Opeltiella

Opeltiella is a genus of lichen-forming fungi in the family Candelariaceae. The genus, established by Sergey Kondratyuk in 2020, has four species. It is differentiated from the similar genus Candelaria by its unique features such as eight-spored asci and absence of a lower and true rhizines. The genus is characterised by its to more or less  or  thallus and the unique chemical substances it contains, such as calycin, pulvinic and vulpinic acids, and pulvinic acid lactone.

Taxonomy
The genus Opeltiella was circumscribed by Ukrainian lichenologist Sergey Kondratyuk, with Opeltiella fruticans serving as the type species. Its name is derived from an anagram of the generic name Poeltia, which pays homage to Josef Poelt (1924–1995), a significant figure in the history of lichenology and a co-author of the type species of this genus. Opeltiella shares a relationship with Candelaria based on multigene molecular phylogenetics data but is distinguished by its unique features such as the lack of a lower cortical layer and true rhizines.

Multigene phylogeny data supports Opeltiella as a robust, distinct monophyletic branch, positioned separately from Candelaria, which only includes polyspored species with well-developed lower cortical layers and true rhizines. In the phylogeny derived from nuclear ribosomal internal transcribed spacer (nrITS) sequences, Opeltiella occupies a sister position to the 'Candelariella' placodizans group.

Description
Opeltiella is recognised by its to somewhat  or somewhat foliose thallus, which is irregularly incised and can range from being  to ascending or more or less erect. Its upper surface is yellow, matte, and smooth; it may lack soredia and isidia or can display a lower surface. The lower surface of the thallus is white, lacks a cortex, and ranges from being to  with a thick mat of hyphal strands. The of Opeltiella are  and its asci are 8-spored. The ascospores are to 1-septate, narrowly ellipsoid, and the conidia are ellipsoid, measuring 2.0–3.5 by 1.5 μm.

Habitat and distribution
The genus Opeltiella includes four species, with two located in South America, one in Eastern Asia, and another in North America. There is an indication that one species, Opeltiella canadensis, might be included in a different genus in the future. Opeltiella lichens can be found in various habitats, ranging from dead shrubs and cacti, sometimes cohabiting with Teloschistes hosseusianus in dry high-altitude pasture lands of about 2200 m above sea level, as well as on the bark of deciduous trees and pine trees in lowlands and coastal zones.

Species

 * Opeltiella canadensis
 * Opeltiella fibrosoides
 * Opeltiella fruticans
 * Opeltiella rubrisoli