| Punctelia borreri | |
|---|---|
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Lecanorales |
| Family: | Parmeliaceae |
| Genus: | Punctelia |
| Species: | P. borreri
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| Binomial name | |
| Punctelia borreri | |
| Synonyms[1] | |
Punctelia borreri is a species of foliose lichen in the family Parmeliaceae. It is a common and widely distributed species, occurring in tropical, subtropical, and temperate regions of Africa, Asia, Europe, North America, Oceania, and South America. The lichen typically grows on bark of deciduous trees, and less commonly on rock. Some European countries have reported increases in the geographic range or regional frequency of the lichen in recent decades, attributed alternatively to a reduction of atmospheric sulphur dioxide levels or an increase in temperatures resulting from climate change.
The lichen is characterised by a greenish-grey to bluish-grey upper thallus surface, a black lower surface, pseudocyphellae on the surface of the thallus (tiny pores that facilitate gas exchange), and chemically, by the presence of gyrophoric acid in the medulla. There are several lookalike Punctelia species, including P. subrudecta, P. perreticulata, and P. reddenda. These can be distinguished from P. borreri by differences in chemistry, in the nature of the vegetative reproductive structures present on the thallus, or the colour of the thallus underside.
Punctelia borreri is named after William Borrer, a botanist who made the first scientific collections of the lichen in early 19th-century England. James Edward Smith was the first to publish a scientific description of the species in 1807, followed independently a year later by Dawson Turner. It was later assigned as the type species of Punctelia by Hildur Krog when she circumscribed the new genus in 1982. Punctelia borreri is used as a component of traditional Chinese medicine. The lichen has been shown to harbour other organisms, including endophytic fungi and lichenicolous fungi.