Placopsis rhodocarpa
Placopsis rhodocarpa is a species of lichen-forming fungus in the family Trapeliaceae. It forms radiating, rosette-like crusts on rock and clayey soil, coloured dark green to pale greenish or whitish, and produces small granular soredia as well as flat, pinkish cyanobacteria-containing structures. When fertile, the lichen bears fruiting bodies with rose-pink to red-brown and conspicuously thickened rims. The species has a Southern Hemisphere distribution, recorded from Ecuador and Bolivia southward into Chile, and also from Australia and New Zealand.
Taxonomy
Placopsis rhodocarpa was introduced by William Nylander in 1861, when he described it as Squamaria rhodocarpa from alpine rock in the Andes. In the original description he characterised the species as a pale, firmly attached crust that becomes uneven and slightly warted towards the centre but breaks into radiating fissures at the margin, with scattered flesh-coloured cephalodia and medium-sized, red to brick-red apothecia edged by an intact. He also recorded oblong to broadly ellipsoid ascospores and an iodine-induced blue staining reaction of the hymenium.Major nomenclatural databases do not agree on the author citation for the current name. Nylander described the species in 1861 as Squamaria rhodocarpa and, in the same paper, introduced the name Placopsis and referred to the species as Placopsis rhodocarpa. Subsequently, some modern treatments cite the name as Placopsis rhodocarpa. Index Fungorum and Species Fungorum instead cite the transfer to Placopsis from a later source and attribute the combination to Lindsay as Placopsis rhodocarpa. Wetmore later published the same combination in 1963, but this is treated as an isonym rather than a separate name.