''Punctelia reddenda'' is a widely distributed species of

foliose lichen Foliose lichen is one of the morphological classes of lichens, which are complex organisms that arise from the symbiotic relationship between fungi and a photosynthetic partner, typically algae. This partnership allows lichen to live in diverse ...

in the family

Parmeliaceae The Parmeliaceae is a large and diverse family of Lecanoromycetes. With over 2700 species in 71 genera, it is the largest family of lichen-forming fungi. The most speciose genera in the family are the well-known groups: '' Xanthoparmelia'' ( 822 ...

. It occurs in Africa, Europe, North America, and South America, where it grows on bark and on rock.

Taxonomy

It was first described scientifically in 1903 by Scottish cryptogam specialist

James Stirton James Stirton (1833, Coupar Angus, Perthshire – 14 January 1917, Glasgow) was a Scottish physician and one of Scotland's leading experts on cryptogamic botany. His investigations in bryology and lichenology earned him a world-wide reputation. B ...

, as ''Parmelia reddenda''. The type was collected by botanist James McAndrew near New Galloway in Scotland. In 1982, Hildur Krog transferred the

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

to ''

Punctelia ''Punctelia'' is a genus of foliose lichens belonging to the large family Parmeliaceae. The genus, which contains about 50 species, was segregated from genus ''Parmelia'' in 1982. Characteristics that define ''Punctelia'' include the presence of ...

'', a newly

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

genus, with 22

pseudocyphella Pseudocyphellae (singular ''pseudocyphella'') are structures in lichens that appear as tiny pores on the outer surface (the cortex of the lichen. They are caused when there is a break in the cortex of the lichen, and the medullary hyphae extend t ...

-possessing species segregated from '' Parmelia''.

Description

The lichen has an upper

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

surface that is grey, and covered with bright soredia. The lower surface of the thallus is black. The thallus diameter is typically broad, comprising irregularly branched and laterally overlapping lobes that are wide with rounded tips. Point-like, conspicuous (i.e., readily visible) pseudocyphellae are abundant on the surface. Also abundant are coarse, granular soredia. The medulla is white. The cortex is K+ (yellow), indicating the presence of atranorin, while the medulla is negative for all

lichen spot tests A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical on different parts of the lichen and noting the colour change (or lack thereof) associated with application of the chemical ...

. A chemical analysis of Brazilian specimens using thin layer chromatography revealed the known compounds praesorediosic acid, protopraesorediosic acid, and protolichesterinic acid as well as an unidentified

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

. The North American species '' Punctelia appalachensis'' is similar in appearance to ''P. reddenda'', with a black thallus undersurface and negative medullary spot test reactions. However, it is distinguishable from ''P. reddenda'' because rather than soredia, it has abundant laminal and marginal (growths of the upper cortex or thallus margin, usually with a constricted base, that fall away as

propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...

s).

Habitat and distribution

''Punctelia reddenda'' grows on bark, but has also been recorded growing on rock. An older (1974) source considered its European distribution to be more or less limited to coastal areas ranging from southern Sweden to

Brittany Brittany (; french: link=no, Bretagne ; br, Breizh, or ; Gallo language, Gallo: ''Bertaèyn'' ) is a peninsula, Historical region, historical country and cultural area in the west of modern France, covering the western part of what was known ...

. A 2008 survey of parmelioid lichens in Europe indicated its presence in Germany, Spain, France, Greece, Ireland, and

Madeira ) , anthem = ( en, "Anthem of the Autonomous Region of Madeira") , song_type = Regional anthem , image_map=EU-Portugal_with_Madeira_circled.svg , map_alt=Location of Madeira , map_caption=Location of Madeira , subdivision_type=Sovereign st ...

, also noting that it was extinct in Sweden. In North America, its centre of distribution is the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

. In the

Great Smoky Mountains National Park Great Smoky Mountains National Park is an American national park in the southeastern United States, with parts in North Carolina and Tennessee. The park straddles the ridgeline of the Great Smoky Mountains, part of the Blue Ridge Mountains, whi ...

, it is only found at elevations greater than , in

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ...

forests in the mountains. In South America, it occurs in Bolivia, Brazil, Chile, and Venezuela. It is also found in South Africa and Macaronesia.

References

{{Taxonbar, from=Q10671145 reddenda Lichen species Lichens described in 1878 Lichens of Africa Lichens of Europe Lichens of North America Lichens of South America Lichens of Macaronesia Taxa named by James Stirton