{{Short description|Genus of lichens}} {{Use dmy dates|date=July 2025}} {{Use Oxford spelling|date=July 2025}} {{Automatic taxobox | image = | image_caption = | taxon = Orceolina | authority = Hertel (1970) | type_species = ''Orceolina kerguelensis'' | type_species_authority = (Tuck.) Hertel (1970) | subdivision_ranks = Species | subdivision = ''O. antarctica''<br /> ''O. kerguelensis'' | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = *''Urceolina'' {{au|Tuck. (1875)}} }}

'''''Orceolina''''' is a small genus of lichen-forming fungi in the family Trapeliaceae.<ref name="Wijayawardene et al. 2020"/> Established in 1970 as a replacement name for an earlier genus that was already used for flowering plants, ''Orceolina'' comprises just two species that form orange to deep red crusty patches on sun-exposed rocks. These lichens are found exclusively on the windswept subantarctic islands of the southern Indian Ocean, where they grow from sea level to alpine ridges on basaltic and granitic surfaces.

==Taxonomy==

The genus ''Orceolina'' was erected by Hannes Hertel in 1970 as a replacement name for Edward Tuckerman's 1875 ''Urceolina'',<ref name="Tuckerman 1875"/> which was pre-occupied by a flowering-plant genus. Tuckerman's original taxon, ''U.&nbsp;kerguelensis'', thus became ''Orceolina kerguelensis''. For decades the lichen had been shuffled among ''Lecanora'' and ''Placodium'' until Hertel's action clarified its status as a distinct lineage.<ref name="Poulsen et al. 2001"/> Modern checklists place ''Orceolina'' in the family Trapeliaceae.<ref name="CoL_CDS8Z"/>

Only two species are currently accepted: ''O.&nbsp;kerguelensis'' and ''O.&nbsp;antarctica''. Early molecular phylogenetics analysis showed that they form a tight clade that is sister to the southern-hemisphere {{lichengloss|placodioid}} genus ''Placopsis'', and together those two genera are sister to ''Trapelia''. The evolutionary relationships indicate that the genus' simplified spore-bearing structure evolved by becoming reduced from a ''Trapelia''-type ancestor rather than being an original primitive feature.<ref name="Poulsen et al. 2001"/> The species ''Ducatina umbilicata'', described from the Crozet and Kerguelen Islands, is closely related to ''Orceolina''; it is differentiated by its morphology (it has a large {{lichengloss|umbilicate}} thallus) and lack of secondary metabolites.<ref name="Ertz et al. 2017"/>

==Description==

''Orceolina'' species are rock-dwelling (saxicolous) crustose lichens whose thalli spread as irregular orange to deep red patches. The surface is variously cracked into wart-like or lobed units, a pattern termed {{lichengloss|verrucose}}-{{lichengloss|areolate}} or {{lichengloss|effigurate}}. Each patch is dominated by a thick outer skin ({{lichengloss|cortex}}) composed of densely packed fungal threads (hyphae) standing perpendicular to the surface; in ''O.&nbsp;kerguelensis'' the cortex may exceed 1&nbsp;mm in the centre.<ref name="Poulsen et al. 2001"/>

Green algal partners (a ''Coccomyxa''-like {{lichengloss|photobiont}}) occupy a layer beneath the cortex, but conspicuous vertical columns of algal cells periodically pierce the cortex almost to the surface. This three-dimensional arrangement helps the symbiosis photosynthesise through the massive wall. The inner body (medulla) is thin and often blends with grains of the underlying basalt or granite. No secondary metabolites have been detected by thin-layer chromatography.<ref name="Poulsen et al. 2001"/>

Reproduction is by plentiful urn-shaped ({{lichengloss|urceolate}}) apothecia deeply embedded in the thallus. Each fruiting cup contains asci that lack the dome-like amyloid cushions seen in many relatives; nevertheless the ascus wall stains pale blue in iodine, indicating a weakened amyloid reaction. Eight colourless, single-celled spores (ascospores) measuring roughly 22–29 × 16–19&nbsp;μm are produced. Immersed pycnidia yield long, curved asexual spores (conidia) about 15–25&nbsp;μm in length.<ref name="Poulsen et al. 2001"/>

==Habitat and distribution==

As a genus ''Orceolina'' is confined to the wind-lashed subantarctic islands of the southern Indian Ocean. Both species colonise exposed, vegetation-free basaltic or granitic rocks and pebbles from near sea level to the higher alpine ridges (up to roughly 650&nbsp;m). Confirmed records come from the Kerguelen Islands, Crozet Islands, Marion and Prince Edward Islands, and Heard Island. ''O.&nbsp;kerguelensis'' tends to be more common on drier, west-facing slopes, whereas ''O.&nbsp;antarctica'' often occupies slightly moister ridges, but the two can co-occur. No populations are known outside this isolated subantarctic archipelago belt, making ''Orceolina'' an example of high-latitude island endemism.<ref name="Poulsen et al. 2001"/>

==Species==

* ''Orceolina antarctica'' {{au|(Müll.Arg.) R.S.Poulsen & Søchting 2001)}} * ''Orceolina kerguelensis'' {{au|(Tuck.) Hertel 1970)}}

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

<ref name="CoL_CDS8Z">{{Catalogue of Life |id=CDS8Z |title=''Orceolina'' |access-date=9 July 2025}}</ref>

<ref name="Ertz et al. 2017">{{cite journal |last1=Ertz |first1=Damien |last2=SøChting |first2=Ulrik |last3=Gadea |first3=Alice |last4=Charrier |first4=Maryvonne |last5=Poulsen |first5=Roar S. |title=''Ducatina umbilicata'' gen. et sp. nov., a remarkable Trapeliaceae from the subantarctic islands in the Indian Ocean |journal=The Lichenologist |volume=49 |issue=2 |year=2017 |doi=10.1017/S0024282916000700 |pages=127–140 |bibcode=2017ThLic..49..127E }}</ref>

<ref name="Poulsen et al. 2001">{{cite journal |last1=Poulsen |first1=R.S. |last2=Schmitt |first2=I. |last3=Søchting |first3=U. |last4=Lumbsch |first4=H.T. |title=Molecular and morphological studies on the subantarctic genus ''Orceolina'' (Agyriaceae) |journal=The Lichenologist |volume=33 |issue=4 |year=2001 |doi=10.1006/lich.2001.0327 |pages=323–329 |bibcode=2001ThLic..33..323P }}</ref>

<ref name="Species Fungorum synonymy">{{cite web |title=Synonymy. Current Name: ''Orceolina'' Hertel, Vortr. GesGeb. Bot., ser. 2 4: 182 (1970) |url=https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=3633 |publisher=Species Fungorum |access-date=9 July 2025}}</ref>

<ref name="Tuckerman 1875">{{cite journal |last=Tuckerman |first=E. |year=1875 |title=Lichens of Kerguelen's Land |journal=Bulletin of the Torrey Botanical Club |volume=6 |pages=57–59 |doi=10.2307/2477595 |jstor=2477595 |url=https://www.biodiversitylibrary.org/page/646689}}</ref>

<ref name="Wijayawardene et al. 2020">{{cite journal |display-authors=6 |last1=Wijayawardene |first1=Nalin |last2=Hyde |first2=Kevin |first3=LKT |last3=Al-Ani |first4=S |last4=Dolatabadi |last5=Stadler |first5=Marc |last6=Haelewaters |first6=Danny |last7=Tsurykau |first7=Andrei |last8=Mesic |first8=Armin |last9=Navathe |first9=Sudhir |last10=Papp |first10=Viktor |last11=Oliveira Fiuza |first11=Patrícia |last12=Vázquez |first12=Víctor |last13=Gautam |first13=Ajay |last14=Becerra |first14=Alejandra G. |last15=Ekanayaka |first15=Anusha |last16=K. C. |first16=Rajeshkumar |last17=Bezerra |first17=Jadson |last18=Matočec |first18=Neven |last19=Maharachchikumbura |first19=Sajeewa |last20=Suetrong |first20=Satinee |year=2020 |title=Outline of Fungi and fungus-like taxa |journal=Mycosphere |volume=11 |pages=1060–1456 |doi=10.5943/mycosphere/11/1/8 |doi-access=free|hdl=10481/61998 |hdl-access=free }}</ref>

}}

{{Taxonbar|from=Q7100165}}

Category:Baeomycetales Category:Lichen genera Category:Baeomycetales genera Category:Taxa described in 1970 Category:Taxa named by Hannes Hertel