Chrysothrix occidentalis

Chrysothrix occidentalis has a powdery, crust-like appearance that ranges in colour from bright yellow to yellow-green or yellow-orange. It does not have a protective outer layer (cortex and its structure is simple, adhering directly to its substrate. The lichen forms small, somewhat round colonies about 0.5–1 cm wide, which can merge over time to form larger irregular patches up to 10 cm wide. These colonies consist of tiny granular structures called soredia, which are fine and round in shape, measuring between 20–80 μm in width. The photosynthetic partner in this lichen, or photobiont, is a type of green algae, which is spherical and roughly 15–18 μm wide. The hyphae comprising the internal network of fungal threads are 1.6–3 μm thick. No supporting base layer, known as the hypothallus, is visible, and reproductive structures like apothecia and pycnidia have not been observed. Chemically, when tested, the lichen turns orange upon exposure to a solution of potassium hydroxide (K+). Its primary lichen products include leprapinic acid, with smaller amounts of calycin, vulpinic acid, and pulvinic dilactone.^[2]

Chrysothrix occidentalis is found in various places in the southwestern region of Western Australia. It typically grows on protected granite or laterite ledges within open Eucalyptus forests, ranging in altitudes between 100 and 650 m (330 and 2,130 ft). Some lichens species frequently found alongside Chrysothrix occidentalis include Buellia substellulans, Lecanora farinacea, Ramboldia petraeoides, Xanthoparmelia antleriformis, and X. tasmanica.^[2]