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Species Information
Summary: Features include 1) resupinate growth on dead wood, slash, or plant debris, 2) a fruitbody that is pellicular, white to cream, smooth, the margin not distinct, rhizomorphs sometimes present, 3) spores that are elliptic to subcylindric and rounded at base, 4) absent cystidia, and 5) a monomitic hyphal system, the hyphae with clamp connections. Hjortstam & Larsson (Windahlia 21, 1994) consider Fibulomyces a synonym of Leptosporomyces according to Ainsworth & Bisby''s Dictionary of the Fungi, Ninth Edition: this would makes the correct name Leptosporomyces mutabilis (Bres.) Krieglst. Z. Mykol. 57(1): 53. 1991. Ginns(5) uses Fibulomyces in 1993, but Ginns(23) uses Leptosporomyces in 1998. On the other hand, the online Species Fungorum, accessed August 29, 2012, uses Fibulomyces mutabilis.
Leptosporomyces mutabilis is found in BC, OR, ID, MB, ON, AZ, CO, IA, IL, IN, MI, MN, MO, PA, WV, (Ginns), Austria, Czechoslovakia, Finland, France, Germany, Italy, Norway, Poland, Sweden, United Kingdom, Turkey, USSR, (Julich, but Eriksson suggests that the material cited is heterogeneous: "According to him to hyphae [sic] should be of about equal width... but in some specimens the basal hyphae are characteristically wider").
Fruiting body: resupinate, thin, pellicular (=athelioid), loosely attached "by a soft, scarcely developed subiculum"; white (in herbarium often yellowish); smooth; margin indeterminate [not distinct], rarely finely fibrillose under 50x lens; thin rhizomorphs present in some specimens, (Eriksson), resupinate, forming thin but more or less dense membranous-tomentose patches several centimeters to decimeters across, loosely attached to substrate, cottony, soft, subiculum poorly developed; white becoming cream; smooth; margin "diffuse, sometimes with ill-defined rhizomorphs", (Breitenbach), spore deposit white (Buczacki)
Microscopic: SPORES (3)4-5 x (1.5)2-2.5 microns, elliptic to subcylindric, rounded at base, "in side view both sides may be somewhat convex or the adaxial side or both sides are straight", (if the sides mainly straight, they may be parallel or somewhat converging in the apical direction), smooth, inamyloid, thin-walled; BASIDIA 4-spored, 12-15(20) x 4-5 microns, clavate to subcylindric, with basal clamp connection; CYSTIDIA none; HYPHAE monomitic, "most of the hyphae thinwalled but the basal ones somewhat thickened, varying in width, in some forms of about equal width, in one form the basal hyphae are characteristically wide, 5-7(-10) microns, with clamps, anastomoses frequent, crystalline encrustation especially on the subhymenial hyphae", (Eriksson), SPORES 4-5 x 2-2.5 microns, elliptic, smooth, inamyloid, colorless; BASIDIA 2-4-spored, 11-18 x 3.5-4 microns, clavate, with basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic 3-4 microns wide, BASAL HYPHAE rather thick-walled, the rest thin-walled, some hyphae encrusted with crystals, all septa with clamp connections, (Breitenbach)
Habitat / Range
on dead wood of conifers, according to literature on plant debris on ground, (Breitenbach), Abies lasiocarpa (Subalpine Fir), Carya sp. (hickory), Pinus ponderosa (Ponderosa Pine), Pseudotsuga menziesii (Douglas-fir), Quercus gambelii (Gambel''s Oak); slash; associated with a white rot, (Ginns), on small debris on ground, (Eriksson), fall, winter, spring; also rarely on peaty soil, (Buczacki)
Similar Species
Leptosporomyces septentrionalis has somewhat narrower spores and has rhizomorphs, whereas L. mutabilis normally lacks rhizomorphs, (Breitenbach), Leptosporomyces septentrionalis has subcylindric to subfusiform spores that are 5-6.5 microns long, often has a rose tint, and has rhizomorphs, (Eriksson), Leptosporomyces septentrionalis has oval spores (slightly broader at the base), 5-6 x 1.5-2.0 microns, (Ginns(23)); Leptosporomyces fuscostratus has slightly shorter spores, (Ginns(23)); Leptosporomyces galzinii has spores 3.0-4.2 x 1.8-2.2 microns, slightly smaller basidia, and slightly narrower hyphae, (Ginns(23)); Leptosporomyces montanum has larger spores and basidia (Ginns(23)). See also SIMILAR section of Leptosporomyces montanus.
