Dryas and Salix associate L. dryadophilus Kühner (Figure 2A), however, the latter features a cream to yellow, smoother pileus with hairs restricted to near the margin, and a basidiospore ornamentation consisting of sparse, thinner ridges (Heilmann-Clausen et al. 1998). Lactarius dryadophilus has not been reported from the Rocky Mountains. Lactarius repraesentaneus and other violet-staining species such as L. uvidus (Fr.) Fr., L. aspideus (Fr.) Fr., L. salicis-reticulatae Kühner, L. montanus (Hesler & A.H. Sm.) Montoya & Bandala, L. pallidomarginatus, and L. brunneoviolaceus M.P. Christ., etc. occur together in a weakly supported clade, that corresponds with section Uvidi (Konr.) Bon (Figure 2A).

Figure 6. 

Lactarius repraesentaneus. Collection EB107-13 near krummholz Picea engelmannii and Salix glauca, Beartooth Plateau, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 20–40 mm in diameter, convex to broadly convex, usually with a depressed center, smooth, viscid to dry, azonate, cream, pale yellow, or pale ocher, sometimes darker toward the center, staining violet where damaged; margin incurved, remaining so or becoming merely downturned in age. Lamellae adnate to subdecurrent, subdistant to distant, cream, pale yellow, or pale orange-ocher often with a pinkish-buff tint, staining violet where damaged. Stipe 15–20 × 10–15 mm, equal to clavate, viscid to dry, cream to pale-yellow, staining violet where damaged, hollow. Context white, staining violet where damaged. Latex scarce to undetectable, watery, white, becoming violet. Odor mild to slightly sweet. Taste mild.

Basidiospores (7–)8.5–11.5 × (7–)8–10 µm, Q = (1–)1.1–1.4, subglobose to ellipsoid; ornamentation forming an incomplete reticulum. Pleuromacrocystidia 76–101.5 × 7.5–11.5 µm, scarce, strongly projecting, subfusiform to fusiform; apex rounded to acute to moniliform. Cheilomacrocystidia 68.5–91.5 × 7.5–10.5 µm, scattered to abundant, strongly projecting, subfusiform to fusiform; apex acute to rounded to moniliform.

Widespread in arctic-alpine areas in the Northern Hemisphere with Salix. In the GYE, it occurs in alpine areas with S. arctica, S. reticulata, as well as shrubby Salix spp., sometimes also intermixed with Dryas octopetala, late summer.

U.S.A. MONTANA: Carbon County, Beartooth Plateau, Birch Site, among Salix reticulata, 17 Aug 2011, CLC2776 (MONT); Carbon County, Beartooth Plateau, Highline Trail, among dwarf Salix spp., 8 Aug 1998, CLC1211 (MONT); Carbon County, Hellroaring Plateau, Hellroaring Creek, under shrubby Salix sp., 8 Aug 2015, EB112-15 (MONT); among shrubby Salix sp. and S. reticulata, 8 Aug 2015, EB113-15 (MONT); among Dryas octopetala, shrubby Salix sp. and S. reticulata, 8 Aug 2015, EB117-15 (MONT), EB118-15 (MONT), EB119-15 (MONT); Sweet Grass County, Crazy Mountains, above Blue and Granite Lakes, among Salix arctica, 1 Aug 2015, EB101-15 (MONT). WYOMING: Park County, Beartooth Plateau, Gardner Lake, under shrubby Salix sp., 16 Aug 2014, EB0057-14 (MONT).

Lactarius aspideoides Burl., described from eastern North America is closely related (Figure 2A), however, it is generally larger, with a somewhat zonate pileus. It also has more crowded lamellae that lack salmon-colored hues, slightly smaller basidiospores (7–10 × 7–8–µm) with broader ridges, a bitter to slightly acrid taste, and a subalpine ecology (Hesler and Smith 1979). The status of L. aspideoides in western North America is unclear. Lactarius aspideus, another similar species which was described from northern Europe with Salix, has smaller basidiospores (6.7–9.5 × 5.6–7.8 µm) with denser reticulation, more crowded, creamier colored lamellae, and a habitat mainly in subalpine areas (Heilmann-Clausen et al. 1998). The presence of L. aspideus in North America is unclear. Lactarius salicis-herbaceae Kühner, a closely related (Figure 2A) arctic-alpine Salix associate, which has not been reported from the Rocky Mountains, has darker yellow to yellow-brown sporocarps, pale cream to grayish buff lamellae, and more densely reticulate basidiospores (Heilmann-Clausen et al. 1998).

Figure 7. 

Lactarius salicis-reticulatae. Collection EB0057-14 under shrubby Salix sp., Beartooth Plateau, Wyoming, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 20–50 mm in diameter, convex to broadly convex to plane with or without a depressed center, smooth, subviscid to dry, azonate, blotchy light tan to light brown, developing violet stains, lighter (to cream) toward margin; margin incurved when young, remaining so or becoming nearly straight in age. Lamellae adnate to subdecurrent, subdistant to slightly crowded, white to pale yellow-cream, staining violet where damaged. Stipe 10–40 × 5–10 mm, equal to slightly clavate, smooth, dry, white to cream, staining violet where damaged, hollow. Context white to cream, staining violet where damaged. Latex scarce to undetectable, watery, white, staining tissue violet. Odor mild. Taste mild.

Basidiospores 8–10 × 6.5–8 µm, Q = 1.1–1.4, broadly ellipsoid to ellipsoid; ornamentation forming an incomplete to dense reticulum. Pleuromacrocystidia 81.5–112 × 9–10 µm, scarce to scattered, cylindrical to lanceolate; apex acute to moniliform. Cheilomacrocystidia 48–101.5 × 7.5–13 µm, scattered, cylindrical to lanceolate; apex acute to moniliform.

Known from only a few alpine localities in the central and southern Rocky Mountains with Salix planifolia and possibly also S. glauca, late summer.

U.S.A. WYOMING: Sublette County, Wind River Range, Union Peak, near Salix glauca, 22 Aug 1994, ZT5229 (MONT).

This species was recently described (Barge et al. 2016) from the alpine zone in Southern Colorado with Salix. It is tentatively included here because a collection morphologically matching the type was made by Dr Egon Horak from the Wind River Range of Wyoming (technically in the southern GYE) with Salix glauca. Interestingly, out of all of the species examined thus far, L. pallidomarginatus appears most closely related to the bright yellow, violet-staining Salix associate L. aspideus (Figure 2A), to which it bares little resemblance.

In the Rocky Mountains, L. pallidomarginatus is most easily confused with L. nanus, L. glyciosmus, L. montanus, and L. aff. brunneoviolaceus. The basidiomes of L. nanus do not stain violet where damaged and it produces basidiospores with thicker, more jagged ridges, and macrocystidia with more rounded apices (see Barge et al. 2016). Lactarius glyciosmus also does not stain violet where damaged, it has an odor of coconut, slightly smaller basidiospores (7–9 × 5–7 µm), and smaller cheilomacrocystidia (33–66 × 5–9 µm). The closely related violet-staining L. montanus produces basidiomes which are typically much more robust and stain green on the stipe and pileus surface with KOH. Lactarius montanus also has a strongly resinous odor and taste, and is mainly subalpine with conifers. See comments under L. aff. brunneoviolaceus for features differentiating L. pallidomarginatus from that taxon. See Barge et al. (2016) for features differentiating L. pallidomarginatus from the European taxon L. pseudouvidus Kühner.

Figure 8. 

Lactarius pallidomarginatus. Collection EB0041 under Salix planifolia, San Juan Mountains, Colorado, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 30–100 mm in diameter, convex to ± depressed–convex to infundibuliform, viscid, smooth, azonate to zonate, zones consisting of darker spots arranged concentrically, gray–brown to vinaceous–gray to violet–brown; margin straight to slightly incurved when young, becoming straight and ± wavy. KOH on pileus cuticle and stipe green. Lamellae adnate to subdecurrent, crowded to subdistant, cream, discoloring violet where damaged with rust brown stains also often present on older material. Stipe 30–70 × 10–30 mm, equal to clavate, smooth with light tomentum often present especially toward base, dry, white to light brown, discoloring violet and eventually rust brown where damaged, solid, becoming hollow. Context white, discoloring violet and eventually rust brown where damaged. Latex scarce to copious, white, staining tissue violet. Odor strongly resinous. Taste strongly resinous.

Basidiospores 7–10.5 × 6–8 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a broken to partial reticulum. Pleuromacrocystidia 50–90 × 5–10 µm scarce to scattered, fusoid–acuminate; apex acute to moniliform. Cheilomacrocystidia 30–55 × 4–9 µm, scarce, fusoid–acuminate; apex acute to moniliform.

Under conifers in western North America. In the GYE, it occurs in wet areas, often along streams in the montane spruce-fir and krummholz zones, possibly always in the presence of Picea engelmannii, summer and fall.

U.S.A. MONTANA: Madison County, Madison Range, Mirror Lake, swampy area under Abies lasiocarpa and Picea engelmannii. 3 Sept 2013, EB120-13 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Picea engelmannii and Salix planifolia, 31 Aug 2013, CLC3001 (MONT), under Picea engelmannii, 1 Sept 2014, EB0071-14 (MONT), EB0072-14 (MONT), EB0073-14 (MONT).

In western North America, similar species with violet-staining flesh include L. pallescens Hesler & A.H. Sm., L. californiensis Hesler & A.H. Sm., and L. cordovaensis Hesler & A.H. Sm. Lactarius pallescens and L. californiensis are generally more white overall in color, have a slightly acrid to acrid taste (not strongly resinous), and do not stain green in KOH. Lactarius cordovaensis has orange–tan lamellae when young, and possibly slightly smaller basidiospores (7.5–9.5 × 6.5–8 µm). Lactarius uvidus, a European species whose presence has not been confirmed molecularly for North America, typically has a lighter pileus, a bitter taste (not strongly resinous), and does not stain green in KOH. Previous reports of L. uvidus from the GYE (McKnight 1982) and the Central and Southern Rocky Mountains in general likely refer to L. montanus. See comments under L. aff. brunneoviolaceus and L. pallidomarginatus for features differentiating L. montanus from those taxa.

Figure 9. 

Lactarius montanus. Top collection EB0072-14 and bottom collection EB0073-14 under Picea engelmannii, Tobacco Root Mountains, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 30–60 mm in diameter, convex to slightly depressed–convex, smooth, viscid, faintly zonate, brownish with lavender hues, marbled, whitish near margin; margin incurved and faintly tomentose when young. KOH on pileus cuticle green. Lamellae adnate, crowded, cream, staining violet where damaged. Stipe 25–30 × 20–25 mm, clavate, smooth, white with hoary coating, staining violet where damaged, hollow. Context not observed. Latex white, unchanging, staining tissue violet. Odor sweet. Taste mild, becoming slightly bitter.

Basidiospores 8–12 × 6.5–8 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming an incomplete reticulum. Pleuromacrocystidia 40–90 × 8–12 µm, scattered to numerous, subfusiform to fusiform; apex mucronate. Cheilomacrocystidia 40–88 × 7–12 µm, numerous, fusiform; apex mucronate.

Lactarius brunneoviolaceus occurs in arctic-alpine areas with Salix. The species described here was found growing near tree line (krummholz spruce present) on the Beartooth Plateau amongst Salix reticulata and S. planifolia, late summer.

U.S.A. MONTANA: Custer County, Beartooth Plateau, Birch Site, among krummholz Picea engelmannii, Salix reticulata and Salix planifolia, 15 Aug 2014, CLC3098 (MONT).

More collections and molecular data from this species are needed, however, this is the first report of a species from the GYE, and to the best of our knowledge, North America, bearing affinities to the arctic-alpine Salix associate L. brunneoviolaceus. Unfortunately, high quality sequence data was not obtained for this collection, and only a small portion of ITS1 could be used for phylogenetic analyses, which placed it with L. brunneoviolaceus. Morphologically, it is also a close match, except that the pileus of the species described here stains green with KOH, which is not historically mentioned for L. brunneoviolaceus. It is possible that the pileus of L. brunneoviolaceus stains green in KOH as well but that it has not been thoroughly tested. In CLC2133 from Norway, another specimen closely matching L. brunneoviolaceus which was examined, the pileus (of dried material) also stained green in KOH.

This species is very closely related to L. montanus (Figure 2A), however, the latter features slightly smaller basidiospores (7–10.5 × 6–8 µm, although sometimes to 12 µm long), and is typically below tree line with conifers. Lactarius pallidomarginatus, which is also closely related, has lighter colored, less violaceous pilei that do not stain green in KOH, and smaller basidiospores (8–10 × 6.5–8 µm).

Figure 10. 

Lactarius aff. brunneoviolaceus. Collection CLC3098 near Salix reticulata (pictured), S. planifolia, and krummholz Picea engelmannii, Beartooth Plateau, Montana, USA. Scale bar: 2 cm. Photo by C. Cripps.

Pileus 35–100 µm in diameter, convex to broadly convex to nearly plane, ± centrally depressed, viscid to dry, smooth, more or less azonate, cream to pale gray–brown to pale vinaceous–brown, ± discoloring ochraceous in places; margin incurved when young, becoming straight in age. Lamellae adnate to subdecurrent, crowded to subdistant, white at first, becoming pale creamy buff, ± discoloring ochraceous to brown where damaged. Stipe 30–80 × 10–35 mm, equal to clavate, viscid to dry, smooth, white, developing ochraceous to faintly violet areas where damaged, solid, becoming hollow. Context white. Latex scarce to undetectable, white, unchanging. Odor mild. Taste acrid.

Basidiospores 8–12 × 7–9 µm, Q = 1.2–1.4, broadly ellipsoid to ellipsoid; ornamentation forming a broken to partial reticulum. Pleuromacrocystidia 50–110 × 8–12 µm, scattered to numerous, subcylindric to fusoid; apex rounded to acute. Cheilomacrocystidia 40–60 × 8–12 µm, scattered to abundant, clavate to mucronate; apex rounded to acute.

In mountainous areas in western North America with conifers. Hesler and Smith (1979) report it as the common montane Lactarius of wet places in the spruce-fir zone of the Rocky Mountains during the summer and early fall. In the GYE, it occurs in wet depressions and near seeps as well as in drier upland sites in the montane spruce-fir zone, possibly always in the presence of Abies lasiocarpa, summer to fall.

U.S.A. MONTANA: Gallatin County, Gallatin Range, East Fork Hyalite Creek, under Abies lasiocarpa and Picea engelmannii, 25 Aug 2015, EB158-15 (MONT); Gallatin County, Gallatin Range, Windy Pass Trail, under Abies lasiocarpa and Pinus contorta, 10 Aug 2013, EB102-13 (MONT); Madison County, Madison Range, Big Sky, under Abies lasiocarpa, Picea engelmannii and Pinus albicaulis, 4 Sept 2004, CLC2052 (MONT); Madison County, Madison Range, Mirror Lake, under Abies lasiocarpa, 3 Sept 2013, EB121-13 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Abies lasiocarpa, 1 Sept 2014, EB0074-14 (MONT); Sweet Grass County, Crazy Mountains, Big Timber Creek, under Abies lasiocarpa and Picea engelmannii, 1 Aug 2015, EB095-15 (MONT). WYOMING: Park County, Beartooth Plateau, Beartooth Lake Campground, under Abies lasiocarpa and Picea engelmannii, 5 Sept 2015, EB159-15 (MONT).

The European Abies associate L. albocarneus Britzelm. appears to be closely related (Figure 2B), however, it has a lighter cream to dingy whitish pileus, and slowly yellowing latex and flesh (Heilmann-Clausen et al. 1998). The western North American L. kauffmanii Hesler & A.H. Sm. and L. pseudomucidus Hesler & A.H. Sm. also appear to be related (Figure 2B). Lactarius kauffmanii has a dark to blackish brown pileus (although it can be lighter), smaller basidiospores (7–10 × 6.5–8 µm), and a vinaceous to tan stipe. Lactarius pseudomucidus typically has a darker and more slimy pileus, a gray to gray–brown stipe, and smaller basidiospores (7–9 × 6–7 µm). Both L. kauffmanii and L. pseudomucidus may be confined to Douglas fir/western hemlock forests of the Pacific Northwest (Hesler and Smith 1979). The western North American L. circellatus v. borealis Hesler & A.H. Sm. is also similar, however, its pileus is pruinose at first and generally darker and faintly zonate to zonate, it has a dry stipe (never viscid as in L. caespitosus), and its lamellae are unstaining when cut (Hesler and Smith 1979, Methven 1997). Lactarius trivialis is also similar, however it appears to be fairly distantly related (Figure 2A); it has purplish gray to vinaceous colors of the pileus at least when young and smaller basidiospores (7.3–10 × 5.9–7.8 µm) (Heilmann-Clausen et al. 1998). Lactarius argillaceifolius Hesler & A.H. Sm. and its varieties are also similar, however, all feature a more purplish gray pileus at least when young (similar to L. trivialis) and smaller basidiospores. Variety argillaceifolius appears to be confined to oak forests in central and eastern North America, v. megacarpus Hesler & A.H. Sm. to oak forests in coastal western North America, and v. dissimilis Hesler & A.H. Sm. is represented by only one collection from South Carolina (Hesler and Smith 1979).

Figure 11. 

Lactarius caespitosus. Top collection EB0074-14 under Abies lasiocarpa, Tobacco Root Mountains, Montana, USA. Bottom collection EB095-15 under Abies lasiocarpa and Picea engelmannii, Crazy Mountains, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 50–120 mm in diameter, depressed–convex to infundibuliform, smooth, viscid to dry, faintly zonate, zones narrow and often more conspicuous near the margin, cream to pale tan–cream, often with tan to rust brown blotches; margin incurved and faintly short–tomentose when young, becoming glabrous and straight to undulating in age. Lamellae adnate to subdecurrent, crowded, creamy pink to pink–tan, discoloring tawny light brown where damaged. Stipe 25–50 × 17–28 mm, short, equal to tapering toward the base, subviscid to dry, smooth, ± scrobiculate, white, discoloring pale yellow to tawny light brown where damaged, solid, becoming hollow. Context white, discoloring tawny light brown. Latex scarce, white, unchanging. Odor faint to slightly spermatic. Taste slowly acrid.

Basidiospores 5.5–8 × 4.5–5.5 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a nearly complete reticulum. Pleuromacrocystidia 25–50 × 3–7 µm, scarce, cylindric to fusiform; apex acute to moniliform. Cheilomacrocystidia 25–40 × 3–6 µm, scarce, cylindric to fusiform; apex rounded to acute.

Widely distributed in the northern hemisphere with Populus (aspen), Salix, and possibly Betula. In the GYE it occurs in montane areas near Populus tremuloides, summer and fall.

U.S.A. IDAHO: Teton County, Teton Mountains, under Populus tremuloides, CLC290 (MONT). MONTANA: Carbon County, near Red Lodge, along Rock Creek, under Populus tremuloides, 8 Aug 2015, EB110-15 (MONT); Park County, Cinnabar Basin, under Populus tremuloides, 18 July 1990, CLC106 (MONT), 2 Aug 1990, CLC116 (MONT), 11 Sept 1991, CLC262 (MONT), 13 July 1992, CLC462 (MONT); Silverbow County, Butte, East Ridge, under Populus tremuloides, 15 Aug 1993, CLC699 (MONT). WYOMING: Park County, along Beartooth Highway, under Populus tremuloides, 16 Aug 2014, EB0061-14 (MONT).

L. controversus is fairly easily recognized by its small basidiospores, whitish pileus, pinkish lamellae, acrid taste, and association with aspen. No other species is similar in the Rocky Mountains. While morphological differences between European and GYE material were not detected, there is some molecular divergence, which could indicate separate species, although more material needs to be examined (Figure 2B).

Figure 12. 

Lactarius controversus. Collection EB110-15 under Populus tremuloides, Beartooth Mountains, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 20–100 mm in diameter, depressed–convex to infundibuliform, smooth, viscid, zonate, color alternating between rich and dull orange; margin incurved when young becoming straight to wavy in age. Lamellae adnate, crowded to subdistant, cream to dingy yellow, staining orange–brown in age or where damaged. Stipe 20–50 × 10–25 mm, equal to tapering toward the base, smooth, white, at first with a white bloom, staining dingy orange–brown where damaged, solid, becoming hollow. Context white. Latex white, unchanging, staining lamellae orange–brown. Odor mild. Taste acrid.

Basidiospores 8–11.5 × 7.5–9.5 µm, Q = 1.1–1.3, broadly ellipsoid; ornamentation forming a broken to nearly complete reticulum. Pleuromacrocystidia 20–50 × 3–6 µm, scattered to numerous, fusiform; apex acute to moniliform. Cheilomacrocystidia 20–35 × 3–6 µm, scattered, fusiform; apex acute to moniliform.

In montane conifer forests in western North America. In the GYE, it occurs in seeps and along streams in the spruce-fir zone possibly always in the presence of Picea engelmannii.

U.S.A. MONTANA: Gallatin County, Gallatin Range, Windy Pass Trail, under Picea engelmannii, 4 Aug 2012, EB0114 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Picea engelmannii, 1 Sept 2014, EB0070-14 (MONT).

This species is very close to and likely conspecific with L. zonarioides Kühner & Romagn. (Figure 2B), which occurs in similar habitats and was described from Europe (Hesler and Smith 1979).

Figure 13. 

Lactarius olympianus. Collection EB0070-14 under Picea engelmannii, Tobacco Root Mountains, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 70–140 mm in diameter, broadly depressed–convex to broadly infundibuliform, viscid to dry, smooth to matted–tomentose especially near the margin, zonate to faintly zonate, yellow–buff to buff to pale orange–brown, lighter toward the margin; margin incurved and matted–tomentose to cottony–tomentose when young, remaining so or becoming straight and ± glabrous in age. Lamellae subdecurrent to decurrent, many of them branching, crowded, white to pale cream when young, becoming orange–buff to brown to gray–brown in age. Stipe 20–90 × 15–20 mm, tapering toward the base, smooth, white to pale buff, discoloring brown, often with scattered small scrobicules, hollow. Context firm. Latex copious, white, unchanging. Odor pleasant, fruity, of orange–citrus. Taste acrid.

Basidiospores 6–8 × 5–6.5 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a broken to partial reticulum. Pleuromacrocystidia 60–100 × 7–12 µm, numerous, strongly projecting, fusiform; apex acute. Cheilomacrocystidia 40–61 × 7–10 µm, numerous, strongly projecting, fusiform; apex acute.

Originally described from Michigan under aspen. There are very few subsequent reports. In the GYE, it is here reported with Populus tremuloides from the Teton Range of Idaho, summer.

U.S.A. IDAHO: Teton County, Teton, under Populus tremuloides, 27 July 1991, CLC233 (MONT), 24 Aug 1991, CLC296 (MONT), 26 July 1992, CLC512 (MONT).

This represents the first report of this species from the GYE under the name L. pseudodelicatus. It was previously reported from the GYE as L. cf. zonarius Fr. in Cripps and Miller (1993) and Cripps (2001). The European L. zonarius has slightly larger basidiospores (6.3–9.2 × 5.1–7.4 µm), shorter pleuromacrocystidia (40–50 × 4–6 µm), and an ecology with Quercus (Heilmann-Clausen et al. 1998).

Molecularly, L. pseudodelicatus is very close to a specimen identified as L. aff. wenquanensis Y. Wang & Z.X. Xie, from a humid montane rainforest with Quercus, Castanopsis, and Lithocarpus echinops Hjelmq. in Thailand (Figure 2B) (Le et al. 2007). Lactarius aff. wenquanensis appears to be less robust with shorter pleuromacrocystidia (54–76 × 9.5–12 µm); it also appears to have a different ecology. Lactarius wenquanensis Y. Wang & Z.X. Xie, originally described from China has larger basidiospores (7.5–9.5 × (6–)6.5–7.5 µm) and the type was collected under Picea and Abies, as opposed to aspen (Wang 2007). Lactarius torminosus (Schaeff.) Gray is closely related to L. pseudodelicatus (Fig. 2B), however, L. torminosus typically has smaller basidiomes, a more pink to brick pileus, slightly larger basidiospores (7.5–9.6 × 5.6–6.9 µm), and associates with Betula (Heilmann-Clausen et al. 1998). Lactarius pubescens Fr. is also closely related to L. pseudodelicatus (Figure 2B), and both associate with aspen in similar habitats. Lactarius pubescens is typically less robust and features a more pale pileus, a non-scrobiculate stipe, and smaller pleuromacrocystidia (30–60 × 6.5–10 µm) (Heilmann-Clausen et al. 1998). Lactarius delicatus Burl., described from a deciduous forest in Eastern North America produces white latex that turns yellow (Hesler and Smith 1979).

Figure 14. 

Lactarius pseudodelicatus. Collection CLC512 under Populus tremuloides, Teton Range, Idaho, USA. Scale bar: 2 cm. Photo by C. Cripps.

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.

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.

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).

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 L. 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 L. pubescens in North America is warranted. The Betula associate L. 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 L. pseudodelicatus for distinguishing features for that taxon.

Figure 15. 

Lactarius pubescens. Collection EB303-15 under Betula sp., Boise, Idaho, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 50–80 mm in diameter, depressed–convex to broadly infundibuliform, viscid to dry, smooth to ± matted–tomentose toward the margin, zonate to faintly zonate, yellow–brown to orange–brown, ± lighter toward the margin; margin incurved and matted–tomentose to cottony–tomentose when young, becoming straight and glabrous in age. Lamellae subdecurrent to decurrent, crowded, cream, staining brownish where damaged. Stipe 20–40 × 15–25 mm, equal to tapering toward the base, smooth, dry, cream, ± with small pale brown scrobicules. Context very firm, cream. Latex white, unchanging, staining lamellae brownish. Odor sweet, fruity. Taste slowly acrid.

Basidiospores 7–9 × 5.5–7.5 µm, Q = 1.2–1.4, broadly ellipsoid to ellipsoid; ornamentation forming a highly broken reticulum. Pleuromacrocystidia 40–66 × 4.5–7.4 µm, scarce to scattered, narrowly subfusiform to fusiform; apex acute to moniliform. Cheilomacrocystidia 25–49 × 4.5–5.5 µm, numerous, narrowly subfusiform to fusiform; apex acute to moniliform.

Originally described and reported from rich wet humus along small streams in hardwood forests in Michigan. There are very few subsequent reports. In the GYE, it occurs in rich, moist riparian areas with Populus trichocarpa, summer to fall.

U.S.A. MONTANA: Gallatin County, Bozeman, along Sourdough Creek, under Populus trichocarpa, 2013, CLC2933 (MONT).

Molecularly, this taxon is very close to the European L. evosmus Kühner & Romagn. (Figure 2B), which also associates with Populus, as well as Quercus, and occasionally Salix (Heilmann-Clausen et al. 1998). It is also close to but distinct from the European L. zonarius (Figure 2B). Neither L. evosmus or L. zonarius feature a bearded pileus margin at any point in sporocarp development. Lactarius zonarius v. riparius will likely need to be given species level status and a new name, although this hinges on examination of type material.

Similar taxa in western North America include L. sanmiguelensis Hesler & A.H. Sm., described from under cottonwood in southwestern Colorado that has a pileus with cinnamon–buff zones on a pinkish buff ground color, the role of felt along the margin is pinkish buff, it does not have a distinctive odor, it is instantly and very strongly acrid, the lamellae are strongly anastomosed, pinkish buff, and do not discolor where injured, and the stipe is longer and pale pinkish buff (Hesler and Smith 1979). Bessette et al. (2009) synonymize L. sanmiguelensis and L. subvillosus Hesler & A.H. Sm., the latter being undoubtedly different from the species described here. Lactarius pseudodelicatus is somewhat similar but it has a longer stipe, smaller basidiospores (6–8 × 5–6.5 µm), and much larger pleuromacrocystidia (60–100 × 7–12 µm). Lactarius psammicola A.H. Sm. and L. yazooensis Hesler & A.H. Sm. are similar species with a more Eastern North American distribution in Quercus forests (Hesler and Smith 1979).

Figure 16. 

Lactarius zonarius v. riparius. Collection CLC2933 under Populus trichocarpa, Bozeman, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 60–170 mm in diameter, depressed–convex to infundibuliform, glutinous when wet, with matted fibrils beneath the gluten especially near the margin, ± faintly zonate, pale creamy yellow to pale yellow–brown to golden yellow–brown, discoloring orange–brown to brown where damaged; margin ± faintly tomentose, incurved when young, becoming straight to wavy. Lamellae subdecurrent to decurrent, some forked toward the stipe, crowded, pale cream to pale buff, ± slowly discoloring yellow and eventually orange–brown where damaged. Stipe 20–60 × 30–50 mm, equal to clavate to tapering toward the base, smooth, dry, conspicuously scrobiculate, white, discoloring orange–brown where damaged or in age, solid, becoming hollow. Context firm, white, ± slowly discoloring yellow to orange–brown where damaged. Latex scarce to undetectable, white, ± becoming very pale yellow, and slowly staining damaged tissue yellow. Odor mild to sweet. Taste quickly very acrid.

Basidiospores 7.5–10 × 6–8.5 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a partial reticulum. Pleuromacrocystidia 60–90 × 3–8 µm, rare, mostly near the pileus and between the lamellae, cylindric to fusiform; apex acute to moniliform. Cheilomacrocystidia absent.

In western North America and Mexico under conifers. Also reported from California with Quercus. In the GYE, L. alnicola occurs in wet areas, often along streams in the spruce-fir zone, possibly always in the presence of Picea engelmannii, summer and early fall.

U.S.A. MONTANA: Gallatin County, Gallatin Range, Langhor Road, under Picea engelmannii, 27 Aug, EB0064-14 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Picea engelmannii, 1 Sept 2014, EB0067-14 (MONT).

Lactarius alnicola is phylogenetically very closely related to the European L. scrobiculatus (Scop.) Fr., and may be conspecific, however more specimens need to be sequenced before making this determination final (Figure 2B). For morphological differences, L. scrobiculatus features a heavily bearded pileus margin, and produces white latex which rapidly turns yellow (Kytövuori 1984). Lactarius alnicola, and other members of subsection Scrobiculati Hesler & A.H. Sm. sensu Kytövuori (1984) form a strongly supported clade in the phylogeny (Figure 2B).

Two varieties of L. alnicola have been described: L. alnicola v. pitkinensis Hesler & A.H. Sm., described from Colorado under aspen and conifers, has cream colored to white basidiomes, an acrid taste, unchanging latex, and unchanging (non-yellowing) flesh; L. alnicola v. pungens Hesler & A.H. Sm., described from Michigan in mixed forest, has a dull ochraceous to ochraceous–tan, subviscid, glabrous pileus, an acrid taste, and white, unchanging latex, which stains white paper yellow (Hesler and Smith 1979). Neither appear to fit the taxon described here.

Figure 17. 

Lactarius alnicola. Top and bottom collection EB0064-14 under Picea engelmannii, Gallatin Range, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus to 80 mm in diameter, broadly convex with a depressed center, glutinous when wet, with matted fibrils beneath the gluten especially near the margin, azonate, pale yellow–cream to yellow–tan, discoloring brown in places; margin densely bearded, incurved at least when young. Lamellae subdecurrent, crowded, cream to pale yellow–cream, ± discoloring yellow and eventually rusty brown where damaged. Stipe 30 × 20 mm, tapering toward the base, smooth, dry, white to pale yellow–tan, with small, faint, dull yellow–tan scrobicules, hollow. Context white, ± slowly discoloring pale yellow to faintly tan where damaged. Latex scarce, white, becoming very pale yellow, and slowly staining damaged tissue pale yellow. Odor sweet. Taste acrid.

Basidiospores 7–10 × 5.5–7.5 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a broken to nearly complete reticulum. Pleuromacrocystidia 50–100 × 7–12 µm, abundant, strongly projecting, fusiform to lanceolate; apex acute to moniliform. Cheilomacrocystidia absent.

In montane, rich, moist habitats with Picea engelmannii, late summer.

U.S.A. MONTANA: Park County, Silver Gate, under Picea engelmannii, 13 Aug 2014, EB0052-14 (MONT).

This species, along with L. alnicola, and L. aff. olivinus Kytöv. described below, fall in subsection Scrobiculati as recognized by Kytövuori (1984). Morphologically, it is quite close to the European L. tuomikoskii Kytöv. It is also very close to some interpretations of L. scrobiculatus v. canadensis A.H. Sm., and L. gossypinus Hesler & A.H. Sm., except it has larger basidiospores and pleuromacrocystidia. Lactarius payettensis A.H. Sm. is also similar, but differs by having a more robust, heavily scrobiculate stipe and apparently unchanging latex (Hesler and Smith 1979). Both L. gossypinus and L. payettensis have been previously reported from the GYE (McKnight 1982), however neither were examined for this treatment. Overall, the complex of species surrounding L. scrobiculatus in North America, which includes L. alnicola, L. gossypinus, L. payettensis, L. scrobiculatus v. canadensis, L. scrobiculatus v. montanus Methven, and the two taxa described here (L. aff. tuomikoskii, and L. aff. olivinus) appears to be in need of revision, especially in relation to European taxa such as L. auriolla Kytöv., L. leonis Kytöv., L. olivinus, L. scrobiculatus, and L. tuomikoskii (Kytövuori 1984).

Figure 18. 

Lactarius aff. tuomikoskii. Top and bottom collection EB0052-14 under Picea engelmannii, Silver Gate, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 30–110 mm in diameter, depressed–convex to infundibuliform, viscid when wet, with appressed, agglutinated scales of confluent hairs, especially near the margin, more or less azonate, cream to olive–buff to yellow–tan to orange–tan, ± darker toward the center; margin incurved and wooly–tomentose when young, often forming a cottony rim, becoming straight and more or less glabrous. Lamellae subdecurrent, crowded, cream, staining yellow where damaged and then fading or eventually becoming pale ochraceous. Stipe 30–45 × 10–25 mm, equal to clavate to tapering toward the base, smooth, dry, cream to pale yellow–tan to orange–tan, ± with pale yellow–tan scrobicules, often with a white ring near the apex, solid, becoming hollow. Context white, staining pale yellow at first and then fading. Latex scarce to undetectable, white, becoming yellow, staining tissue yellow and then fading. Odor faintly sweet to faintly spermatic. Taste mild.

Basidiospores 7.5–10 × 5.5–7 µm, Q = 1.3–1.5, ellipsoid; ornamentation forming a partial reticulum. Pleuromacrocystidia 51–100 × 9–14 µm, abundant, strongly projecting, fusiform to lanceolate; apex acute to moniliform. Cheilomacrocystidia absent.

In montane, rich, moist habitats with Picea engelmannii, mid to late summer.

U.S.A. MONTANA: Park County, Silver Gate, under Picea engelmannii, 13 Aug 2014, EB0050-14 (MONT), EB0051-14 (MONT).

This species is morphologically close to the European L. olivinus except for the mild rather than acrid taste. Molecularly (Figure 2B), and ecologically, it is also close, however we refrain from calling it that species until more collections are examined and compared with European material. It is also very close to some interpretations of the North American taxa L. scrobiculatus v. canadensis, and L. gossypinus, except it has larger basidiospores and pleuromacrocystidia. Lactarius payettensis is also similar, but it has unchanging latex, and a strongly acrid taste. See comments under L. aff. tuomikoskii for additional information.

Figure 19. 

Lactarius aff. olivinus. Top collection EB0051-14 and bottom collection EB0050-14 under Picea engelmannii, Silver Gate, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

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.

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.

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).

This is the first report of L. barrowsii from the GYE. Lactarius barrowsii, and other members of section Deliciosi (Fr.:Fr.) Redeuilh, Verbeken & Walleyn, such as L. deliciosus (L.) Gray, L. deterrimus Gröger, and L. 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 L. rubrilacteus. However, in L. 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, L. barrowsii is very close to the hypogeous, spring fruiting, pine associated L. rubriviridis Desjardin, H.M. Saylor & Thiers, which occurs in similar dry habitats in western North America (Nuytinck et al. 2007).

Figure 20. 

Lactarius barrowsii. Top collection EB008-15 (left and right) and bottom collection EB015-15 under Pinus flexilis, Story Hill, Bozeman, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 45–90 mm in diameter, shallowly depressed–convex to broadly infundibuliform, smooth, viscid, zonate, light brown to orange–cream to yellow–orange to orange–brown to carrot to dingy orange, often with green stains; margin incurved when young becoming straight. Lamellae adnate to subdecurrent, crowded to subdistant, cream to pinkish cinnamon to dull pink, discoloring wine red and eventually green where damaged. Stipe 20–40 × 10–25 mm, equal to tapering toward the base, dry, smooth, at first with a light glaucous coating, ± scrobiculate, cream to dull pink to orange–cream, discoloring wine red and eventually green where damaged, solid, becoming hollow. Context white, immediately staining deep wine–red to burgundy. Latex scarce, wine red, staining tissue wine–red to burgundy and eventually green. Odor mild. Taste mild.

Basidiospores 7.5–9.5 × 5–7.5 µm, Q = 1.3–1.5, ellipsoid; ornamentation forming a partial reticulum. Pleuromacrocystidia 40–80 × 4–6 µm, sparse, fusoid; apex acute. Cheilomacrocystidia 30–65 × 6–9 µm, scattered, fusoid; apex acute.

In western North America with Pseudotsuga menziesii and Pinus. In the GYE this species occurs in foothills to low montane areas, near Pseudotsuga menziesii, spring and early summer.

U.S.A. MONTANA: Gallatin County, Bridger Range, Fairy Lake Road, under Pseudotsuga menziesii, 25 June 2013, EB13-040 (MONT); Park County, Absaroka Mountains, George Lake Trailhead, under Pseudotsuga menziesii, 27 June 2014, EB900-14 (MONT).

The European L. sanguifluus (Paulet) Fr. is morphologically similar, however, its lamellae are typically more violet tinged and its stipe is often scrobiculate. Western North American members of the “L. deliciosus” group can appear similar, however, their latex does not start out red as in L. rubrilacteus. The western North American Lactarius barrowsii also has reddish latex, however, it features a whitish to straw colored pileus and ochraceous to pinkish orange lamellae.

Figure 21. 

Lactarius rubrilacteus. Collection EB13-040 under Pseudotsuga menziesii, Bridger Range, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 30–100 mm in diameter, convex to broadly infundibuliform, smooth to faintly areolate, viscid to dry, ± faintly zonate, pale cream to pale yellow to carrot orange, often with green stains especially in age; margin striate when wet, incurved when young and becoming straight. Lamellae adnate to subdecurrent, crowded to subdistant, creamy orange to carrot orange, discoloring orange to reddish and eventally green where damaged. Stipe 30–70 × 5–25 mm, equal to clavate to tapering toward the base, viscid to dry, smooth, creamy orange to carrot orange with a white band toward the apex; discoloring carrot orange to dull reddish and eventually green where damaged, hollow. Context yellowish, immediately staining carrot orange to dull reddish and eventally green. Latex scarce, carrot orange, staining tissue carrot orange to dull reddish and eventually green. Odor mild. Taste mild.

Basidiospores 7.5–10.5 × 5.5–7.5 µm, Q = 1.3–1.5, ellipsoid; ornamentation forming a partial reticulum. Pleuromacrocystidia 40–55 × 3–6 µm, very sparse, subfusiform; apex moniliform. Cheilomacrocystidia 45–60 × 4–9 µm, scarce to numerous, subfusiform; apex moniliform.

In North America with conifers. In the GYE, members of this group occur in montane mixed lodgepole/spruce-fir forests, the spruce-fir zone, and the krummholz zone, summer to fall; there are also reports specifically with Pinus flexilis (Cripps and Antibus 2011) and Pinus albicaulis (Mohatt et al. 2008, Cripps and Antibus 2011), and one collection is reported here with Arctostaphylos uva-ursi, well-separated from any conifers.

U.S.A. MONTANA: Carbon County, Hellroaring Plateau, Hellroaring Creek, among Arctostaphylos uva-ursi, 9 Aug 2015, EB107-15 (MONT); Gallatin County, Gallatin Range, East Fork Hyalite Creek, under Picea engelmannii, 24 Aug 2014, EB0063-14 (MONT); Madison County, Madison Range, Taylor Creek, under Abies lasiocarpa, Picea engelmannii and Pinus contorta, 25 July 2015, EB089-15 (MONT).

While section Deliciosi (Fr.:Fr.) Redeuilh, Verbeken & Walleyn has been resolved as monophyletic (Nuytinck et al. 2007) (Figure 2B), the complex of species surrounding L. deliciosus (L.) Gray in North America is poorly resolved. Using molecular techniques, Nuytinck et al. (2007) showed that L. deliciosus and L. deterrimus Gröger likely do not occur in North America. The collections of the North American varieties of L. deliciosus described by Hesler and Smith (1979) that they analyzed formed a clade separate from the European L. deliciosus and L. deterrimus, but were poorly resolved, with the exception of L. deliciosus v. areolatus A.H. Smith, which formed a monophyletic group. For descriptions of North American members of this group see Hesler and Smith (1979) and Methven (1997).

Lactarius deliciosus and all of its North American varieties, as well as L. deterrimus have been previously reported from the GYE (McKnight 1982, Mohatt et al. 2008, Cripps 2011, Cripps and Antibus 2011). Specimens from the GYE included in the phylogenetic analysis in the present study fall in the poorly resolved North American “L. deliciosus” group including “L. deliciosus v. deterrimus” (Gröger) Hesler & A.H. Sm. and L. deliciosus v. olivaceosordidus Hesler & A.H. Sm. (Figure 2B). Previous reports of L. thyinos from the GYE (McKnight 1982), a northeastern North American member of sect. Deliciosi that occurs in Thuja bogs may refer to the “L. deliciosus” group described here. Overall, this group is in need of revision.

Figure 22. 

“Lactarius deliciosus” group. Top collection EB107-15 among Arctostaphylos uva-ursi, Hellroaring Plateau, Montana, USA. Bottom collection EB089-15 under Picea engelmannii, Pinus contorta, and Abies lasiocarpa, Madison Range, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

Pileus 15–70 mm in diameter, broadly convex to depressed–convex to broadly infundibuliform, ± umbonate, subviscid to dry, smooth to wrinkled–veined, typically darker when young, liver colored to deep scarlet red to red–brown to orange–brown to dingy orange, conspicuously lighter (to yellow–orange) toward the margin in age; margin ± striate when wet, slightly incurved to straight when young, remaining straight or becoming slightly wavy in age. Lamellae subdecurrent, crowded to subdistant, cream to creamy yellow to pale tan to pale orange–tan. Stipe 20–70 × 8–13 mm, equal to slightly clavate, smooth, dry, faintly white–pruinose when young, dingy orange to red–orange, solid, becoming hollow. Context pale tan to red–orange. Latex scarce to abundant, white, unchanging. Odor mild. Taste mild to slightly bitter.

Basidiospores 7–9.5 × 6–8 µm, Q = 1.1–1.4, subglobose to ellipsoid; ornamentation forming a broken to nearly complete reticulum. Pleuromacrocystidia 40–90 × 5–10 µm, scattered to numerous, subfusiform; apex obtuse to broadly acute. Cheilomacrocystidia 20–50 × 5–9 µm, scattered to numerous, subfusiform; apex obtuse to broadly acute.

In Eurasia and North America with Picea. In the GYE, this species occurs in moist areas and along streams (although it can also occur on drier upland sites) in the montane spruce-fir zone, possibly always in the presence of Picea engelmannii, summer to fall.

U.S.A. MONTANA: Gallatin County, Gallatin Range, East Fork Hyalite Creek, under Abies lasiocarpa and Picea engelmannii, 25 Sept 2013, EB200-13 (MONT); under Abies lasiocarpa, Picea engelmannii and Pinus contorta, 24 Aug 2014, EB0062-14 (MONT); Madison County, Tobacco Root Mountains, Branham Lakes, under Picea engelmannii; 1 Sept 2014, EB0069-14 (MONT); Sweet Grass County, Crazy Mountains, Big Timber Creek, under Abies lasiocarpa and Picea engelmannii, 1 Aug 2015, EB094-15 (MONT).

This is the first report of this species from the GYE under the name L. badiosanguineus. In North American treatments (e.g. Hesler and Smith 1979, Bessette et al. 2009), this species may have gone under the name L. hepaticus Plowr. Previous reports of L. subdulcis (Pers.) Gray from the GYE (McKnight 1982) likely refer to L. badiosanguineus. The European L. hepaticus has a duller, browner pileus (although it can be deep red), yellowing latex and flesh, an acrid taste, and it associates with Pinus in nutrient-poor, acidic soils (Kränzlin 2005). The European L. subdulcis has a more orange–brown to brown pileus (although it can be reddish), a mild to unpleasant smell, a bitter–acrid taste, and an association with Fagus (Heilmann-Clausen et al. 1998, Kränzlin 2005). Phylogenetically, L. badiosanguineus appears to be fairly closely related to but distinct from both L. subdulcis and L. hepaticus (Figure 2C).

Lactarius badiosanguineus is closely related to L. subviscidus Hesler & A.H. Sm., L. sphagneti (Fr.) Neuhoff, and L. fulvissimus Romagn. Lactarius subviscidus features typically smaller, more fragile basidiomes with a more uniformly orange pileus, and latex that stains white paper yellow (Hesler and Smith 1979); L. subviscidus appears to be confined to the coastal forests of the Pacific Northwest of North America. According to Heilmann-Clausen et al. (1998), the European L. sphagneti features a more distinctly two-toned pileus with a paler margin and darker center (although L. badiosanguineus also often displays this character at least in the GYE) as well as more densely reticulate spores with a stronger amyloid reaction. The European L. fulvissimus typically features basidiomes which are more orange overall, white latex which often turns yellow, basidiospores with an ornamentation of small pointed warts, and an ecology with deciduous trees such as Fagus, Quercus, Tilia, Populus, and Corylus, more rarely with conifers (Heilmann-Clausen et al. 1998, Kränzlin 2005).

Lactarius badiosanguineus is also very similar to L. atrobadius Hesler & A.H. Sm., reported from the Pacific coastal Picea sitchensis belt in North America. Lactarius atrobadius appears to have darker basidiomes, however, a more in depth molecular and morphological comparison between the two taxa is warranted. Lactarius lanceolatus O.K. Mill. & Laursen is also similar, however it typically produces basidiomes which are overall more orange with larger pleuromacrocystidia (73.5–127 × 6.5–10 µm), and it occurs above tree line with Salix. See comments under L. luculentus v. laetus Hesler & A.H. Sm. for features distinguishing it from L. badiosanguineus.

Figure 23. 

Lactarius badiosanguineus. Top collection EB0069-14 under Picea engelmannii, Tobacco Root Mountains, Montana, USA. Bottom collection EB200-13 under Picea engelmannii and Abies lasiocarpa, Gallatin Range, Montana, USA. Scale bars: 2 cm. Photos by E. Barge.

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.

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.

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).

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 L. badiosanguineus and L. luculentus v. laetus, both of which are less robust and not acrid.

Figure 24. 

Lactarius rufus. Collection EB0076-14 under Pinus contorta and Picea engelmannii, Gallatin Range, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 30–50 mm in diameter, broadly convex to broadly infundibuliform, ± umbonate, smooth, viscid when wet but soon dry, yellow–orange to dull orange to brilliant orange to orange–brown; margin straight when young to wavy in age. Lamellae adnate to decurrent, crowded to subdistant, cream to pale yellow–orange. Stipe 20–60 × 5–10 mm, equal to slightly clavate to tapering toward the base, smooth, subviscid to dry, lighter than to concolorous with the pileus, typically getting lighter toward the apex, sometimes with scattered small scrobicules present, solid, becoming hollow. Context cream to pale yellow. Latex scarce, white, unchanging. Odor mild. Taste mild to slightly bitter.

Basidiospores 7–10 × 5.5–8 µm, Q = 1.2–1.5, broadly ellipsoid to ellipsoid; ornamentation forming a very broken reticulum. Pleuromacrocystidia 60–98 × 8–12 µm, scattered to numerous, strongly projecting, subfusiform to fusiform; apex acute. Cheilomacrocystidia none observed, possibly absent.

In western North America with conifers. In the GYE it occurs in the montane spruce-fir zone, summer.

U.S.A. MONTANA: Sweet Grass County, Crazy Mountains, Big Timber Creek, under Abies lasiocarpa and Picea engelmannii, 1 Aug 2015, EB097-15 (MONT).

This is the first report of this taxon from the GYE under the name L. luculentus v. laetus. Previous reports of L. aurantiacus (Pers.) Gray from subalpine areas in the GYE (McKnight 1982) may refer to L. luculentus v. laetus.

Variety laetus is distinguished from var. luculentus by a brighter orange pileus as opposed to orange–brown and a mild to slightly bitter taste as opposed to slightly acrid (Hesler and Smith 1979). At the molecular level, there is some divergence within L. luculentus (Figure 2C, see also Barge et al. 2016) and there may be more than one species hiding under the name, although more specimens need to be examined and sequenced before making any nomenclatural changes.

Lactarius luculentus v. laetus is very closely related to L. aurantiacus and L. lanceolatus (Figure 2C) and morphological differences between them are subtle. Lactarius lanceolatus appears to have longer and more numerous cheilomacrocystidia (35.5–89 × 5–10 µm), longer pleuromacrocystidia (73.5–127 × 6.5–10 µm), as well as an alpine ecology with Salix. Lactarius aurantiacus also appears to have slightly longer pleuromacrocystidia (68.6–119.4 × 7.6–12.7 µm), and, while it occupies similar habitats to L. luculentus v. laetus, it may be absent from western North America outside of Alaska (Barge 2015).

The closely related Betula associate L. lapponicus Harmaja (syn.: L. duplicatus A.H. Sm.) (Figure 2C) has yellowing latex as opposed to white, unchanging latex, and appears to have a more boreal to arctic distribution (Heilmann-Clausen et al. 1998); it has not been reported from the Rocky Mountains. The closely related L. substriatus A.H. Sm. and L. subflammeus Hesler & A.H. Sm. (Figure 2C) have slightly smaller basidiospores (6.5–9 × 6–8 µm, 7.5–9 × 6.5–7.5 µm respectively), a slightly acrid taste, and are scarlet when young (Hesler and Smith 1979). The latex of L. substriatus also slowly stains pale yellow. Phylogenetic analyses suggest L. substriatus and L. subflammeus are conspecific, and that yellowing latex is a variable feature within the combined species, although more specimens should be sequenced before making this determination final. Neither of these taxa have been reported from the GYE and their distribution seems to be centered along the Pacific Northwest coast. The morphologically similar L. subviscidus, also centered along the Pacific Northwest coast, typically has smaller and more fragile basidiomes, a slightly acrid taste and unchanging latex which stains white paper yellow (Hesler and Smith 1979). In the Rocky Mountains, L. luculentus v. laetus and L. badiosanguineus occur in the same habitat and can easily be confused. However, the latter has slightly smaller basidiospores (7–9.5 × 6–8 µm) and typically has a more red–brown pileus which is often darker toward the center and lighter toward the margin.

Figure 25. 

Lactarius luculentus v. laetus. Collection EB097-15 under Abies lasiocarpa and Picea engelmannii, Crazy Mountains, Montana, USA. Scale bar: 2 cm. Photo by E. Barge.

Pileus 10–45 mm in diameter, convex to depressed–convex at first, becoming plane to infundibuliform, with or without a small papilla, smooth, sometimes faintly scaly toward the center, viscid to dry, azonate, deep orange–brown to deep orange when immature becoming light to deep orange, often blotchy; margin incurved to straight when immature, becoming straight to upturned and often slightly wavy when mature, ± slightly crenulate. Lamellae adnate to subdecurrent, slightly crowded, pale cream to pale yellow to pale orange, discoloring brownish orange in age or where damaged. Stipe 10–20 × 2.5–7.5 mm, equal to clavate, smooth, dry, at first covered by faint whitish pubescence, pale orange, discoloring dingy orange to dingy light brown where damaged, hollow. Context pale orange. Latex scarce to undetectable, watery, white, unchanging. Odor mild. Taste mild.

Basidiospores 8–10 × 6–8 µm, Q = 1.1–1.4, broadly ellipsoid; ornamentation forming a broken reticulum. Pleuromacrocystidia 73.5–127 × 6.5–10 µm, scattered to abundant, strongly projecting, fusiform to lanceolate; apex acute to moniliform. Cheilomacrocystidia 35.5–89 × 5–10 µm, sparse to abundant, strongly projecting, conical to fusiform; apex acute to moniliform.

Widespread in arctic-alpine areas in the northern hemisphere with Salix. In the GYE, it occurs above tree line in alpine areas with Salix reticulata, S. arctica, and S. planifolia, late summer.

U.S.A. MONTANA: Carbon County, Beartooth Plateau, Highline Trail, among dwarf and shrubby Salix spp., 1 Aug 1997, ZT6214 (MONT); among Salix spp. 7 Aug 1998, ZT6412 (MONT); among Salix reticulata, 20 Aug 1999, CLC1389 (MONT); 5 Aug 2008, CLC2358 (MONT); 27 July 1997, CLC1139 (MONT); Carbon County, Hellroaring Plateau, Hellroaring Creek, among Dryas octopetala and shrubby Salix spp., 8 Aug 2015, EB104-15 (MONT); among Dryas octopetala, shrubby Salix spp. and S. reticulata, 8 Aug 2015, EB105-15 (MONT); among Betula glandulosa and shrubby Salix spp., 9 Aug 2015, EB103-15 (MONT). WYOMING: Park County, Beartooth Plateau, Solifluction Terraces, among Salix reticulata, 20 July 2001, CLC1578 (MONT); 13 Aug 2007, CLC2319 (MONT); among Salix arctica, S. planifolia and S. reticulata, 17 Aug 2013, EB 105-13 (MONT).

Lactarius lanceolatus is closely related to L. aurantiacus, and L. luculentus/L. luculentus v. laetus (Figure 2C). It can be distinguished from L. luculentus/L. luculentus v. laetus in having longer cheilomacrocystidia and an alpine ecology with Salix, whereas the latter occur with conifers. Currently, we are unaware of any solid morphological differences between L. lanceolatus and L. aurantiacus. Lactarius lapponicus (syn.: L. duplicatus), which occurs in boreal and arctic-alpine areas in the Northern Hemisphere with Betula, and possibly other hosts, is also closely related, yet it features strongly yellowing latex (Heilmann-Clausen et al. 1998). Other similar orange taxa in western North America such as L. substriatus, L. subflammeus, and L. subviscidus all occur below tree line with conifers, and their distributions seem to be centered along the Pacific Northwest coast (Hesler and Smith 1979). See comments under L. badiosanguineus for features differentiating L. lanceolatus from that species.

Figure 26. 

Lactarius lanceolatus. Top collection EB103-15 under shrubby Salix spp. and Betula glandulosa, Hellroaring Plateau, Montana, USA. Bottom collection EB105-13 among Salix arctica, S. reticulata, and S. planifolia, Beartooth Plateau, Wyoming, USA. Scale bars: 2 cm. Photos by E. Barge.