# Gallaicolichen

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Single-species fungal genus

Gallaicolichen Scientific classification Kingdom: Fungi Division: Ascomycota Class: Lecanoromycetes Order: Gyalectales Family: Porinaceae Genus: Gallaicolichen Sérus. & Lücking (2007) Species: G. pacificus Binomial name Gallaicolichen pacificus Serux. & Lücking (2007)

***Gallaicolichen*** is a fungal [genus](/source/Genus) that contains the single species ***Gallaicolichen pacificus***, a [foliicolous](/source/Foliicolous_lichen) (leaf-dwelling) [lichen](/source/Lichen). Originally discovered in Hawaii in 2007, *G. pacificus* has since been found in various locations across the Pacific, including Australia, [New Caledonia](/source/New_Caledonia), [Vanuatu](/source/Vanuatu), the Philippines, and Japan. The lichen forms small, pale greenish-yellow to yellowish-grey patches on leaves, typically in mid-altitude forests and along forest edges. *G. pacificus* is notable for its unique reproductive structures called [peltidiangia](/source/Glossary_of_lichen_terms#peltidiangia), which produce disc-shaped [propagules](/source/Propagule) (peltidia) for [asexual reproduction](/source/Asexual_reproduction). Initially, its taxonomic classification was [uncertain](/source/Incertae_sedis),[1] but recent discoveries of specimens with sexual reproductive structures ([perithecia](/source/Glossary_of_lichen_terms#perithecia)) have enabled scientists to confidently place it within the family [Porinaceae](/source/Porinaceae).

## Taxonomy

The [type specimen](/source/Type_(biology)) of *Gallaicolichen pacificus* was originally collected from Kolukola Park in [Hamakua](/source/Hamakua), [Hawaii](/source/Hawaii), where it was found growing on *[Syzygium cumini](/source/Syzygium_cumini)*. The genus name honours the New Zealander botanist and lichenologist [David Galloway](/source/David_Galloway_(botanist)). Both the genus and its species were proposed in 2007 by [Emmanuël Sérusiaux](/source/Emmanu%C3%ABl_S%C3%A9rusiaux) and [Robert Lücking](/source/Robert_L%C3%BCcking).[2]

Initially, the taxonomic placement of *G. pacificus* within the Ascomycota was uncertain due to the absence of ascomata and lack of molecular data. However, the discovery of fertile specimens in [New Caledonia](/source/New_Caledonia), producing both [peltidiangia](/source/Glossary_of_lichen_terms#peltidiangia) and [perithecia](/source/Glossary_of_lichen_terms#perithecia), along with [molecular](/source/Molecular_phylogenetics) analysis using the [mitochondrial small subunit ribosomal](/source/Mitochondrial_ribosome) RNA (mtSSU) marker, has confirmed its placement within the family [Porinaceae](/source/Porinaceae). Phylogenetic analysis reveals that *G. pacificus* is closely related to *[Porina guianensis](https://en.wikipedia.org/w/index.php?title=Porina_guianensis&action=edit&redlink=1)*.[3]

## Description

*Gallaicolichen pacificus* is characterised by its leaf-dwelling, [epiphyllous](/source/Glossary_of_lichen_terms#epiphyllous) thallus, which appears as pale greenish yellow to pale yellowish grey rounded patches, ranging from 0.5 to 1.7 mm in diameter. The edges of these patches are slightly lobed, and the surface is typically smooth and somewhat shiny, becoming more intricate when examined closely. The thallus is relatively thin, measuring up to 20 [μm](/source/Micrometre), and comprises an interlaced network of fungal filaments ([hyphae](/source/Hypha)) and large, organized algal cells that form the lichen's [photosynthetic](/source/Photosynthesis) component, known as the [photobiont](/source/Glossary_of_lichen_terms#photobiont). Within the mature regions of the thallus, sizeable [oxalate](/source/Oxalate) crystals are found, which diminish in number towards the edges.[2]

Occasionally, a layer known as the [cortex](/source/Cortex_(botany)) is present, which may or may not be fully developed, made of a single layer of blocky or multi-sided cells that sometimes have a slightly brownish tinge. Surrounding the thallus is the [prothallus](/source/Prothallus#In_lichens), a typically colourless, algae-free membranous layer that may sometimes appear bluish or brownish. The photobiont of this species is a type of alga from the genus *[Phycopeltis](/source/Phycopeltis)*, belonging to the family [Trentepohliaceae](/source/Trentepohliaceae). The algal cells are greenish-brown, measuring roughly 8 to 11 by 4 to 5 μm, and are neatly arranged in radial rows forming plates.[2]

Structures reminiscent of [goniocystangia](/source/Glossary_of_lichen_terms#goniocystangia), termed [peltidiangia](/source/Glossary_of_lichen_terms#peltidiangia) by the authors, are consistently present, with each thallus patch containing 1 to 8 of these structures. These peltidiangia begin to develop at the centre of the patch and are almost perfectly circular, featuring a relatively thick, upright margin that is white and composed of raised hyphae that are not fused together. This margin is typically enveloped by the thallus.[2]

The reproductive [propagules](/source/Propagule) of *Gallaicolichen pacificus*, referred to as [peltidia](/source/Glossary_of_lichen_terms#peltidia), are numerous and fill the cavity of the peltidiangia. These [propagules](/source/Propagule) are disc-shaped, around 25 to 55 μm in diameter and 10 to 15 μm thick, with a regular arrangement. They consist of branching cells from the photobiont *Phycopeltis*, which are linked to a central, root-like structure and curled inward on the other side, surrounding a small, orderly layer of fungal cells. Typically, one to two ends of fungal filaments are found between the branches of the algal cells and are visibly apparent on the outer surface of the propagules. The ends of the algal branches are slightly enlarged and have a shiny appearance.[2]

Perithecia, which are fruiting bodies used for spore production, were previously unknown in this species but have now been observed in some specimens. They are solitary and scattered, shaped like half-spheres to almost complete spheres, measuring 0.2–0.3 mm across and 0.1–0.2 mm high. Their surface is smooth ([glabrous](/source/Glossary_of_lichen_terms#glabrous)), with a flat top. The [ostiole](/source/Ostiole)—a small opening through which spores are released—is located at the top but is difficult to see, marked by a pale orange area around it. The perithecia are coated with a layer of yellowish crystals made of [calcium oxalate](/source/Calcium_oxalate), 30–45 μm thick. On top of that is a thin 15–20 μm layer of tissue containing algae (algiferous tissue), which helps with [photosynthesis](/source/Photosynthesis). The involucrellum (a protective outer layer) is fused with the [excipulum](/source/Glossary_of_lichen_terms#excipulum) (the wall of the fruiting body), and both are densely covered with smaller crystals measuring 10–15 μm thick.[3]

The [hamathecium](/source/Glossary_of_lichen_terms#hamathecium) refers to sterile filaments that support the developing spores. In this case, the hamathecium is colourless ([hyaline](/source/Hyaline)) and lacks any scattered [granules](/source/Glossary_of_lichen_terms#granules) (non-inspersed). It consists of simple, unbranched filaments ([paraphyses](/source/Paraphyses)), which are 1–1.5 μm wide. The [asci](/source/Ascus), which are sac-like structures that contain the spores, are narrow and shaped like a slightly clubbed cylinder ([obclavate](/source/Glossary_of_lichen_terms#obclavate)). These asci do not react to [iodine](/source/Iodine) stains (I−) and measure about 92.5 by 12 μm. The top of the ascus is slightly flat, with a small ring structure. Each ascus holds eight spores, which are spindle-shaped ([fusiform](/source/Glossary_of_lichen_terms#fusiform)), divided into 6–7 compartments ([septate](/source/Septum)), and measure 24.5–28 μm in length and 4–5.5 μm in width. The spores are 4–7 times as long as they are wide, colourless, and are surrounded by a gelatinous sheath that is about 3.5 μm thick.[3]

Specimens can have both peltidiangia and perithecia, although this is uncommon. When perithecia are present, peltidiangia are typically reduced.[3]

## Habitat and distribution

In addition to the [type locality](/source/Type_locality_(biology)) in Hawaii, *Gallaicolichen pacificus* has been recorded from [Queensland](/source/Queensland), Australia, [New Caledonia](/source/New_Caledonia), [Vanuatu](/source/Vanuatu),[2] the Philippines,[4] and Japan (Ryukyu Islands).[5]

In New Caledonia, *G. pacificus* has been observed in several locations in the South and North Provinces of [Grande Terre](/source/Grande_Terre_(New_Caledonia)). It is found in high numbers on [phorophytes](/source/Phorophyte) in forests at mid-altitude (150–600 m elevation), as well as along forest edges and in [riparian](/source/Riparian) habitats.[3] The majority of specimens exhibit only peltidiangia without ascomata, with the occurrence of both perithecial ascomata and peltidiangia on the same thallus being uncommon.[3]

## References

1. **[^](#cite_ref-Wijayawardene_et_al._2022_1-0)** Wijayawardene, N.N.; Hyde, K.D.; Dai, D.Q.; Sánchez-García, M.; Goto, B.T.; Saxena, R.K.; et al. (2022). ["Outline of Fungi and fungus-like taxa – 2021"](https://www.researchgate.net/publication/358798332). *Mycosphere*. **13** (1): 53–453 [241]. [doi](/source/Doi_(identifier)):[10.5943/mycosphere/13/1/2](https://doi.org/10.5943%2Fmycosphere%2F13%2F1%2F2). [hdl](/source/Hdl_(identifier)):[10481/76378](https://hdl.handle.net/10481%2F76378).

1. ^ [***a***](#cite_ref-Sérusiaux_&_Lücking_2007_2-0) [***b***](#cite_ref-Sérusiaux_&_Lücking_2007_2-1) [***c***](#cite_ref-Sérusiaux_&_Lücking_2007_2-2) [***d***](#cite_ref-Sérusiaux_&_Lücking_2007_2-3) [***e***](#cite_ref-Sérusiaux_&_Lücking_2007_2-4) [***f***](#cite_ref-Sérusiaux_&_Lücking_2007_2-5) Sérusiaux, E.; Lücking, R. (2007). "*Gallaicolichen*, a new genus of foliicolous lichen with unique diaspores". In Kärnefelt, Ingvar; Thell, Arne (eds.). *Lichenological Contributions in Honour of David Galloway*. Bibliotheca Lichenologica. Vol. 95. Berlin/Stuttgart: J. Cramer. pp. 509–516. [ISBN](/source/ISBN_(identifier)) [978-3-443-58074-2](https://en.wikipedia.org/wiki/Special:BookSources/978-3-443-58074-2).

1. ^ [***a***](#cite_ref-Lebreton_et_al._2024_3-0) [***b***](#cite_ref-Lebreton_et_al._2024_3-1) [***c***](#cite_ref-Lebreton_et_al._2024_3-2) [***d***](#cite_ref-Lebreton_et_al._2024_3-3) [***e***](#cite_ref-Lebreton_et_al._2024_3-4) [***f***](#cite_ref-Lebreton_et_al._2024_3-5) Lebreton, Elise; Ertz, Damien; Lücking, Robert; Simon, Antoine; Smith, Clifford; Sérusiaux, Emmanuël (2024). "Further expansion of morphological variability in the Porinaceae (Ascomycota, Ostropales) with the placement of the enigmatic genus *Gallaicolichen*". *The Lichenologist*. **56** (2–3): 61–71. [doi](/source/Doi_(identifier)):[10.1017/S0024282924000124](https://doi.org/10.1017%2FS0024282924000124).

1. **[^](#cite_ref-Grant_et_al._2022_4-0)** Grant, S.; Webbink, K.; von Konrat, M.; Lumbsch, H.T.; Gaswick, W. (2022). ["Field Museum of Natural History (Botany) Lichen Collection"](https://doi.org/10.15468/sc258x). Field Museum, Chicago. [doi](/source/Doi_(identifier)):[10.15468/sc258x](https://doi.org/10.15468%2Fsc258x). Retrieved 18 October 2023.

1. **[^](#cite_ref-Miyazawa_et_al._2022_5-0)** Miyazawa, Kento; Ohmura, Yoshihito; Yamaoka, Yuichi (2022). ["Noteworthy foliicolous lichens collected from Iriomote Island, southern Japan"](https://www.researchgate.net/publication/358090353). *Taiwania*. **67** (1): 155‒163. [doi](/source/Doi_(identifier)):[10.6165/tai.2022.67.155](https://doi.org/10.6165%2Ftai.2022.67.155).

Taxon identifiers Gallaicolichen pacificus Wikidata: Q5518854 Wikispecies: Gallaicolichen pacificus AusLichen: 30017633 GBIF: 2590211 IndexFungorum: 528976 MycoBank: 528976 Open Tree of Life: 4094128 SpeciesFungorum: 528976

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