Vezdaea
Vezdaea is a genus of crustose lichens in the monotypic family Vezdaeaceae, which itself is the only taxon in the order Vezdaeales. The genus was established in 1976 and named after the Czech lichenologist Antonín Vězda for his contributions to lichen science. These lichens form extremely thin crusts that appear as dustings of tiny greenish to grey particles on decaying moss, plant debris, and soil, particularly in metal-enriched environments that other lichens avoid. The genus contains 14 species.
Taxonomy
The genus was circumscribed by Elisabeth Tschermak-Woess and Josef Poelt in 1976. The genus name honours the Czech lichenologist Antonín Vězda.The family name Vezdaeaceae was originally proposed by Poelt and Vězda in 1981; the proposal, however, did not meet the formal requirements of the International Code of Nomenclature: Poelt and Vězda omitted a Latin description and did not designate the type genus, so under Articles 32.1 and 36.1 the name was not validly published. The family was later publisher validly by John Charles David and David Hawksworth in 1991. The order Vezdaeales was published by H. Thorsten Lumbsch and Robert Lücking in 2016 to accommodate the isolate family Vezdaeaceae and its single genus.
Description
Vezdaea forms an extremely thin crust that appears as a dusting of minute, grain-like greenish to grey particles on its chosen substrate. Each particle is a —a tight ball of algal cells wrapped in a thin fungal jacket—which gives the thallus a powdery look rather than a continuous skin. Colonies may begin hidden under the surface layers of decaying leaves, moss tissue or even beneath the of other lichens, but they usually break through and develop on the surface as they mature. The photosynthetic partner is from the filamentous green algal genus Leptosira. No specialised vegetative propagules have been recorded, and thin-layer chromatography has failed to detect any characteristic lichen products.The sexual structures are tiny half-sphere to top-shaped apothecia that remain almost invisible when dry in most species. They lack both a true outer wall and the supporting tissue found in many lichens, leaving the spore-bearing layer exposed once the apothecia swell with moisture. That layer is threaded with branched paraphyses which can clasp and intertwine around the spore sacs if well developed. The asci themselves resemble those of genus Pertusaria: eight-spored, cylindrical, with thick walls and a strongly blue staining reaction to potassium iodide except for a tiny apical pore. Their colourless ascospores vary from simple one-celled bodies to multi-septate forms, and may have smooth or slightly warted surfaces. Asexual reproduction is poorly understood; conventional pycnidia have not been seen, but some hyphae bear cells that bud off colourless, rod-shaped spores.