Fuscidea lightfootii and F. pusilla (Fuscideaceae, Umbilicariomycetidae, Ascomycota), two similar but genetically distinct species

The two corticolous species Fuscidea lightfootii (Sm.) Coppins & P. James and F. pusilla Tønsberg are morphologically and chemically similar and it has been suggested that they are conspecific. We investigated the interspecific relationship between F. lightfootii and F. pusilla using ITS, LSU and mtSSU rDNA. The combined multigene phylogeny shows that these species are genetically distinct. They are similar in ascocarp anatomy but in thallus morphology and substratum preferences there may be slight differences between them. Moreover, F. pusilla displays a broader ecological range than F. lightfootii. Even though some morphotypes appeared distinct and may be assigned to one of the two species with some degree of certainty, the use of DNA sequencing is recommended for their identification. Epitypes are designated for both species.