# Ahtiana

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***Ahtiana*** is a fungal [genus](/source/Genus) in the family [Parmeliaceae](/source/Parmeliaceae). A [monotypic](/source/Monotypic) genus, it contains the single species ***Ahtiana sphaerosporella***, the **mountain candlewax lichen**,[1] found in western North America. The species was originally classified as *Parmelia sphaerosporella* by [Johannes Müller Argoviensis](/source/Johannes_M%C3%BCller_Argoviensis) in 1891, before [Trevor Goward](/source/Trevor_Goward) established the new genus *Ahtiana* in 1985, naming it after Finnish lichenologist [Teuvo Ahti](/source/Teuvo_Ahti). This foliose lichen is characterised by its pale yellowish-green [thallus](/source/Thallus), spherical [spores](/source/Spore), laminal [apothecia](/source/Apothecia) (fruiting bodies), and the presence of [usnic](/source/Usnic_acid) and [caperatic acids](/source/Caperatic_acid). It primarily grows on the bark of [whitebark pine](/source/Pinus_albicaulis) in [subalpine](/source/Subalpine) and [montane](/source/Montane) regions, though it occasionally colonises other [conifers](/source/Conifer) outside its preferred host's range.

## Taxonomy

The genus *Ahtiana* was established in 1985 by [Trevor Goward](/source/Trevor_Goward) to accommodate the species *Ahtiana sphaerosporella*, previously classified as *Parmelia sphaerosporella* by [Johannes Müller Argoviensis](/source/Johannes_M%C3%BCller_Argoviensis) in 1891. Goward's reclassification was prompted by notable morphological and chemical differences between *A. sphaerosporella* and other members of the genus *[Parmelia](/source/Parmelia_(fungus))*. The name *Ahtiana* honours the Finnish lichenologist [Teuvo Ahti](/source/Teuvo_Ahti), renowned for his contributions to the study of western North American lichens.[2]

Historically, *Parmelia sphaerosporella* was considered part of the broad genus *Parmelia*, which has since been divided into numerous smaller genera. While some earlier taxonomic studies emphasized its similarity to *Parmelia* sect. *Cyclocheila* (now *[Pseudoparmelia](/source/Pseudoparmelia)*), subsequent analyses highlighted fundamental distinctions, such as its spore shape, cortical structure, and [secondary chemistry](/source/Secondary_metabolism). These features, particularly its spherical spores and production of [caperatic acid](/source/Caperatic_acid), indicated a closer relationship with lichens than with the group.[2]

Despite sharing some superficial traits with other cetrarioid genera, such as *[Nephromopsis](/source/Nephromopsis)*, *Ahtiana* differs in its closely appressed foliose thallus, laminal [apothecia](/source/Apothecia), and emergent [pycnidia](/source/Pycnidia). These distinctive characteristics, coupled with its unique chemical profile, justify its placement in a separate monotypic genus within the family Parmeliaceae.[2]

In 2017, Pradeep Divakar and colleagues applied a recently developed "temporal phylogenetic" method to define time-based thresholds for taxonomic ranks within the family Parmeliaceae. According to their analysis, groups of species that [diverged](/source/Evolutionary_divergence) between 29.45 and 32.55 million years ago were proposed to represent genera. As part of their findings, they suggested [synonymizing](/source/Synonym_(taxonomy)) *Arctocetraria* with *[Nephromopsis](/source/Nephromopsis)*, along with several other Parmelioid genera, to ensure that all genera within the family were of similar evolutionary age.[3] While some of their proposed taxonomic revisions gained acceptance, a subsequent critical review of the temporal phylogenetic approach for fungal classification rejected the synonymisation of the Parmelioid genera with *Nephromopsis*.[4]

It had been suggested that the genus include *A. aurescens* (**Eastern candlewax lichen**,[1] formerly *Cetraria aurescens* Tuck.) and *A. pallidula* (**pallid candlewax lichen**,[1] formerly *Cetraria pallidula* Tuck.) based on similarities in [morphology](/source/Morphology_(biology)),[5] but this transfer is not supported by [molecular analysis](/source/Molecular_phylogenetics).[6]

## Description

The genus *Ahtiana* includes [foliose lichens](/source/Foliose_lichen), meaning they have a leaf-like structure that closely adheres to their . The [thallus](/source/Thallus), or main body, is pale yellowish-green, occasionally darkening to an olivaceous hue, and often has a wrinkled or folded surface texture. The undersides are typically pale tan to olive and feature sparse to abundant [rhizines](/source/Rhizine)—root-like structures that help the lichen anchor to its substrate. A key distinguishing feature of *Ahtiana* is the absence of [pseudocyphellae](/source/Pseudocyphella), which are small pores or breaks in the surface commonly seen in related genera. Instead, the upper (the lichen's outer layer) is smooth and composed of a thin, specialised tissue type known as a leptodermatous cortex.[2]

The reproductive structures are prominently laminal, meaning they occur all over the thallus surface, rather than in the centre or on the margins. [Apothecia](/source/Apothecia), the fruiting bodies that produce [spores](/source/Spore), are frequently found near the centre of the lichen and have an entire, unbroken . The spores are spherical, (non-segmented), and measure 4–6 [μm](/source/%CE%9Cm) in diameter. [Pycnidia](/source/Pycnidia), small flask-shaped structures producing asexual spores, are also laminal, often abundant, and conspicuous due to their dark colouration. *Ahtiana* produces characteristic chemical compounds, including [usnic acid](/source/Usnic_acid), which contributes to its yellowish colour, and [caperatic acid](/source/Caperatic_acid), an [aliphatic](/source/Aliphatic) acid identified through [thin-layer chromatography](/source/Thin-layer_chromatography).[2]

## Habitat, distribution, and ecology

*Ahtiana sphaerosporella* is exclusively found in western North America, where it inhabits [subalpine](/source/Subalpine) and [montane](/source/Montane) regions. It has a strong ecological preference for the bark of *[Pinus albicaulis](/source/Pinus_albicaulis)* (whitebark pine), often forming abundant [colonies](/source/Colony_(biology)) on this tree. However, it is absent from nearby trees of other species in its typical range. In certain areas outside the range of *Pinus albicaulis*, such as the [Northwest Territories](/source/Northwest_Territories), it has been observed on other conifers, including *[Abies lasiocarpa](/source/Abies_lasiocarpa)* (subalpine fir). The distribution of the lichen closely parallels that of its preferred host tree *P. albicaulis*, which is typically found at high elevations and, in some cases, in lower montane stands. In southern parts of its range, the lichen has been documented colonising other species of [pine](/source/Pine) and [spruce](/source/Spruce), showinfg some adaptability to alternative hosts when necessary. Reports of the lichen from outside western North America, such as a record from [Emo, Ontario](/source/Emo,_Ontario), were later identified as misidentifications.[2]

## References

1. Goward T. (1985). "*Ahtiana*, a new lichen genus in the Parmeliaceae". *Bryologist*. **88** (4): 367–71. [doi:10.2307/3242678](https://doi.org/10.2307/3242678). [JSTOR 3242678](https://www.jstor.org/stable/3242678)

1. Divakar, Pradeep K.; Crespo, Ana; Kraichak, Ekaphan; Leavitt, Steven D.; Singh, Garima; Schmitt, Imke; Lumbsch, H. Thorsten (2017). "Using a temporal phylogenetic method to harmonize family- and genus-level classification in the largest clade of lichen-forming fungi". *Fungal Diversity*. **84**: 101–117. [doi:10.1007/s13225-017-0379-z](https://doi.org/10.1007/s13225-017-0379-z)

1. Lücking, Robert (2019). "Stop the abuse of time! Strict temporal banding is not the future of rank-based classifications in fungi (including lichens) and other organisms". *Critical Reviews in Plant Sciences*. **38** (3): 199–253. [Bibcode:2019CRvPS..38..199L](https://ui.adsabs.harvard.edu/abs/2019CRvPS..38..199L). [doi:10.1080/07352689.2019.1650517](https://doi.org/10.1080/07352689.2019.1650517)

1. Thell A, Goward T, Randlane T, Kärnefelt EI, Saag A (1995). "A revision of the North American lichen genus *Ahtiana* (Parmeliaceae)". *Bryologist*. **98** (4): 596–605. [doi:10.2307/3243591](https://doi.org/10.2307/3243591). [JSTOR 3243591](https://www.jstor.org/stable/3243591)

1. Thell, A.; Högnabbaa, F.; Elix, J.A.; Feuerer, T.; Kärnefelt, I.; Myllys, L.; Randlane, T.; Saag, A.; Stenroos, S.; Ahti, T.; Seaward, M.R.D. (2009). "Phylogeny of the cetrarioid core (Parmeliaceae) based on five genetic markers". *Lichenologist*. **41** (5): 489–511. [Bibcode:2009ThLic..41..489T](https://ui.adsabs.harvard.edu/abs/2009ThLic..41..489T). [doi:10.1017/S0024282909990090](https://doi.org/10.1017/S0024282909990090). [hdl:1885/51099](https://hdl.handle.net/1885/51099)

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