Vahliellaceae

''Vahliella'' is a genus of nine species of lichen. It is the only member of the Vahliellaceae, a family circumscribed in 2011 to contain this genus. ''Vahliella'' was formerly placed in the family Pannariaceae until molecular phylogenetics showed that it did not belong there. ''Vahliella'' species are found in the Northern Hemisphere – mainly in North America, but also in Europe and India.

''Vahliella'' species somewhat resemble those of the genus ''Fuscopannaria'' – in which they were originally classified – but are distinguished from them by the layered apical amyloid sheets of the asci, the lack of lichen acids, and the absence of an epispore.

Taxonomy

''Vahliella'' was circumscribed by Norwegian botanist Per Magnus Jørgensen in 2008. It was created to contain species formerly placed in the subgenus ''Micropannaria'' of ''Fuscopannaria'', a genus erected by Jørgensen in 1994. ''Micropannaria'' contained two species that differed mainly in the apical apparatus, where they featured amyloid sheets rather than a ring structure. At the time, Jørgensen did not believe that this distinguishing character was sufficiently different to justify these species being placed in a new genus. The type species of subgenus ''Micropannaria'', ''Fuscopannaria leucophaea'', was later shown in several phylogenetic studies to lie outside of the ''Fuscopannaria'', and also outside family Pannariaceae, which was shown to be polyphyletic. To meet the need for a new familial placement of ''Vahliella'', Mats Wedin, Jørgensen, and Stefan Ekman created the Vahliellaceae in 2011. Phylogenetically, Vahliellaceae is sister to a clade that contains Lobariaceae, Massalongiaceae, Nephromataceae, and Peltigeraceae.

The generic name ''Vahliella'' honours Norwegian botanist Martin Vahl (1749–1804), who was first to describe scientifically the type species of this genus.

Description

Family

In its Latin circumscription, Vahliellaceae is defined by its differences from the Pannariaceae: the absence of lichen acids, a poorly developed thallus excipulum, and the amyloid apical layers.

Distinctions are also made between Vahliellaceae and other closely related families, the Peltigeraceae, Nephromataceae, and Lobariaceae. Peltigeraceae has a distinctive apical tube, while Nephromataceae lacks an amyloid apical structure. Lobariaceae has an indistinct amyloid layer, dissimilar to the structure in Vahliellaceae. Massalongiaceae contains squamulose (covered with tiny scales) members that resemble the Vahliellaceae, but Massalongiaceae lack the distinct bluish-black hypothallus characteristic of some Vahliellaceae species.

Genus

''Vahliella'' species are characterized by a squamulose thallus that is typically greyish-brownish in colour. They have sessile apothecia with a variable thalline exciple, which in some apothecia is not at all developed, and with a likewise variable but always present proper margin. The hymenium is hemiamyloid (meaning it takes on a purplish-grey colour when treated with Melzer's reagent), and contains unbranched, septate paraphyses that have pigmented tips. The asci are 8-spored with sheet-like apical structures that are persistently blue-green when stained with iodine. The ascospores of ''Vahliella'' lichens are non-septate, with an ellipsoid shape; they do not have an epispore, but often have internal oil droplets.

''Vahliella'' species do not have any reactions with lichen spot tests, and do not produce secondary compounds detectable with thin layer chromatography.

Habitat and distribution

Most species of ''Vahliella'' are found in cool-temperate to arctic regions of Europe and North America, with an outlier in the mountains of India. ''Vahliella'' is a mainly saxicolous (rock-inhabiting) genus that has adapted to rather extreme habitats on maritime coasts (two species) and arctic-alpine or desert conditions. Only one species, ''V. saubinetii'', is mainly corticolous (bark-inhabiting) and tends to be more warm-temperate (Mediterranean). The most recently described species, ''Vahliella isidioidea'', grows on consolidated soil in the laurel forest of the Canary Islands.

Species

, Species Fungorum accepts nine species of ''Vahliella'':
*'' Vahliella adnata'' – India
*''Vahliella atlantica'' – Azores northwards to southwest Scandinavia
*''Vahliella californica'' – United States
*'' Vahliella globigera'' – Arctic
*'' Vahliella hookerioides'' – United States
*'' Vahliella isidioidea'' – Canary Islands
*'' Vahliella labrata'' – Channel Islands of California
*''Vahliella leucophaea'' – widespread in Northern Hemisphere
*'' Vahliella saubinetii'' – European Mediterranean region; Atlantic and Pacific coastal regions of North America

References

{{Taxonbar, from1=Q10712028, from2=Q10712033

Peltigerales genera
Lichen genera
Peltigerales
Taxa described in 2008
Taxa named by Per Magnus Jørgensen