Tremella dirinariae Diederich, Millanes & Wedin

Index Fungorum number: IF551494 Facesoffungi number: FoF01008

Etymology: In reference to the host Dirinaria.

Holotype: Harris 37673 (NY).

Lichenicolous on the thallus of Dirinaria aegialita, not gall-inducing, not causing any visible damage to the host. Known only from the type locality in Florida. Sexualmorph: Basidiomata initially as black swellings on the host thallus, breaking through the cortex, then black, pulvinate, often slightly taller than broad, strongly gelatinous, not gall-inducing, surface smooth to rugose, roundish to sometimes irregular in form, mainly 0.25–0.35 (−1) mm diam., up to 0.3 mm tall. Context hyphae thick-walled, 2.2–3.5 μm diam., clamp connections not observed; haustorial branches present, mother cells subsphaerical, 3.5–4.5 μm long, 2.5–4 μm wide, haustorial filament0.5–1 μm diam. Hymenium hyaline,containing numerous probasidia; hyphidia absent; probasidial initials clavate, proliferations occurring through the basal clamp. Basidia, when mature, 2-celled, with one transverse or oblique, exceptionally longitudinal septum, slightly constricted at the septum, (15–)17–24×6.5–10(−12) μm (excl. epibasidia), Q=(1.5–)2–3.5, often with an attenuated stalk like base of variable length (explaining the rather large variability of basidial size); epibasidia subcylindrical, up to 50 μm long (only old collapsed epibasidia measured), 2.5–4 μm diam. Basidiospores ellipsoid to subsphaerical, with a distinct apiculus, 6–8×5.5–6.5 μm, Q=1–1.3. Asexual morph: Undetermined.

Material examined: USA, Florida, Seminole Co., Little Big Econlockhatchee State Forest, along Florida Trail from entrance on Co. Rd. 426, 3.3 mi NE of Co. Rd. 419 in Oviedo, 28°41′ N, 81°10′ W, Sabal-Quercus virginiana-hardwood swamp, on Liquidambar, on Dirinaria aegialita, 10 January 1996, R. C. Harris 37673 (NY, holotype), (herb. Diederich, isotype).

Notes: Amongst the lichenicolous Tremella species with basidiomata developing on the host thallus and with 1 septate basidia, the new species is distinguished from most by the frequently stalked basidia and by the black basidiomata that are often slightly taller than broad. An undescribed species on Leptogium s. lat. studied by Diederich (1996, as ‘Tremella sp. 6’) has much shorter basidia, 11–15×8.5– 10 μm, and pale brown basidiomata. Another yet undescribed species on Anaptychia (‘Tremella sp. 5’) is distinguished by larger blackish basidiomata and slightly shorter and distinctly broader basidia, 15–19×10–15 μm. Within the species with not or rarely stalked basidia with mainly transverse or rarely oblique septa and distinct, not gall-inducing basidiomata, Tremella santessonii Diederich on Usnea is distinguished by dark reddish brown and flatter basidiomata, T. phaeographidis Diederich et al. on Phaeographis by larger basidiomata, 0.4– 0.7 mm diam.,and T. psoromicola Diederich on Psoromabya hymenium composed of a dense layer of cylindrical, septate, little ramified hyphidia intermixed with basidia (Diederich 1996). The species is not closely related to other lichenicolous Tremella species growing on Caliciales (e.g., Tremella christiansenii and T. phaeophysciae), but rather groups with species growing on Parmeliaceae, within a clade designated as clade III by Millanes et al. (2011). This relationship is not recovered with support, however, in our phylogenetic analyses. Dirinaria belongs to Caliciaceae (Wedin et al. 2002; Helms et al. 2003; Miadlikowska et al.2014) and the hosts of T. christiansenii and T. phaeophysciae belong to the Physciaceae.

Tremella dirinariae

Tremella dirinariae (NY, holotype) a Black basidiomata on thallus of Dirinaria aegialita b Hymenium with probasidium (arrow shows basal clamp), and old basidia and epibasidia (not stained) c–j Mature 1-septate basidia k–n Basidiospores o–q Haustoria. All microscopical photos in Phloxin B using DIC optics. Scale bars: a= 200 μm, b=20 μm, c–q=5 μm (scale bar in q). Photographs by P. Diederich

Tremella dirinariae (NY, holotype) a Black basidiomata on thallus of Dirinaria aegialita b Hymenium with probasidium (arrow shows basal clamp), and old basidia and epibasidia (not stained) c–j Mature 1-septate basidia k–n Basidiospores o–q Haustoria. All microscopical photos in Phloxin B using DIC optics. Scale bars: a= 200 μm, b=20 μm, c–q=5 μm (scale bar in q). Photographs by P. Diederich.