# Saxiloba firmula

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Species of lichen

Saxiloba firmula Scientific classification Kingdom: Fungi Division: Ascomycota Class: Lecanoromycetes Order: Gyalectales Family: Porinaceae Genus: Saxiloba Species: S. firmula Binomial name Saxiloba firmula (Müll.Arg.) Lücking, Moncada & Sipman (2020) Synonyms[2] Porina firmula Müll.Arg. (1885) Verrucaria firmula (Müll.Arg.) Nyl. (1892)[1]

***Saxiloba firmula*** is a species of [placodioid](/source/Glossary_of_lichen_terms#placodioid) [saxicolous lichen](/source/Saxicolous_lichen) in the family [Porinaceae](/source/Porinaceae).[3] This lichen is native to the Caribbean, where it grows on [calcareous](/source/Calcareous) rocks in shaded or semi-exposed habitats. Known for its distinctive [rosette-like](/source/Rosette_(botany)) thallus with surface patterns, *S. firmula* exemplifies the [morphological](/source/Morphology_(biology)) and ecological adaptations characteristic of the genus *[Saxiloba](/source/Saxiloba)*, for which it is the [type species](/source/Type_species).

## Taxonomy

*Saxiloba firmula* was originally [described](/source/Species_description) in 1872 by the Swiss lichenologist [Johannes Müller Argoviensis](/source/Johannes_M%C3%BCller_Argoviensis) as *Porina firmula*.[4] In 2020, [Robert Lücking](/source/Robert_L%C3%BCcking), Bibiana Moncada, and [Harrie Sipman](/source/Harrie_Sipman) transferred the species to the newly created genus *[Saxiloba](/source/Saxiloba)* based on its unique [placodioid](/source/Glossary_of_lichen_terms#placodioid) thallus [morphology](/source/Morphology_(biology)) and [molecular phylogenetics](/source/Molecular_phylogenetics) evidence. The genus was established to separate species with this morphology from other members of the family [Porinaceae](/source/Porinaceae).[5]

## Description

*Saxiloba firmula* has a flattened, leaf-like [thallus](/source/Thallus) that forms tightly appressed [rosettes](/source/Rosette_(botany)) measuring 10–20 mm in diameter. The edges of the thallus feature distinct lobes, and its surface is marked by a network of fine, reticulate lines. These lines define chambers within the thallus that contain clusters of crystals, giving the lichen a textured appearance when wet. The colour of the thallus ranges from silvery grey-green to olive-grey.[5]

The internal structure of *S. firmula* is complex, with a tightly packed fungal layer forming the upper cortex. Beneath this is the [photobiont layer](/source/Glossary_of_lichen_terms#photobiont_layer), which contains symbiotic [green algae](/source/Green_algae) of the genus *[Trentepohlia](/source/Trentepohlia_(alga))*. Embedded within the photobiont layer are large crystal clusters, thought to play a role in light management. A loosely arranged [medulla](/source/Medulla_(lichenology)) of fungal [hyphae](/source/Hypha) underlies the photobiont layer, and a dark [hypothallus](/source/Glossary_of_lichen_terms#hypothallus) anchors the lichen to its rocky [substrate](/source/Glossary_of_lichen_terms#substrate).[5]

Reproductive structures include [perithecia](/source/Perithecia), which are immersed in the thallus and covered by a layer of fungal tissue. The reddish-brown to cherry-red [ostioles](/source/Ostiole) (openings) of the perithecia are visible on the surface. The [asci](/source/Ascus) within produce small, colourless, multi-septate [ascospores](/source/Glossary_of_lichen_terms#ascospores).[5]

## Habitat and distribution

*Saxiloba firmula* is found in the Caribbean, including Cuba, [Isla de la Juventud](/source/Isla_de_la_Juventud) (formerly Isle of Pines), [Puerto Rico](/source/Puerto_Rico), and the [Bahamas](/source/Bahamas). It primarily grows on [calcareous](/source/Calcareous) rocks in dry forest habitats, favouring shaded or semi-shaded conditions. Despite its preference for shade, it can tolerate limited sun exposure, allowing it to inhabit a range of microhabitats.[5]

The species' vertical arrangement of crystal clusters and algal cells within its thallus may enhance its ability to capture and utilise light in low-light environments. This adaptation likely contributes to its success in the often dim, shaded habitats it occupies.[5]

## References

1. **[^](#cite_ref-Hue_1892_1-0)** Hue, A. (1892). "Lichenes exoticos". *Nouvelles Archives du Museum d'Histoire Naturelle*. **4**: 103–156.

1. **[^](#cite_ref-Species_Fungorum_synonymy_2-0)** ["GSD Species Synonymy. Current Name: *Saxiloba firmula* (Müll. Arg.) Lücking, B. Moncada & Sipman, in Lücking, Moncada, Sipman, Sobreira, Viñas, Gutíerrez & Flynn, Plant and Fungal Systematics 65(2): 580 (2020)"](https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=835481). [Species Fungorum](/source/Species_Fungorum). Retrieved 7 January 2025.

1. **[^](#cite_ref-CoL_3-0)** ["*Saxiloba firmula* (Müll. Arg.) Lücking, B. Moncada & Sipman"](https://www.catalogueoflife.org/data/taxon/B2N7K). *[Catalogue of Life](/source/Catalogue_of_Life)*. [Species 2000](/source/Species_2000): Leiden, the Netherlands. Retrieved 7 January 2025.

1. **[^](#cite_ref-Müller_1885_4-0)** Müller, J. (1885). "Pyrenocarpeae Cubenses a cl. C. Wright lectae". *Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie* (in Latin). **6**: 375–421.

1. ^ [***a***](#cite_ref-Lücking_et_al._2020_5-0) [***b***](#cite_ref-Lücking_et_al._2020_5-1) [***c***](#cite_ref-Lücking_et_al._2020_5-2) [***d***](#cite_ref-Lücking_et_al._2020_5-3) [***e***](#cite_ref-Lücking_et_al._2020_5-4) [***f***](#cite_ref-Lücking_et_al._2020_5-5) Lücking, Robert; Moncada, Bibiana; Sipman, Harrie (2020). ["*Saxiloba*: a new genus of placodioid lichens from the Caribbean and Hawaii shakes up the Porinaceae tree (lichenized Ascomycota: Gyalectales)"](https://doi.org/10.35535%2Fpfsyst-2020-0031). *Plant and Fungal Systematics*. **65** (2): 577–585. [doi](/source/Doi_(identifier)):[10.35535/pfsyst-2020-0031](https://doi.org/10.35535%2Fpfsyst-2020-0031).

Taxon identifiers Porina firmula Wikidata: Q108282363 GBIF: 5475875 IndexFungorum: 402065 MycoBank: 402065 SpeciesFungorum: 402065

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Adapted from the Wikipedia article [Saxiloba firmula](https://en.wikipedia.org/wiki/Saxiloba_firmula) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Saxiloba_firmula?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.