The cetrarioid core group has been the focus of numerous taxonomic and phylogenetic studies in recent years, yet the phylogenetic resolution and support among these clades remains unclear. Here we use four commonly employed loci to estimate if their use increases phylogenetic resolution and support. The present study largely confirms the topologies of previous studies, but with increased support. Approximately half of the genera in the cetrarioid core were not monophyletic. Melanelia sorediella was clustered within Cetrariella, and the combination Cetrariella sorediella (Lettau) V. J. Rico & A. Thell comb. nov. is made. Additionally, the genus Flavocetrariella was supported as part of Nephromopsis and is considered to be a synonym of the latter. Finally, a comparison of genetic distances shows that the maximum intrageneric genetic distance encompassed by many cetrarioid genera is lower than that of many other genera in Parmeliaceae.

Nimisia deusta, based on Parmelia enteromorpha var. deusta, is shown to be the correct name for the species currently known as N. fuegiae. Original material collected by J. D. Hooker in 1842, and collections made by Henry Imshaug between 1968 and 1971, have shown that the species is more widely distributed than previously reported, being known throughout the southern tip of South America (Argentina: Isla Grande de Tierra del Fuego, Isla de los Estados; Chile: Cape Horn Islands; Falkland Islands), that it has a uniform secondary metabolite chemistry of fumarprotocetraric acid in the upper medulla (not lacking lichen substances as previously reported), and that it is not uniformly black but has a partly pale brown upper cortex.