Acantholichen, Lotsy, 1907

Marcano, Vicente, 2022, Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s. str. (Agaricales, Hygrophoraceae) from northern South America, Phytotaxa 574 (3), pp. 199-225 : 220

Key to Acantholichen , Cyphellostereum and Dictyonema s.str. in Venezuela

1a. Thallus microsquamulose to microfruticulose, pruinose; squamules densely and dichotomously branched from the tips; photobiont forming clusters of short, irregularly coiled threads (chroococcoid) inside the thallus microsquamulose; soredia absent; upper and lower surfaces in microscope view forming apically thickened, distinctly spiny, pyriform to subglobose, variable in size, sometimes elongate hyphae (acanthohyphidia); clamp connections absent............................................. Acantholichen dendroideus

1b. Thallus composed of distinct fibrils including cyanobacterial filaments ( Rhizonema ); acanthohyphidia absent; clamp connections present or absent ................................................................................................................................................................................2

2a. Thallus directly on bark of trunks or branches; lobes semicircular and/or hemispherical, variable in color, size and shape; basidiocarp N–; Venezuelan Andes or Guayana Highlands................................................................................................................................ (3)

2b. Thallus on mosses, liverworts or soil, appressed filamentous or loose and not forming semicircular lobes; basidiocarp N+ or N–; Venezuelan Andes (Sierra Nevada de Mérida) ............................................................................................................................... (4)

3a (2). Thallus on tree branches; lobes projecting parallel from the substrate, semicircular and hemispherical, variable in color, size and shape; surface hirsute; clamp connections present; basidiocarp with resupinate patches dispersed on the underside and resembling large, irregular attachment, hapters, margin fibrillose; Venezuelan Andes (Sierra Nevada de Mérida) ..... Dictyonema subsericeum

3b. Thallus on tree trunk, shelf–like filamentous, forming semicircular lobes, projecting upright from the substrate, surface areolate, rugose; clamp connections absent; basidiocarps forming irregular, reticulate, resupinate patches dispersed on the underside, margin entire; Guayana Highlands (Cerro Duida, Alto Orinoco).................................................................................. Dictyonema duidense

4a (2). Hymenophore resupinate; jigsaw-puzzle-shaped hyphal sheath present or absent; prothallus absent; clamp connections present or absent.............................................................................................................................................................................................. (5)

4b. Hymenophore corticioid; jigsaw-puzzle-shaped hyphal sheath present; prothallus present; clamp connections present .............. (6)

5a (4). Jigsaw-puzzle-shaped hyphal sheath absent; fibrils not penetrated by tubular fungal hyphae haustoria, horizontally arranged and closely appressed; cyanobacterial filaments 8–10 μm wide; clamp connections present; basidiocarp surface finely arachnoid, N– ................................................................................................................................................................ Cyphellostereum mucuyense

5b. Jigsaw-puzzle-shaped hyphal sheath present; fibrils penetrated by tubular fungal hyphae haustoria, ascendent and loosely arranged; cyanobacterial filaments> 10 μm wide; clamp connections present or absent; basidiocarp surface smooth, N+ (pink) ......................................................................................................................................................................................................... (7)

6a (4). Fibrils irregularly arranged, ascending or erect; cyanobacterial filaments not divided, 20–25 μm wide; hymenophores forming stereoid-corticioid patches, upper surface smooth, lower surface pruinose, spongy, N+ (red)......................... Dictyonema andinum

6b. Fibrils horizontal or subascending; cyanobacterial filaments divided, 13–17 μm wide hymenophores raised from the thallus, resembling apothecial discs, surface pale yellowish, smooth, margins white, minutely tomentose; N .......... Dictyonema umbricola

7a (5). Thallus developing a mat of interwoven fungal–cyanobacterial fibrils, leaving interspaces; cyanobacterial filaments 12–15 μm wide; clamp connections present; basidiocarp developed as effuse patches, with pruinose surface, margins slightly involute ......... .................................................................................................................................................................... Dictyonema subinvolutum

7b. Thallus forming a thin crust (1.75–2 mm), bordered by a discontinuous, narrow, white margin projecting vertical from the substrate; cyanobacterial filaments 12–17 μm wide; clamp connections absent; basidiocarp hapteriform, with finely reticulate surface ......... ............................................................................................................................................................................... Dictyonema laurae