Phylloporia microspora (Ryvarden) Decock & Amalfi, 2025

Phylloporia microspora (Ryvarden) Decock & Amalfi , comb. nov. MycoBank MB 851909. Figs 7 View Fig , 8 View Fig .

Basionym: Inonotus microsporus Ryvarden, Kew Bull. View in CoL 54 (3): 803. 1999. MB 459949.

Typus: Zimbabwe, Matebeleland North Province, Victoria Falls , Miombo forest behind the statue of D. Livingstone, ~ S17°55’22”, E25°50’49”, on dead trunk, Colophospermum mopane View in CoL ( Fabaceae View in CoL ), 23 Jan. 1989, L. Ryvarden, Ryvarden 26485 (holotype O; GoogleMaps isotype K). GoogleMaps

Description: Basidiomata annual, pileate, sessile, gregarious, emerging simultaneously in clusters, with “a hundreds of pilei covering 1.5 m of standing trunk” (fide Ryvarden 1999) (in the type, the cluster of basidiomes is 70 mm high, 75 mm wide); individual pilei mostly superposed, emerging from a common base, closely imbricated, with adjacent pilei in rows frequently laterally fused to form wavy , compound pilei, individually slightly spathulate to broadly attached, projecting horizontally, slightly downward (10–)15–25(–30) mm, 15–30 mm wide, from 0.5 mm thick at the very margin up to 6 mm the thickest part near the base, mostly applanate in section; pileus surface smooth, or radially very faintly wrinkled on drying, brownish orange [5C(3–4)] near the margin progressively nearly mostly uniformly light brown when dry [5D(6–7), golden brown],slightly darker at the base [6D(5–6), light brown, cinnamon brown]; margin thin to thick, rounded, entire, mostly regular in outline, rarely slightly wavy, likely white when fresh, drying whitish, pale yellowish grey, cork-coloured [4A(2–3) to 5C3], extending below 0.5–1.5 mm wide; pore surface plane, the pore field starting at about 0.5–1.5 mm behind the very margin, leaving a pale greyish yellow sterile zone, the pore field mostly greyish to pale greyish orange, pale greyish orange to yellowish brown (5[B–C]3 to 5D5, honey yellow, oak brown, mustard brown), slightly glancing; pores mostly round to angular, overall 5–6(– 7) / mm when dry, (110–)120–170(–180) µm wide (av. = 146 µm wide), occasionally radially ellipsoid to oblong, 190–220 × 140–160 µm, or lobed up to 250 × 200 µm; dissepiments thin to moderately thick, (25–)32–60(–65) µm thick (av. = 45 µm), not agglutinated, with free hyphal tips, appearing slightly lanose under the lens; context homogeneous, without black line, shiny, 1–6.0 mm thick at the base [5(C–D)6], brownish orange to light brown; tube layer up to 1.2 mm deep, concolourous or slightly darker than the context, light brown [6D(5–6)]; context and tube layer discolouring to reddish brown in 3 % KOH, then pale brown. Hyphal system monomitic, both in the context and hymenophoral trama; generative hyphae simple septate, thinto slightly thick-walled, hyaline, yellowish to light golden brown, darker in KOH, scarcely ramified, except at the very basal segment, the branches constricted at their emergence point, soon growing parallel to the mother hyphae; in the context, hyphae with a parallel to subparallel (synclinal) orientation, mostly moderately thick-walled with the lumen widely open, septate, but with long aseptate segments, 2.0–2.5 µm at the very basal segment, (3.0–)3.3–5.2(–5.4) µm diam. (av. = 4.4 µm); pileus surface with prostrate hyphae, mostly unbranched, identical to the contextual hyphae; in the hymenophoral trama hyphae with a subparallel disposition, thin- to slightly thick-walled, the lumen widely open, septate, but with long aseptate segments or with occasional with secondary septa, little branched, except at the very basal segment, 2.0–2.3 µm at the very base (2.3–)2.6–4.7(–5.0) µm diam. (av. = 3.2 µm). Hymenium: Basidioles slightly pyriform to broadly clavate, 6.0–9.0 × 3.5–4.5 µm; mature basidia broadly clavate, with four sterigmata, 9–11 × 4–5 µm; cystidioles few, fusoid, thin-walled; basidiospores ellipsoid to slightly ovoid, or shortly oblong, appearing somewhat angular on drying, thick-walled, smooth, hyaline to pale yellowish in KOH, without reaction in Melzer’s reagent, (3.0–)3.2–3.8 × 2.0–2.5 μm (av. = 3.5 × 2.2 µm), R = 1.3–1.4–1.8(–1.9) (ave Q = 1.5).

Phylogenetic affinities: The species, hitherto, has no close relative within the current Phylloporia lineage ( Fig. 1 View Fig ).

Ecology (substrate, host, habitat): On dying, standing trunk, Colophospermum mopane (locally known as Mopane) ( Fabaceae ), in seasonally dry, open woodlands.

Geographic distribution: Currently known from a single locality, the Victoria Falls, in Southwestern Zimbabwe.

Notes: Phylloporia microspora is characterised by seasonal, multiple, gregarious, basidiomes, arising simultaneous from a common base, small- to medium-sized (up to 15–25(–30) mm long × 15–30 mm wide), slightly spathulate to broadly attached with smooth, mostly uniformly light brown pilei ( Fig. 7 View Fig ), and 5–6 pores / mm. The hyphal system is homogeneously monomitic. The basidiospores are narrowly ellipsoid to shortly oblong, 3.2–3.8 × 2.0–2.5 μm ( Fig. 8 View Fig ). Its sole known habitat for the time being is the low altitude, low rainfall, seasonally dry Zambezian open forest and perhaps, more specifically, the Mopane Forest that should be the local native vegetation in the neighbourhood of Victoria Falls, in Zimbabwe ( White 1983, Mapaure 1994).

Phylloporia microspora has no close morphological relative in its known habitat of occurrence nor, hitherto, in tropical Africa or out of Africa. In a phylogenetic perspective, it stands on an isolated branch ( Fig. 1 View Fig ).

To some extent, but superficially, P. microspora reminds of P. flabelliformis and P. gabonensis ( Decock et al. 2015, Ryvarden 2019). These three species share the reproduction strategy with multiple, simultaneous, gregarious emergence of short-living (seasonal) basidiomes, light-coloured pileus, the monomitic hyphal system, and the growth from trunks of small-stemmed trees ( Decock et al. 2015). These similitudes are only superficially comparable, however. The basidiomes of P. microspora emerge from a common base whereas, inversely, in both P. flabelliformis and P. gabonensis , the basidiomes emerge individually from the trunk. Phylloporia microspora also differs from both above-mentioned species in having denser, hard corky basidiomes, which are much softer, fragile when dry in the two other species. In an ecological context, P. microspora was found growing from Colophospermum mopane ( Fabaceae ), a markedly xeric species found in the low altitude, low rainfall areas, seasonally dry Zambezian open forest, in Zimbabwe ( White 1983, Mapaure 1994). Phylloporia gabonensis and P. flabelliformis were found growing on two Euphorbiaceae ( Dichostemma glaucescens and Anthostema aubryanum ) in the Western edge of Central Africa, in Gabon, or in biogeographical term, the Lower Guinean rainforest ( White 1983), which is a humid to very humid, moisture-buffered, closed forest.