Fuscidea ramboldioides

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Fuscidea ramboldioides is a rock-dwelling crusty lichen in the Fuscideaceae family. It was first described from Mount Freycinet in eastern Tasmania in 2001, based on specimens collected in 1999. Since then, it has also been found on the Australian mainland, including New South Wales and Western Australia.

What it looks like
- It forms pale to greyish-brown crusts on granite rocks, sometimes spreading nearly a metre across.
- The surface is cracked into small, tile-like patches (rimose-areolate) and feels rough and somewhat scaly.
- The thallus is about 120–150 micrometers thick. The photosynthetic partner is a green alga with cell sizes around 10–16 micrometers.
- Apothecia (the fruiting bodies) are scattered on the crust, black discs with a thick margin. They are usually 0.2–0.5 mm wide and sit directly on the crust.

How it grows and reproduces
- The inside of the lichen includes eight-spored asci and large, brown, oblong-elliptical ascospores, typically 9–15 by 4–8 micrometers. In young lichens the spores are clear, but at maturity they become brown with a single septum.
- Asexual structures are rare; tiny, inconspicuous pycnidia may occur, producing small ellipsoid conidia.

Chemistry and identification
- The medulla tests negative (no color change with common chemical tests).
- Under ultraviolet light, the lichen glows faint white due to the presence of the compound divaricatic acid.
- F. ramboldioides is most reliably distinguished from similar look-alikes by its large, brown, single-septate ascospores and its divaricatic acid chemistry.

Telling it apart from Ramboldia petraeoides
- Ramboldia petraeoides is a common Tasmanian rock lichen that looks similar but has a darker, less cracked (less scurfy) thallus and a glossy, flat, dark-brown apothecium.
- Chemically, Ramboldia petraeoides contains norstictic acid and has narrowly ellipsoid, simple (not 1-septate) spores, whereas F. ramboldioides has large, 1-septate spores and contains divaricatic acid.

Habitat and distribution
- F. ramboldioides is a crust on Devonian granite, growing on exposed rock faces or moist overhangs.
- It was first found at the summit of Mt Freycinet on the east coast of Tasmania, where it is very common, but at lower elevations it occurs less and in associated, drier lichen communities.
- Mainland records from New South Wales and Western Australia show that the species can exist in drier inland settings, with a generally darker, thinner thallus and thinner apothecia than the Tasmanian populations.

In short, Fuscidea ramboldioides is a widespread rock-dwelling lichen of granite that forms broad, greyish crusts and is best recognized by its large, brown, single-septate spores and divaricatic acid chemistry, helping distinguish it from similar species.