Lactarius repraesentaneus Britzelm.

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 : 13-16

Taxon classification Fungi Russulales Russulaceae

4. Lactarius repraesentaneus Britzelm. Figure 6

Lactarius repraesentaneus The following morphological description includes data from Colorado specimens listed in Barge et al. (2016).

Description.

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.

Ecology and distribution.

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.

Specimens examined.

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).

Discussion.

Due to its conspicuously bearded margin, and violet staining tissue, Lactarius 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 Lactarius 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 Lactarius uvidus (Fr.) Fr., Lactarius aspideus (Fr.) Fr., Lactarius salicis-reticulatae Kühner, Lactarius montanus (Hesler & A.H. Sm.) Montoya & Bandala, Lactarius pallidomarginatus , and Lactarius brunneoviolaceus M.P. Christ., etc. occur together in a weakly supported clade, that corresponds with section Uvidi (Konr.) Bon (Figure 2A).