About Buellia spuria (Schaer.) Anzi
Buellia spuria, common name the disc lichen, is a white to light ashy gray crustose areolate lichen. It is epilithic, meaning it grows on rocks, and it typically inhabits montane habitats. It has a prominent, more or less continuous prothallus that forms a black edge; this prothallus is also visible as a hypothallus in the cracks between the lichen's areolas, creating a sharp contrast against the whitish or ashy colored areolas. This lichen prefers growing on mafic, siliceous rock substrates. In Joshua Tree National Park, it can be found growing on vertical granite and gneiss faces within washes. It is common across the Northern Hemisphere worldwide, and very common in the Sonoran Desert, ranging from southern California to Arizona in the United States, and to Baja California, Sonora, Chihuahua, and Sinaloa in Mexico. It looks similar to the related species Buellia stellulata, but differs from it in secondary chemistry. Additionally, Buellia spuria is common across the entire Sonoran Desert region, while Buellia stellulata is restricted to coastal regions.
