Austroboletus mutabilis Halling, T.Osmundson & M.A.Neves

  • Family

    Boletaceae (Basidiomycota)

  • Scientific Name

    Austroboletus mutabilis Halling, T.Osmundson & M.A.Neves

  • Primary Citation

    Austroboletus mutabilis sp. nov. from northern Queensland
    Muelleria 24: 32. 2006

  • Type Specimens

    Specimen 1: Isotype -- R. E. Halling 8745

    Specimen 2: Paratype -- R. E. Halling 6835

  • Description

    Protologue: A specibus Austroboletorum ubique coloribus pileorum mutabilibus; ut videtur plaga sporarum levi sed vero erasa distinguenda.

    Type: AUSTRALIA. Queensland, Mareeba, ±12-15 km E of Kuranda-Mareeba Highway along Davies Creek Road, Davies Creek N.P., 17°1’S, 145°35’E; ±720 m, 9 Feb 2006, R. E.Halling 8745 (holotype BRI; isotype NY).

    Macroscopic description: Pileus (2-)3-6 cm broad, convex or pulvinate to plano-convex, glutinous when young and fresh, soon viscid to subviscid or dry, matted to glabrous beneath the gluten, dark red to brownish red (10B-F8 to 8-9C-D8) when young, soon fading to brownish orange (7B7-5B7 to 7D8), becoming orangish yellow (6C-D8), then eventually yellowish (4A7,6), sometimes with adherent glutinous universal veil remnants at margin. Flesh soft, white, unchanging, with mild odor and slightly acidic taste. Tubes adnate to adnexed, white at first, soon becoming pale porphyry pinkish brown (7-8C-D5-4), staining brownish yellow when bruised, with pores pale pink (7A2) to greyish pink (7B2), staining darker pink or light brown. Stipe (4-)6-12 cm long, 5-10(-12) mm broad, equal to slightly broader below, then tapered slightly toward base, dry, white and alveolate-reticulate to lacerate nearly overall, sometimes coarsely so, with ridges slightly finer above and near apex, typically draped (except for apex) with translucent yellow to dull or dark ochraceous to dark honey brown glutinous universal veil remnants, with white, solid interior eventually becoming pithy to slightly hollow, with white basal mycelium. NH4OH: on pileus, immediately grass green on lighter portions; dark green on redder portions, becoming orange at point of application with green halo; negative on flesh; faint pink on glutinous veil that adheres to stipe; negative on stipe surface.

    Microscopic description: Basidiospores greyish red (9C-D3) to reddish brown (8-9E7) in deposit, 11.9-14.7 × 4.9-7 µm, Q = 2.23, n = 20, x = 12.9 × 5.8 µm, broadly subfusoid to elongate amygdaliform, with wall minutely pitted, eventually more obviously pitted and dissected by short, meandering fissures that occasionally isolate irregular ridges, with a smooth to conspicuously eroded suprahilar plage, cyanophilic, brownish yellow in KOH, inamyloid or sometimes dextrinoid in mass in Melzer’s. Basidia 25-35 × 10-13 µm, 4-sterigmate, clavate, hyaline or sometimes with granular content. Hymenial cystidia present as scattered, fusoid to lageniform pleurocystidia and abundant, cylindric to elongate-clavate cheilocystidia, without differentiated contents. Tube trama boletoid, diverging from a central zone of brownish yellow hyphae, with lateral elements 5-8 µm broad, becoming gelatinized with age. Pileipellis a suberect to erect, tangled trichodermium embedded in a gelatinous matrix; hyphae with a pale brownish pigment dissolving in KOH, non-encrusting and amorphous in Melzer's, with terminal elements hyaline, smooth and thin-walled, cylindrical to elongate, 3.5-7 µm wide. Pileus trama interwoven, hyaline, inamyloid, with elements 5-14 µm wide, smooth, thin-walled. Stipitipellis hymeniform, with sphaeropedunculate or short-clavate to elongate clavate caulocystidia, rarely fusoid to sublageniform and projecting. Stipe trama hyphae parallel, cylindric, hyaline, inamyloid. Clamp connections absent.

    Habit, habitat, and distribution: Gregarious to scattered, sometimes solitary, rarely espitose on coarse, granitic soil in sclerophyll woodlands with Acacia aulacocarpa Cunn. ex Benth., Allocasuarina littoralis (Salisb.) L. A. S. Johnson, A. torulosa (Aiton.) L. A. S. Johnson, Eucalyptus intermedia R. Br., and Xanthostemon sp. Known from the Paluma Range (Mt. Spec section) north of Townsville and the Atherton Tableland west of Cairns.

    Commentary: The major distinguishing macroscopic feature of this austrobolete is the dramatic colour shift on the pileus that occurs as the basidiomata age. While this colour shift may occur as a consequence of time, the shift also appears to be mediated by exposure to light and/or fluctuation in humidity. Without exception, the immature or button stages are dark red and pass through an orange stage and eventually become yellow as the basidiomata mature. Intermediate forms can be found that exhibit combinations of these colours and these appear to result from differential exposure to light and air (i.e., one pileus overlaying a portion of another). Because solitary basidiomata are found that may exhibit only one of the colour phases, collectors and naturalists should be aware of this temporal colour change. Also, the pileus is glutinous at first, but becomes viscid to subviscid and then dries out during maturation and with exposure. The gluten extends from the pileus downward and overlays the stipe when young, then dries and shrinks as the basidiomata expand with maturation. The gluten then is distributed in patches or annular zones. With the light microscope, the suprahilar plage appears smooth on spores that are otherwise conspicuously ornamented with pits and fissures. Ultrastructural detail seen with the scanning electron microscope reveals a smooth suprahilar plage on young spores, which then appears eroded at maturity.

    Commentary: Corner’s (1972) aquarelle of Austroboletus mucosus (Corner) Wolfe illustrates a similar yellowish pileus colour and deposition of glutinous veil remains as on the stipe of A. mutabilis, but A. mucosus is tawny brown at first (not red) with a white to cream coloured stipe (not entirely white), and produces spores with isolated verrucae (not with meandering ridges and fissures) restricted to the broad, central portion. Sympatric taxa in Davies Creek National Park include Austroboletus cfr. austrovirens Fechner et al., and something near A. occidentalis Watling & N.M. Greg. The former has a green pileus and stipe ornamentation and the latter is uniformly coloured a cinnamon brown to a light cocoa brown throughout development with a much more complex pattern of reticulation (but not lacerated) on the stipe surface. Other species listed as occurring in Australia (May & Wood 1997), i.e., A. eburneus, A. niveus, A. novaezelandiae, A. lacunosus, and A. subflavidus do not have red pilei.

  • Sorry, no descriptions available for this record.