''Ramalina geniculatella'' is a species of saxicolous (rock-dwelling), fruticose lichen in the family Ramalinaceae. It is found in the remote tropical island of

Saint Helena Saint Helena () is a British overseas territory located in the South Atlantic Ocean. It is a remote volcanic tropical island west of the coast of south-western Africa, and east of Rio de Janeiro in South America. It is one of three constitu ...

, where it grows on boulders and cliffs. It was formally described as a new species in 2008 by Dutch lichenologist

André Aptroot André Aptroot (Heemskerk, 1961) is a Dutch mycologist and lichenologist. In 1993 he did his PhD at the University of Utrecht under the supervision of Robbert Gradstein (nl). His dissertation was titled "Systematic studies on pyrenocarpous li ...

. The type specimen was collected by the author from

Prosperous Bay Plain Prosperous Bay Plain is an area on the eastern coast of Saint Helena, a British island territory in the South Atlantic Ocean. It is the site of the new Saint Helena Airport, and is notable for its high invertebrate biodiversity. Geography Prosper ...

at an elevation of ; there, it was found growing on basalt. The initially shrub-like, fruticose thallus of the lichen later becomes , reaching lengths of up to , although typically it is smaller, about . The branches of the thallus are about 0.5–1.2 mm wide and about 0.2–0.5 mm thick; they are geniculate (sharply bent) below the apothecia. The species epithet refers to this characteristic feature. Although the branches are greenish-grey, they are covered with whitish

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 ...

e, which gives the thallus an overall whitish appearance. Thin-layer chromatography shows that the species contains

usnic acid Usnic acid is a naturally occurring dibenzofuran derivative found in several lichen species with the formula C18H16O7. It was first isolated by German scientist W. Knop in 1844 and first synthesized between 1933-1937 by Curd and Robertson. Usnic a ...

, and sometimes boninic acid and protocetraric acids. The photobiont partner is dispersed in irregular groups throughout the medulla.

References

External links

Pictures of Tropical Lichens
– Image of species geniculatella Lichen species Lichens described in 2008 Taxa named by André Aptroot Lichens of the middle Atlantic Ocean {{Lecanorales-stub