Panaeolus oligotrophus: A new species from central Florida, with notes on Panaeolus pumilus and Crucispora rhombisperma

Panaeolus oligotrophus sp. nov., a species macromorphologically resembling Panaeolus cinctulus, was collected in central Florida. Its macro- and micromorphological features are described and compared with all other known Panaeolus species. Color photos of the fruiting bodies and micrographs of key microscopic features are provided, along with an updated phylogenetic analysis. A microscopic reexamination of the holotype of Panaeolus pumilus supports its synonymy with P. cinctulus. The potential for psilocybin production by P. oligotrophus was determined by the characterization of the psilocybin gene cluster through whole genome sequencing. Phylogenetic and morphological evidence also supports the placement of Crucispora rhombisperma within Panaeolus, for which the new combination Panaeolus rhombispermus is proposed. This paper makes two interesting additions to the genus Panaeolus: P. rhombispermus introduces the novelty of an extremely differentiated spore morphology, and Panaeolus oligotrophus provides a rare example of Panaeolus in the underexplored niche of oligonutritive sandy soil.