''Xanthoparmelia scabrosa'', jocularly known as sexy footpath lichen or sexy pavement lichen, is a

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 tolerates a very wide range of substrata, predominantly rock but also tree bark, roofing tiles, glass, and in wetter areas bitumen paths and roads.

Taxonomy and naming

The lichen was first formally described under the name ''Parmelia scabrosa'' in 1847 by botanist Thomas Taylor. The type was collected by botanist James Drummond near Swan River in Western Australia. It became known as a species of ''

Xanthoparmelia ''Xanthoparmelia'' (commonly known as green rock shields or rock-shield lichens) is a genus of foliose lichen in the family Parmeliaceae.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, ''Xanthoparmelia'' is syn ...

'' in 1974 when

Mason Hale Mason Ellsworth Hale, Jr. (September 23, 1929 – April 23, 1990) was one of the most prolific lichenologists of the 20th century. Many of his scholarly articles focused on the taxonomy of the family Parmeliaceae. Hale was one of the first liche ...

promoted that

subgenus In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between t ...

of ''

Parmelia Parmelia may refer to: * Parmelia (barque), the vessel that in 1829 transported the first settlers of the British colony of Western Australia * ''Parmelia'' (fungus), a genus of lichens with global distribution * Parmelia, Western Australia Pa ...

'' to generic status. The lichen was dubbed 'sexy footpath lichen' in a talk for the Auckland Botanical Society by Allison Knight. The name was popularised by Peter de Lange as 'sexy pavement lichen'.

Description

''Xanthoparmelia scabrosa'' has a

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 ...

that is foliose (leafy in appearance). The upper surface is yellow-green, while the lower surface is pale to dark brown.

Habitat and range

''Xanthoparmelia scabrosa'' is common in Australia and New Zealand, also occurring on

Norfolk Island Norfolk Island (, ; Norfuk: ''Norf'k Ailen'') is an external territory of Australia located in the Pacific Ocean between New Zealand and New Caledonia, directly east of Australia's Evans Head and about from Lord Howe Island. Together with ...

, Papua New Guinea, Fiji, Argentina, South Africa and Japan. In New Zealand it grows abundantly on roads and footpaths, ordinarily an inhospitable environment for lichens.

Chemistry

''Xanthoparmelia scabrosa'' appears to tolerate the high levels of

heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as ...

present in asphalt by accumulating these in the

. It can also accumulate high levels of calcium. These abilities may make it useful for

phytoremediation Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomi ...

Medical use

''Xanthoparmelia scabrosa'' has been marketed as a treatment for

erectile dysfunction Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...

, but many scientists do not recommend this use. While the lichen contains a

PDE5 inhibitor A phosphodiesterase type 5 inhibitor (PDE5 inhibitor) is a vasodilating drug that works by blocking the degradative action of cGMP-specific phosphodiesterase type 5 (PDE5) on cyclic GMP in the smooth muscle cells lining the blood vessels supplyi ...

, which may inhibit an enzyme responsible for

impotence Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...

, the same substance may itself be toxic. The lichen is also high in toxic heavy metals.

References