# Llimonaea

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***Llimonaea*** is a [genus](/source/Genus) of [lichen](/source/Lichen)-forming [fungi](/source/Fungi) in the order [Arthoniales](/source/Arthoniales). The genus has been placed into the family [Opegraphaceae](/source/Opegraphaceae).[1] These lichens form thin, firmly attached [crusts](/source/Crustose_lichen) that vary from chalky white and grey to olive-green or dark brown, often edged by a neat black line and characterized by rounded or scribble-like reproductive structures that sit flush with the surface. Established as a genus in 1991, *Llimonaea* species are distinguished by their partnership with orange-tinged [green algae](/source/Green_algae), their spindle-shaped [spores](/source/Spore) with multiple [cross-walls](/source/Septum) that gradually turn brown with age, and their black-rimmed crusts with robust walls around the fruiting bodies.

## Taxonomy

Genus *Llimonaea* was [circumscribed](/source/Circumscription_(taxonomy)) by the mycologists José María Egea Fernández and Pilar Torrente in 1991. They assigned *[L. occulta](/source/Llimonaea_occulta)* as the [type](/source/Type_species), and at the time, only species of the genus.[2]

## Description

*Llimonaea* lichens form a thin, firmly attached crust ([crustose](/source/Crustose_lichen) thallus) whose surface can appear smooth or cracked and may be partially embedded in the bark or rock it [colonises](/source/Colonisation_(biology)). The crust is built from a tangled cortex of colourless fungal threads ([hyphae](/source/Hypha)) and is commonly edged by a neat black line, the , that demarcates each colony. Depending on moisture and light the thallus varies from chalky white and dove grey to olive-green or dark brown, and some species produce discrete powdery patches ([soralia](/source/Soralia)) that release bundles of algal and fungal cells for vegetative spread. The [photosynthetic](/source/Photosynthesis) partner is the orange-tinged green alga *[Trentepohlia](/source/Trentepohlia_(alga))*, although a few species live [parasitically](/source/Parasitism) on other lichens that house different algae.[3]

Reproduction is dominated by rounded or scribble-like () apothecia that sit flush with the surface and are ringed by a low rim of thallus tissue (). Beneath this margin lies a robust black wall of hyphae—the —which encloses a forest of branched, interwoven filaments () forming the . Each club-shaped [ascus](/source/Ascus) contains eight [ascospores](/source/Ascospore) and opens by splitting between its two walls ( dehiscence). When [stained](/source/Staining) with [iodine](/source/Iodine) after a mild alkaline wash, the ascus apex shows a faint blue around the tiny "window" () through which the spores escape.[3]

The spindle-shaped spores are partitioned by several thick [cross-walls](/source/Septum)—up to fourteen in some species—and gradually turn cinnamon brown with age; they often show a slight constriction at the first septum. Some *Llimonaea* species also form minute black [pycnidia](/source/Pycnidia) that ooze long, curved, colourless [conidia](/source/Conidia), providing an [asexual](/source/Asexual_reproduction) route for [dispersal](/source/Biological_dispersal). Unlike many of their roccellaceous relatives, these lichens generally lack conspicuous [secondary metabolites](/source/Secondary_metabolite); the few compounds detected fall into the [orcinol](/source/Orcinol) and β-orcinol [depside](/source/Depside) families, with [erythrin](/source/Erythrin) and [isoerythrin](/source/Isoerythrin) recorded sporadically. Collectively, the combination of a black-rimmed crust, lirelliform apothecia with a carbonised exciple, branched paraphysoids and multi-septate, late-browning spores provides a practical field diagnosis for the genus.[3]

## Species

As of June 2025, [Species Fungorum](/source/Species_Fungorum) (in the [Catalogue of Life](/source/Catalogue_of_Life)) accepts four species of *Llimonaea*:[4]

- *[Llimonaea californica](/source/Llimonaea_californica)* [5]
- *[Llimonaea flexuosa](/source/Llimonaea_flexuosa)*
- *[Llimonaea occulta](/source/Llimonaea_occulta)* [2]
- *[Llimonaea sorediata](/source/Llimonaea_sorediata)* [6]

The [taxon](/source/Taxon) *Llimonaea cerebriformis* has since been transferred to the genus *[Sparria](/source/Sparria)* as *[Sparria cerebriformis](/source/Sparria_cerebriformis)*.[7]

## References

1. Wijayawardene, Nalin N.; Hyde, Kevin D.; Lumbsch, H. Thorsten; Liu, Jian Kui; Maharachchikumbura, Sajeewa S.N.; Ekanayaka, Anusha H.; Tian, Qing; Phookamsak, Rungtiwa (2018). "Outline of Ascomycota: 2017". *Fungal Diversity*. **88** (1): 167–263. [doi:10.1007/s13225-018-0394-8](https://doi.org/10.1007/s13225-018-0394-8)

1. Torrente, P. & Egea, J.M. (1991). "*Llimonaea*, a new genus of lichenized fungi in the order Opegraphales (Ascomycotina)". *Nova Hedwigia*. **52**: 239–245.

1. Cannon, P.; Coppins, B.; Ertz, D.; Fletcher, A.; Pentecost, A.; Simkin, J. (2021). [*Arthoniales: Opegraphaceae, including the genera*Llimonaea*,*Opegrapha*,*Paralecanographa*and*Sparria'](https://britishlichensociety.org.uk/sites/default/files/Opegraphaceae.pdf)**. Vol. 13. Revisions of British and Irish Lichens. pp. 3–4.**

1. Sparrius, Laurens B. (2004). *A monograph of*Enterographa*and*Sclerophyton'**. Vol. 89. Bibliotheca Lichenologica. Berlin/Stuttgart: J. Cramer. p. 91. ISBN 978-3-443-58068-1.**

1. van den Boom, P.P.G. & Brand, A.M. (2007). ["*Llimonaea sorediata*, a new lichen (Ascomycota), widely distributed in western Europe"](https://www.researchgate.net/publication/248730168). *The Lichenologist*. **39** (4): 309–314. [Bibcode:2007ThLic..39..309V](https://ui.adsabs.harvard.edu/abs/2007ThLic..39..309V). [doi:10.1017/S0024282907006871](https://doi.org/10.1017/S0024282907006871)

1. Ertz, Damien & Tehler, Anders (2010). "The phylogeny of Arthoniales (Pezizomycotina) inferred from nucLSU and RPB2 sequences". *Fungal Diversity*. **49** (1): 47–71. [doi:10.1007/s13225-010-0080-y](https://doi.org/10.1007/s13225-010-0080-y)

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