''Usnea sphacelata'' is a species of saxicolous (rock-dwelling), fruticose lichen in the large 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 is found in both polar regions of Earth, as well as in southern and northern South America and in New Zealand.

Taxonomy

The lichen was formally described as a new species in 1823 by Scottish botanist Robert Brown. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was collected from Melville Island in the Canadian

Arctic Archipelago The Arctic Archipelago, also known as the Canadian Arctic Archipelago, is an archipelago lying to the north of the Canadian continental mainland, excluding Greenland (an autonomous territory of Denmark). Situated in the northern extremity of No ...

. A 2007 study using

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

and morphological analysis of a large number of Antarctic ''Usnea'' specimens suggests that ''Usnea sphacelata'' comprises at least two genetically distinct groups with no clear differences in morphology.

Description

''Usnea sphacelata'' has a range of distinctive morphological characteristics. Its is relatively thin, accounting for about 20–40% of its structure.

Soralia Soredia are common reproductive structures of lichens. Lichens reproduce asexually by employing simple fragmentation and production of soredia and isidia. Soredia are powdery propagules composed of fungal hyphae wrapped around cyanobacteria o ...

, which are numerous, are typically restricted to the ultimate . Minute , which are often pigmented, can be observed on its surface. are usually absent from this species. Additionally, its pigmentation is noteworthy; the upper portion is conspicuously

variegated Variegation is the appearance of differently coloured zones in the leaves and sometimes the stems and fruit of plants. Species with variegated individuals are sometimes found in the understory of tropical rainforests, and this habitat is the s ...

, or it can be continuously pigmented towards the tips. This set of features helps to distinguish ''Usnea sphacelata'' from other

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

Antarctic ''

Usnea ''Usnea'' is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, The genus is in the f ...

'' species, including '' U. antarctica'', '' U. aurantiaco-atra'', '' U. subantarctica'', and '' U. trachycarpa''.

Distribution and habitat

The lichen has a bipolar distribution; that is, it occurs in both the Antarctic and the Arctic. It is also found in southern South America, the northern Andean regions of South America, and the

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

of New Zealand. In the

Windmill Islands The Windmill Islands are an Antarctic group of rocky islands and rocks about wide, paralleling the coast of Wilkes Land for immediately north of Vanderford Glacier along the east side of Vincennes Bay. Kirkby Shoal is a small shoal area with de ...

area of continental Antarctica, ''Usnea sphacelata'' tends to grow in drier sun-exposed areas where snow does not tend to persist. Typical lichen associates at this location include '' Buellia frigida'', '' Buellia soredians'', ''

Pseudephebe minuscula ''Pseudephebe minuscula'' is a species of fruticose lichen in the family Parmeliaceae. In North America, it is known colloquially as coarse rockwool. It has an antitropical distribution. Description The lichen has a dark brown to almost black ...

'', and ''

Umbilicaria decussata Rock tripe is the common name for various lichens of the genus ''Umbilicaria'' that grow on rocks. They are widely distributed, including on bare rock in Antarctica, and throughout northern parts of North America such as New England and the Rocky ...

''. In some regions, the crustose ''Buellia frigida'' is often the only species that can become established on smooth, ice-polished rock. Once its thallus is about 2 cm or more in diameter, ''

'' or ''Usnea sphacelata'' often start growing near the centre of the thallus.

References

{{Taxonbar, from=Q21303574 sphacelata Lichen species Lichens described in 1823 Lichens of the Antarctic Lichens of the Arctic Lichens of New Zealand Lichens of northern South America Lichens of southern South America Taxa named by Robert Brown (botanist, born 1773)