Pyrenula hibernica

Pyrenula hibernica is a crustose lichen, growing tight to the bark which it lives on and causing it to split as the tree grows.{{cite web |title=Temperate rainforest |url=https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/habitats/temperate-rainforest/ |website=Woodland Trust |access-date=27 November 2024}} The thallus of the lichen varies in colour from olive green to yellow-buff; it does not react to the C, K, KC or PD spot tests, but does react to UV exposure, turning pale yellow.{{cite web |title=Pyrenula hibernica - Descriptions|url=https://fungi.myspecies.info/taxonomy/term/8666/descriptions |website=Fungi of Great Britain and Ireland |access-date=27 November 2024}}

The lichen's perithecia are black, {{convert|1|-|1.2|mm}} in diameter, and situated {{convert|1|-|1.5|mm}} below the lichen's surface. In some specimens, only the ostiole is visible from the surface but sometimes may be clearly visible if the thallus is more translucent.

The species was originally described as Parmentaria chilensis, which had also been recorded in Colombia and Chile. However, in 2003, a paper by Javiar Etayo and André Aptroot proposed that this should be re-evaluated, with the European and Macaronesian specimens having the name Pyrenula hibernica. They found that the hibernica specimens were different from the type species since they have ascomata (fruiting bodies) which are almost always in groups of two to six with a shared ostiole and smaller ascospores, whereas the Pyrenula chilensis specimens had singular ascoma with their own ostioles and larger ascospores.{{cite journal |author1=Javiar Etayo |author2=André Aptroot |author2-link=André Aptroot |title=Pyrenula luteopruinosa sp. nov. from Panama and notes on other members of the genus |journal=Lichenologist |date=2003 |volume=35 |issue=3 |pages=233–236 |doi=10.1016/S0024-2829(03)00021-5|bibcode=2003ThLic..35..233E }}

Pyrenula hibernica grows on the smooth bark of Corylus (hazel), Ilex (holly), and Sorbus trees in sheltered, moist ravines, as well as more open slopes, especially in Ireland. The species is strongly associated with Atlantic hazelwood.{{cite web |author1=David Genney |title=The Scottish Beaver Trial: Lichen impact assessment 2010-2014, final report |url=https://www.nature.scot/sites/default/files/2017-07/Publication%202015%20-%20SNH%20Commissioned%20Report%20694%20-%20The%20Scottish%20Beaver%20Trial%20Lichen%20Impact%20Assessment%202010-2014%2C%20final%20report.pdf |website=Scottish Natural Heritage |access-date=27 November 2024 |date=2015}} It is restricted to temperate rainforest environments.{{cite web |title=The state of Scotland's rainforest |url=https://www.woodlandtrust.org.uk/media/4792/state-of-scotlands-rainforest.pdf |website=Woodland Trust |access-date=27 November 2024 |page=4 |date=April 2019}}

Pyrenula hibernica is a vulnerable species in the IUCN Red List categories, based on criteria D2 (having "a very restricted area of occupancy ... or number of locations").{{cite journal |author1=R.G. Woods |author2=B.J. Coppins |author2-link=Brian John Coppins |title=A Conservation Evaluation of British Lichens and Lichenicolous Fungi |journal=Species Status |date=2012 |volume=13 |url=https://data.jncc.gov.uk/data/39f3126a-5558-41e7-8b71-994c27a49541/SpeciesStatus-13-Lichen-LichenicolousFungi-WEB-2012.pdf |access-date=26 November 2024 |publisher=Joint Nature Conservation Committee |issn=1473-0154}}

In the United Kingdom, it is a protected species under Schedule 8 of the Wildlife and Countryside Act 1981, section 2(4) of the Nature Conservation (Scotland) Act 2004 and section 42 of the Natural Environment and Rural Communities Act 2006, as well as being designated a Nationally Rare species and a Biodiversity Action Plan priority.

Pyrenula hibernica is present at five sites in western Scotland including at Westerness, Loch Sunart and Mull.

The species was first discovered in Wales in 2005 by Neil Sanderson in the Ceunant Llennyrch National Nature Reserve. It was recorded on 14 undisturbed hazel bushes within the Ceunant Llennyrch gorge. It was initially recorded as sterile Pyrenula macrospora because all the characteristic perithecia 'fruit' were fully immersed in the thalli and not visible from the surface; this was corrected after a sample was taken, revealing the fruit. The perithecia are often not visible from the surface in Welsh specimens. In 2016, the lichen was reported on 23 hazel bushes at Ceunant Llennyrch which, {{as of|November 2022|lc=y}}, is the only population in Wales.{{cite web |author1=Sam Bosanquet |title=A review of non-vascular plant and fungal SSSI features in Wales - Lichens |url=https://naturalresources.wales/media/695442/nrw-evidence-report-369-a-review-of-non-vascular-plant-and-fungal-sssi-features-in-wales-lichens-accessible.pdf |website=Natural Resources Wales |access-date=26 November 2024 |pages=69–70 |date=September 2022}}

The species has been recorded in hazel woods in Borrowdale, Cumbria.

In 2016, Pyrenula hibernica was recorded in Madagascar, marking the species' first recorded specimen from Africa.

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Category:Pyrenula

Category:Lichen species

Category:Lichens described in 2003

Category:Lichens of Northern Europe

Category:Lichens of Madagascar

Category:Taxa named by André Aptroot