Taxonomic revision of the genus Sarcosphaera (Ascomycota: Pezizales) in Europe and North America revealed unexpected diversity.

Sarcosphaera (Ascomycota: Pezizales) is a genus of rare spring fungi, currently encompassing a single species, S. coronaria, which is red-listed in many European countries. The genus is characterized by large bright-colored fruit-bodies and high arsenic content. This study investigates the genetic diversity across Europe and North America. Using integrated molecular techniques, including ITS and 28S rDNA sequencing, we aimed to resolve the taxonomic ambiguities and assess their arsenic hyperaccumulation capabilities, a rare trait among fungi. We identified the presence of two species in the Western Palearctic (S. coronaria, S. crassa) and at least 12 additional lineages in North America, indicating a more complex taxonomic structure than previously recognized. To consolidate the taxonomy and nomenclature of these fungi, we selected reference specimens for S. coronaria and S. crassa and discussed their morphological and ecological differences. Two genera, Caulocarpa (C. montana) and Hydnotryopsis (H. setchellii), a genus comprising hypogeous fungi, are newly placed in the genus Sarcosphaera. Sarcosphaera is thus another genus where the rapid evolution of hypogeous forms from their above-ground ancestors took place. Furthermore, two new Sarcosphaera species, S. columbiana and S. pacifica, are described from the Pacific Northwest. Investigation of arsenic content of Sarcosphaera species revealed that arsenic mass fractions in ascocarps vary significantly between species and even within species across different geographical locations. Our findings have important implications for the taxonomy and conservation of the S. coronaria species complex and also point to future directions for further research in the taxonomy, geomycology, and toxicology of this group of fungi.