Teuvoa

The genus was circumscribed in 2013 by lichenologists Mohammad Sohrabi and Steven Leavitt with Teuvoa uxoris assigned as the type species. Teuvoa was segregated from the large genus Aspicilia (family Megasporaceae) after molecular phylogenetic analysis revealed that the Aspicilia uxoris species group formed a monophyletic clade that represented an independent lineage within the Megasporaceae.^[2] Three species were initially placed in the genus; two additional species from China were added in 2018.^[3] Teuvoa is distinguished from Aspicilia by its small ascospores and conidia (the latter measuring 5–8 μm), and the lack of secondary metabolites. The genus name honours Finnish lichenologist Teuvo Ahti, "one of the prominent lichen taxonomists of the 20th century".^[2]

The crustose thallus, or body, of Teuvoa, forms a distinctly areolate or patchy pattern. It can appear white to grey in colour and possesses a dull surface. Unlike some lichens, Teuvoa lacks cephalodia (specialised structures for nitrogen-fixing cyanobacteria) and pseudocyphellae (small pores on the lichen surface). Beneath the surface, Teuvoa has a single-layered cortex comprising paraplectenchymatous tissue, a particular type of arrangement of fungal hyphae. Its medulla, or innermost layer, is white in colour and does not turn blue when exposed to iodine (I−). The photobiont, or photosynthesising partner, in this lichen genus can be from the green alga genus Trebouxia or similar chlorococcoid genera, with the algal cells being more or less spherical in shape.^[2]

The reproductive structures of Teuvoa, the ascomata, form apothecia, cup-like structures bearing spore-producing asci. The disc of these structures ranges from black to brown-black and can be flat or occasionally concave or convex. The thalline margin surrounding the disc is elevated and matches the colour of the thallus. The exciple, or external tissue of the ascomata, is thin and can be stained by iodine (I+).^[2]

Internally, the epihymenium, the top layer of the hymenium (spore-bearing tissue), presents a green to olive-brown colour. The subhymenium and hypothecium (layers beneath the hymenium) are colourless but turn blue when exposed to iodine (I+ blue). The asci resemble those of the genus Aspicilia, with their wall and apical dome not turning blue when iodine is applied (I−), while their outer coat does (I+ blue). The ascospores are simple, colourless, and can be spherical to ellipsoid in shape. Additionally, Teuvoa forms pycnidia, small flask-shaped structures producing asexual spores or conidia, which are hyaline (translucent), simple, and tend to be more or less straight.^[2]

Species in this genus do not react with common chemical spot tests. Moreover, no secondary metabolites (lichen products) that are often important for lichen identification, have been detected in Teuvoa.^[2]

Teuvoa is distinct from Aspicilia due to its smaller ascospore and conidia size, measuring 5–8 μm, and the lack of secondary metabolites It also differs from the genus Lobothallia, in that it does not have lobate, radiating thalli, a subhypothecial algal layer, or certain secondary metabolites, and it grows on organic substrates such as bark, wood, and dead plant debris. Teuvoa also stands apart from Aspicilia subgenus Pachyothallia due to its absence of a subhypothecial algal layer, lecanoroid apothecia, certain secondary metabolites, and its different ecological amplitude, growing on organic substrates.^[2]