Tephromela Pertusarioides

''Tephromela'' is a genus of lichens in the family Tephromelataceae. There are about 50 species in this widespread genus. The genus was established in 1929 by the French lichenologist Maurice Choisy, who separated these species from the broader genus ''Lecanora'' based on their distinctive straight asexual spores and dark violet spore-bearing layers. These rock and bark-dwelling lichens are characterized by their white to pale grey crusty growth and black -shaped reproductive structures with purple-tinted interiors.

Taxonomy

The genus was circumscribed in 1929 by the French lichenologist Maurice Choisy. He assigned '' Tephromela atra'' as the type species. In his original description, Choisy established ''Tephromela'' to accommodate species that had previously been classified under ''Lecanora'' but had distinctive characteristics that set them apart from the core ''Lecanora'' group. Specifically, he recognized that ''Lecanora atra'' (originally described by Acharius) represented a distinct evolutionary line within what was then broadly conceived as the family Lecanoraceae.
Choisy characterized the new genus by its consistently straight (asexual spores) and its entirely black-violet hymenium (the spore-bearing layer), features that distinguished it from other ''Lecanora'' species. He noted that this species had previously been known as ''Patellaria tephromelas'' in earlier literature, reflecting its distinctive dark colouration. The genus name ''Tephromela'' itself references this characteristic dark pigmentation.

This taxonomic decision was part of Choisy's broader systematic revision of the Lecanoraceae, in which he argued for subdividing the artificially broad genus ''Lecanora'' into smaller, more natural groups based on detailed morphological and reproductive characters. His approach emphasized the taxonomic importance of previously overlooked features like pycnoconidia structure and hymenium coloration in establishing evolutionary relationships within lichen-forming fungi.

Description

''Tephromela'' lichens form crusts that adhere firmly to the rock or bark they colonise. The surface is usually white to pale grey and may look glossy, cracked into tiny angular islands () or dotted with low warts; dark grey–black powdery soredia sometimes blanket the thallus and mute its base colour. A thin, dark line is occasionally visible between the areoles, marking where the colony advances. Microscopy reveals a layer of green algal cells 6–18 Î¼m across (the ) embedded in a colourless fungal medulla that shows no iodine staining reaction (I–).

Reproductive bodies appear as black discs (apothecia) that begin sunken in the crust but soon sit flush or slightly raised. Each retains a rim of thallus tissue (the ), while the —the inner cup wall found in many other lichens—is reduced to a thin, often barely perceptible layer. Chemical pigments give the spore-bearing layer a lilac to purple colour that turns bright red in a drop of sodium hypochlorite (the N test); a similar hue coats the tops of the slender paraphyses that thread the hymenium. Beneath lies a pale ochre to brown . Asci are of the ''Bacidia''-type and contain eight colourless ascospores that are ellipsoid, lack cross-walls (septa and have comparatively thick walls but no outer gelatinous sheath.

Minute flask-shaped pycnidia embedded in the crust release straight, colourless conidia that range from stubby rods to fine threads. Chemically the genus is varied: many species deposit atranorin or lichexanthone in the cortex and store an assortment of depsidone acids in the medulla. ''Tephromela'' is distinguished from superficially similar genera by its persistent thalline margin, purple-violet hymenium, poorly developed exciple, ''Bacidia''-type asci and chain-forming conidiogenous cells.

Species

*'' Tephromela alectoronica''
*'' Tephromela antarctica''
*'' Tephromela arafurensis''
*'' Tephromela atra''
*'' Tephromela atrocaesia''
*'' Tephromela atroviolacea''
*'' Tephromela austrolitoralis''
*'' Tephromela baudiniana'' – Australia
*'' Tephromela bourgeanica''
*'' Tephromela buelliana''
*'' Tephromela bullata''
*'' Tephromela bunyana''
*'' Tephromela connivens''
*'' Tephromela disciformis''
*'' Tephromela disjuncta''
*'' Tephromela erosa''
*'' Tephromela eviolacea''
*'' Tephromela follmannii''
*''Tephromela gigantea''
*'' Tephromela globularis''
*'' Tephromela granularis''
*'' Tephromela grumosa''
*'' Tephromela immersa''
*'' Tephromela isidiosa''
*'' Tephromela korundensis''
*'' Tephromela lignicola'' – Falkland Islands
*'' Tephromela lillipillensis''
*'' Tephromela lirellina''
*'' Tephromela lucifraga''
*'' Tephromela lucifuga''
*'' Tephromela matogrossensis''
*'' Tephromela minor''
*'' Tephromela neobunyana''
*'' Tephromela nothofagi'' – Australia
*'' Tephromela olivetorica''
*'' Tephromela pacifica''
*'' Tephromela parasitica''
*'' Tephromela pertusarioides''
*'' Tephromela physodica''
*'' Tephromela priestleyi''
*'' Tephromela promontorii''
*'' Tephromela rhizophorae''
*'' Tephromela rimosula''
*'' Tephromela skottsbergii''
*'' Tephromela sorediata''
*'' Tephromela stenosporonica''
*'' Tephromela superba''
*'' Tephromela territoriensis''
*'' Tephromela variabilis''

References

{{Taxonbar, from=Q10693140

Lecanorales
Lecanorales genera
Lichen genera
Taxa described in 1929
Taxa named by Maurice Choisy