Tremella pyrenulae – Facesoffungi number: FoF 1010

Tremella pyrenulae Diederich, Millanes, Wedin & Common

Index Fungorum number: IF551496 Facesoffungi number: FoF01010

Etymology: In reference to the host Pyrenula.

Holotype: Common 9170B (BR).

Lichenicolous on the thallus of Pyrenula ochraceoflavens, not gall-inducing, not causing any visible damage to the host. Known only from Florida. Sexual morph: Basidiomata pink to pale brown, pulvinate, strongly gelatinous, surface rather smooth, roundish to slightly elongate, up to 0.5×0.4 mm, up to 0.3 mm tall, when mature with a constricted base. Context hyphae thin-walled, 2–3 μm diam., clamp connections not observed; haustorial branches not observed. Hymenium hyaline, containing numerous probasidia; hyphidia absent; probasidial initials ellipsoid to rarely clavate, proliferations occurring through the basal clamp. Basidia, when mature, 2-celled, with one longitudinal septum, slightly constricted at the septum, 13–17(−19)×9.5–13 μm (excl. epibasidia), Q=1– 1.6(−2), generally without attenuated stalk-like base; epibasidia subcylindrical, at least 45 μm long, 3–6 μm
diam. Basidiospores ellipsoid to subsphaerical, with a distinct apiculus, 7–8×6.5–7.5 μm, Q=1–1.1. Asexual morph: Undetermined.

Material examined (all on Pyrenula ochraceoflavens): USA, Florida: Hernando Co., Baypoint Park at end of CR 50/550, 28°32.166′ N, 82°39.04′ W, 25 August 2011, R. Common 9170B (BR, holotype), (S, herb. Diederich, isotypes); ibid., R. Common 9165B (BR, herb. Diederich); Collier Co., Fakahatchee Strand State Park, Janes Scenic Drive, 25°58′45″ N, 81°22′15″ W, 2014, R. Common 9870Q (herb. Diederich); ibid., picnic area off US 41, 25°55′53″ N, 81°26′39″ W, 2014, R. Common 9705 K (herb. Diederich); Pinellas Co., Caladasi Island State Park, shrubs near beach, 28°02′ N, 82°49′ W, 2013, R. Common 9616A (herb. Diederich).

Notes: This species is distinguished from many lichenicolous Tremella species by the pale non-gallinducing basidiomata developing over the host thallus, and by the non-stalked basidia with one longitudinal septum. Tremella phaeographidis Diederich et al. has smaller basidiospores, 5.5–7.5×5–6 μm, longer and narrower basidia (Q=c. 2) and larger basidiomata, 0.4–0.7 mm. Tremella microcarpa Diederich and T. coccocarpiae Diederich have smaller basidiomata, rarely exceeding 0.2 mm diam., the former smaller basidia, 9.5–12.5×7– 11 μm, the latter smaller basidiospores, 5.5×4–4.5 μm. Tremella macroceratis Diederich & Hafellner and T. papuana Diederich have narrower basidiospores, 3.5– 5.5 μm broad. Tremella montis-wilhelmii Diederich and the very similar T. normandinae Diederich are both distinguished by basidia with a larger l/w ratio (Q=1.5–2) (12–17×7–9 μm in T. montis-wilhelmii, and 14.5 –21× 8.5–11.5 μm in T. normandinae), and T. montis-wilhelmii furthermore by slightly smaller basidiospores, 6–7×5– 6 μm. In our phylogeny, Tremella pyrenulae and T. graphidis form a monophyletic group. Neither the morphology, nor the host preference, however, explain this relationship. This is not surprising since previous studies have shown that morphological characters in Tremella are highly variable in closely related species, and that host switches have probably been frequent in the evolution of the group (Millanes et al. 2011, 2014).