# Marchantiana

Marchantiana is a genus of lichen-forming fungi in the family Teloschistaceae. It contains seven species of corticolous (bark-dwelling), crustose lichens that occur in the Southern Hemisphere.

## Taxonomy

Lichenologists Sergey Kondratyuk, Ingvar Kärnefelt, John Alan Elix, Arne Thell, and Jae-Seoun Hur circumscribed the genus Marchantiana in 2014, as part of a taxonomic revision of the family Teloschistaceae. They designated Marchantiana occidentalis as its type species. Initially, the genus comprised six species, all native to the Southern Hemisphere, with all but one species from Australia. The genus was named in honour of the Australian botanist Neville Graeme Marchant, to acknowledge his extensive contributions to the flora of Western Australia.
In 2023, molecular analysis using three genes suggested a close relationship between Marchantiana and Yoshimuria, and identified several new species from Patagonia. A comprehensive revision in 2024 built upon these findings, revealing that what was previously considered Marchantiana actually represents two distinct genera. While Marchantiana in the strict sense (sensu stricto) was retained for the type species M. occidentalis and related species primarily from Australia, a new genus Taedigera was established for species from southern Patagonia and New Zealand. This revision also confirmed that the genus Yoshimuria from East Asia represents a sister group to both genera. The genus Streimanniella, which was previously segregated from Marchantiana, was shown to be based on misidentified material and was synonymised with Marchantiana. Several species previously placed in Marchantiana were also found to belong in other genera – for example, M. maulensis was transferred to the genus Villophora, while M. burneyensis, M. kalbiorum and M. seppeltii were shown to belong in the subfamily Teloschistoideae.
The current circumscription recognises seven species in Marchantiana, most of which are endemic to Australia, with only M. asserigena having a wider distribution including Europe. The sister genus Taedigera contains six species found primarily in New Zealand and southern Patagonia. This geographic pattern, along with differences in secondary chemistry, supports the separation of these genera despite their morphological similarities.

## Description

Both Marchantiana and Taedigera have a crust-like thallus that can range in appearance from a continuous to a patchy texture. Its colour varies, encompassing pale grey, dark brownish-grey, dark greenish-grey, and even vibrant hues of yellow or orange. The cortical layer is often thin and arranged in a specific cellular pattern known as paraplectenchymatous. The apothecia can fall into three types: biatorine, zeorine, or lecanorine. The true exciple of these structures are made of pseudoprosoplectenchymatous tissue. Each reproductive sac, or ascus, contains eight spores that are divided into 2, 3, or 4 compartments (locules) by partitions called septa. Its conidia are rod-shaped or slightly elongated rod-shaped. The two genera are distinguished primarily by their secondary chemistry. Marchantiana species are characterised by diverse secondary metabolites, including chlorinated compounds like neochloroemodin and 5-chloroemodin, as well as depsidones like vicanicin, isofulgidin and caloploicin. In contrast, Taedigera species show simpler chemical profiles dominated by either parietin or emodin and its derivatives.
Standard chemical spot tests indicate reactions vary between species, with some showing K+ (purple) reactions in both thallus and apothecia, while others show K− reactions in the thallus but K+ (purple) in the apothecia. Some Taedigera species also show distinctive C+ (red) reactions in their apothecia.
The genera also show distinct geographic patterns, with Marchantiana species primarily occurring in warmer regions of mainland Australia, while Taedigera species are found in cooler regions of New Zealand and southern Patagonia. Both genera are primarily corticolous, growing on thin twigs and branches, though some species can occasionally be found on other substrates.

## Species

Marchantiana includes seven species of corticolous (bark-dwelling) lichens, primarily found in Australia:
* M. asserigena (Stizenb. ex J.Lahm) Søchting & Arup (2018)
* M. haematommona (Elix & S.Y. Kondr.) Søchting & Arup (2024)
* M. magnetensis (S.Y. Kondr., Elix, Kärnefelt & Kalb) Søchting & Arup (2024)
* M. michelagoensis (Elix, S.Y.Kondr. & Kärnefelt) S.Y.Kondr., Kärnefelt, A.Thell, Elix, J.Kim, A.S.Kondr. & Hur (2014)
* M. occidentalis (Elix, S.Y.Kondr. & Kärnefelt) S.Y.Kondr., Kärnefelt, Elix, A.Thell, Jung Kim, A.S.Kondr. & Hur (2014)
* M. queenslandica (Kalb, S.Y.Kondr., Elix & Kärnefelt) Arup & Søchting (2023)
* M. tasmanica Søchting (2024)

### Former species

Several species previously placed in Marchantiana have been transferred to other genera:
* Marchantiana maulensis S.Y.Kondr. et J.-S. Hur (2014) was transferred to the genus Villophora as Villophora maulensis.
* Marchantiana burneyensis, M. kalbiorum, and M. seppeltii were shown to belong in the subfamily Teloschistoideae and are no longer considered part of Marchantiana.
* Six species (M. epibrya, M. pyramus, M. ramulicola, M. subpyracea, and two newly described species) were transferred to the new genus Taedigera.