{{Short description|Species of lichen-forming fungus}} {{Use dmy dates|date=August 2025}} {{Use Oxford spelling|date=August 2025}} {{Speciesbox | image = Gabura fasciculare 92092919.jpg | image_caption = | taxon = Gabura fascicularis | authority = (L.) P.M.Jørg. (2014) | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = {{Collapsible list|bullets=on |''Lichen fascicularis'' {{au|L. (1767)}} |''Collema fasciculare'' {{au|(L.) F.H.Wigg. (1780)}} |''Parmelia fascicularis'' {{au|(L.) Ach. (1803)}} |''Enchylium fasciculare'' {{au|(L.) Gray (1821)}} |''Parmelia nigrescens'' var. ''fascicularis'' {{au|(L.) Schaer. (1842)}} |''Parmelia rupestris'' var. ''fascicularis'' {{au|(L.) Schaer. (1842)}} |''Collema rupestre'' var. ''fasciculare'' {{au|(L.) Rabenh. (1845)}} |''Collema nigrescens'' var. ''fasciculare'' {{au|(L.) Flot. (1850)}} |''Collema vespertilio'' var. ''fasciculare'' {{au|(L.) Flot. (1850)}} |''Lathagrium fasciculare'' {{au|(L.) A.Massal. (1853)}} |''Collema rupestre'' f. ''fasciculare'' {{au|(L.) Bosch (1853)}} |''Synechoblastus fascicularis'' {{au|(L.) A.L.Sm. (1918)}} |''Arctomia fascicularis'' {{au|(L.) Otálora & Wedin (2013)}} |''Collema fasciculare'' var. ''colensoi'' {{au|C.Bab. (1855)}} |''Synechoblastus aggregatus'' var. ''colensoi'' {{au|(C.Bab.) Müll.Arg. (1896)}} |''Collema aggregatum'' var. ''colensoi'' {{au|(C.Bab.) Zahlbr. (1924)}} |''Arctomia fascicularis'' var. ''colensoi'' {{au|(C.Bab.) de Lange (2017)}} |''Gabura fascicularis'' var. ''colensoi'' {{au|(C.Bab.) de Lange & M.Ford (2020)}} }} }}

'''''Gabura fascicularis''''' is a species of jelly lichen in the family Arctomiaceae. It is widely distributed, found across parts of Europe, North Africa, Asia, Australia, and New Zealand. Originally described by Carl Linnaeus in 1767, this small cushion-forming lichen grows primarily on the bark of mature broad-leaved trees such as elm and ash, preferring moist, shaded woodland habitats. The species has a distinctive gelatinous texture when wet and contains cyanobacteria that allow it to fix nitrogen from the atmosphere. Once more widespread, ''G.&nbsp;fascicularis'' has declined significantly in many regions due to the loss of old-growth trees and environmental pressures like acid rain, leading to its classification as a near-threatened species in Britain. Molecular studies have revealed that the species may actually comprise two separate groups—one in Europe and another in the Southern Hemisphere—though further research is needed to confirm this distinction.

==Taxonomy==

The species was first described by Carl Linnaeus in 1767 as ''Lichen fascicularis'' in the second part of his ''Mantissa Plantarum'', where he diagnosed it in Latin as a "gelatinous, foliose lichen with clustered, {{lichengloss|turbinate}} tubercles larger than the thallus lobes" ({{lang|la|L. foliaceus gelatinosus, tuberculis turbinatis fasciculatis fronde majoribus}}).<ref name="Linnaeus 1767"/> In his treatment Linnaeus cited Dillenius's ''Historia Muscorum'' (1741) as a source of illustration and habitat information, noting records from Sussex, England. Two sheets are preserved in the Linnaean Herbarium (LINN), neither annotated by Linnaeus himself. One of these, LINN 1273.141, was later selected as lectotype by Gunnar Degelius (1954). This specimen bears an annotation by Linnaeus's son (Carl Linnaeus the Younger), who is also named as the collector in the protologue, and was almost certainly gathered during an excursion near Stenbrohult in Småland. The choice of lectotype reflects that much of the descriptive and curatorial work on lichens in the Linnaean period was being undertaken by Linnaeus's son rather than Linnaeus himself.<ref name="Jørgensen 1994"/>

For much of the nineteenth and twentieth centuries the taxon was maintained in the genus ''Collema'', under the name ''Collema fasciculare'', on account of its gelatinous, homoiomerous thallus. Molecular evidence later showed that this placement was misleading. A three-locus phylogeny by Otálora and Wedin demonstrated that ''C.&nbsp;fasciculare'' is not part of Collemataceae or Peltigerales, but belongs in Arctomiaceae. On this basis they created the combination ''Arctomia fascicularis'' and argued that, despite a somewhat different ascoma development, the "''Fasciculare'' group" was best accommodated within Arctomiaceae; they also transferred three allied tropical species into ''Arctomia''.<ref name="Otálora & Wedin 2013"/>

Soon afterwards, Per Magnus Jørgensen reinstated the long-dormant genus ''Gabura'' and transferred the species as ''Gabura fascicularis'', recognising that it was morphologically and phylogenetically distinct from ''Arctomia'' in the strict sense. This treatment was later supported by Magain and co-authors, whose four-locus phylogeny recovered ''Gabura'' as a coherent lineage, with ''G.&nbsp;fascicularis'' sister to the ''G.&nbsp;insignis''/''G.&nbsp;borbonica'' complex. Their analyses also indicated that collections identified as ''G.&nbsp;fascicularis'' actually fall into two well-supported, geographically disjunct clades, one in Europe (Spain and Sweden) and another in the Southern Hemisphere (Chile and New Zealand). The authors recommended caution and further sampling before any formal taxonomic changes are made. In the same study ''Arctomia insignis'' and ''A.&nbsp;borbonica'' were formally transferred into ''Gabura'', narrowing ''Arctomia'' to just two species.<ref name="Magain et al. 2020"/>

At the infraspecific level, de Lange and Ford (2020) provided two new combinations under ''Gabura fascicularis'': var. ''colensoi'' (originally ''Collema fasciculare'' var. ''colensoi'' C.Bab., 1855) and var. ''microcarpa'' (originally ''Synechoblastus microcarpus'' Müll.Arg., 1882). These were effectively published in ''Index Fungorum'' in July 2020, regularising long-used varietal names with the current genus placement.<ref name="de Lange & Ford 2020"/>

==Description== thumb|right|''Gabura fasciculare'' growing on tree bark in New Zealand, showing the characteristic small, cushion-like thalli with their coarsely wrinkled, nodulose surface typical of this jelly lichen species The thallus (lichen body) forms small, rounded cushions to about 1.5&nbsp;cm across. It is crustose to small-foliose and very swollen and pulpy when hydrated, reaching about 10&nbsp;mm thick. The surface is coarsely nodulose-wrinkled and only indistinctly lobed; when present, the lobes are short, flattened, closely {{lichengloss|appressed}} and often overlapping, with tiny secondary {{lichengloss|lobules}} that arise from the wrinkles. The upper surface is dark olive-green to brown-black in the dry state, turning grey-green to olivaceous when wet, and is usually strongly ridged. Vegetative propagules are absent: there are no isidia or soredia (outgrowths or powdery patches used by many lichens for asexual dispersal).<ref name="Cannon et al. 2025"/>

Apothecia (disc-like fruiting bodies) develop from the lobules.<ref name="Cannon et al. 2025"/> Although not always abundant,<ref name="Kantvilas 1990"/> but when present the apothecia can be numerous and conspicuous, often covering the thallus surface. The {{lichengloss|discs}} are 0.8–2&nbsp;mm across, usually flat, the same colour as the thallus, and commonly bordered by a thick, somewhat wrinkled rim of thallus tissue (a {{lichengloss|thalline margin}}). The asci (spore sacs) usually contain eight spores (sometimes six). The ascospores measure 50–95 × 4.5–5&nbsp;micrometres, are divided by 9–16 cross-walls (septae), are {{lichengloss|vermiform}} or "worm-like", and lie helically twisted inside the ascus; they often taper at one or both ends and lack any surrounding gelatinous sheath.<ref name="Cannon et al. 2025"/>

==Habitat, distribution, and ecology==

''Gabura fascicularis'' is a widely distributed epiphytic lichen with a fragmented Holarctic range.<ref name="ITALIC"/> It occurs in oceanic and sub-oceanic regions of Europe and has been recorded in adjacent parts of North Africa and Asia.<ref name="Lichens of Wales"/> The species is also present in the Southern Hemisphere, having been documented in Australasia (including Australia and New Zealand) as part of its cosmopolitan distribution.<ref name="Kantvilas 1990"/>

This lichen grows primarily on the bark of old broad-leaved trees, especially those with relatively base-rich bark. In Europe, it has been found on mature elm (''Ulmus'') and ash (''Fraxinus'') trees, and occasionally on hazel (''Corylus'').<ref name="Lichens of Wales"/> It often occurs over mosses that carpet the bark or rock, and has even been recorded among mosses on calcareous rock outcrops.<ref name="Lichens of Wales"/> In the humid montane forests of Australasia, ''G.&nbsp;fascicularis'' inhabits very wet, shaded microhabitats on the lower parts of trees, such as understory branches and trunk buttresses.<ref name="Kantvilas 1990"/> Throughout its range, it shows a preference for moist, shaded sites; in Britain, it "appears to favour moist, shady" woodland habitats.<ref name="Lichens of Wales"/>

Ecologically, ''Gabura fascicularis'' is a cyanolichen that contains a filamentous cyanobacterial photobiont (''Nostoc''),<ref name="ITALIC"/> enabling it to fix atmospheric nitrogen. The lichen's occurrences are typically scattered and localized, reflecting its need for persistently humid conditions and undisturbed, mature substrates. The species was once more frequent, but ''G.&nbsp;fascicularis'' has declined in many areas due to the loss of mature host trees (such as elm populations decimated by disease) and environmental factors like acid rain.<ref name="Lichens of Wales"/><ref name="ITALIC"/> This decline has led to the species being regarded as rare or threatened in parts of its range; for instance, it is listed as a near-threatened species in Britain.<ref name="Lichens of Wales"/>

==See also== * List of lichens named by Carl Linnaeus

==References== {{Reflist|colwidth=30em|refs=

<ref name="Cannon et al. 2025">{{cite book |last1=Cannon |first1=P. |last2=Coppins |first2=B. |last3=Sanderson |first3=N. |last4=Simkin |first4=J. |year=2025 |title=Arctomiales: Arctomiaceae, including ''Arctomia'', ''Gabura'' and ''Gregorella'' |series=Revisions of British and Irish Lichens |volume=56 |page=4 |url=https://britishlichensociety.org.uk/sites/default/files/Arctomiales.pdf}}{{Open access}}</ref>

<ref name="de Lange & Ford 2020">{{cite journal |last1=de Lange |first1=P.J. |last2=Ford |first2=M. |title=Nomenclatural novelties |journal=Index Fungorum |date=2 July 2020 |issue=446}}</ref>

<ref name="ITALIC">{{cite web |last1=Nimis |first1=P.L. |last2=Martellos |first2=M. |first3=S. |last3=Conti |title=''Gabura fascicularis'' (L.) P.M. Jørg. |website=ITALIC 8.0 |date=4 December 2001 |url=https://italic.units.it/index.php?procedure=taxonpage&num=1008 |access-date=25 August 2025}}</ref>

<ref name="Jørgensen 1994">{{cite journal |last=Jørgensen |first=Per M. |title=Linnaean lichen names and their typification |journal=Botanical Journal of the Linnean Society |volume=115 |issue=4|year=1994 |pages=261–405 [309–311] |doi=10.1111/j.1095-8339.1994.tb01784.x}}</ref>

<ref name="Kantvilas 1990">{{cite journal |last=Kantvilas |first=Gintaras |title=Notes on the lichen flora of New South Wales 1. New records |journal=Telopea |volume=4 |issue=1 |year=1990 |doi=10.7751/telopea19904914 |doi-access=free |pages=19–31 |bibcode=1990Telop...4...19K }}</ref>

<ref name="Lichens of Wales">{{cite web |title=''Collema fasciculare'' |website=Lichens of Wales |publisher=British Lichen Society |url=https://wales-lichens.org.uk/species-account/collema-fasciculare |access-date=25 August 2025}}</ref>

<ref name="Linnaeus 1767">{{cite book |last=Linnaeus |first=Carl |title=Mantissa plantarum |year=1767 |page=711 |language=la |location=Stockholm |publisher=Lars Salvius |url=https://www.biodiversitylibrary.org/page/42948334}}</ref>

<ref name="Magain et al. 2020">{{cite journal |last1=Magain |first1=Nicolas |last2=Spribille |first2=Toby |last3=DiMeglio |first3=Joseph |last4=Nelson |first4=Peter R. |last5=Miadlikowska |first5=Jolanta |last6=Sérusiaux |first6=Emmanuël |title=Phylogenetic evidence for an expanded circumscription of ''Gabura'' (Arctomiaceae) |journal=The Lichenologist |volume=52 |issue=1 |year=2020 |doi=10.1017/S0024282919000471 |doi-access=free |pages=3–15 |bibcode=2020ThLic..52....3M }}</ref>

<ref name="Otálora & Wedin 2013">{{cite journal |last1=Otálora |first1=Mónica A.G. |last2=Wedin |first2=Mats |title=''Collema fasciculare'' belongs in Arctomiaceae |journal=The Lichenologist |volume=45 |issue=3 |year=2013 |doi=10.1017/S0024282912000849 |doi-access=free |pages=295–304 |bibcode=2013ThLic..45..295O }}</ref>

<ref name="Species Fungorum synonymy">{{cite web |title=GSD Species Synonymy. Current Name: ''Gabura fascicularis'' (L.) P.M. Jørg. [as 'fasciculare'], Lichenologist 46(4): 594 (2014) |url=https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=824242 |publisher=Species Fungorum |access-date=24 August 2025}}</ref>

}}

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Category:Baeomycetales Category:Lichen species Category:Lichens described in 1767 Category:Lichens of Asia Category:Lichens of Australasia Category:Lichens of Europe Category:Lichens of North Africa Category:Fungal taxa named by Carl Linnaeus