Stropharia misionensis and Stropharia viridis, two new species from native forests of Northern Argentina (Agaricomycetes, Agaricales)

Northern Argentina hosts tropical and subtropical forests with a rich but still underexplored diversity of Agaricales fungi. In this study, we describe two new species of Stropharia found growing on decaying wood in native forests: Stropharia viridis , from the Cedrela forest within Baritú National Park (Salta, Andean Yungas), and Stropharia misionensis , from the San Antonio Strict Natural Reserve (Misiones, Alto Paraná Atlantic Forests). Phylogenetic analysis based on the nuclear internal transcribed spacer (nrITS) region and the large subunit (nrLSU) of the nuclear ribosomal DNA placed both species in well-supported clades within Stropharia , thereby confirming their placement as distinct taxa within the genus. Stropharia viridis is characterized by a dull green to grayish yellow, viscid pileus, sinuate lamellae, and thick-walled inamyloid basidiospores; S. misionensis has a white pileus densely covered with brownish-red squamules, a membranous superior annulus, and subangular spores < 10 µm long. Both taxa present smooth and thick-walled, inamyloid basidiospores, and clamp connections in all tissues. Complete taxonomic descriptions, field photographs, drawings, photographs captured with the scanning electron microscope (SEM) of the basidiospores, and comparisons of similar and closely related species are provided. Additionally, UV fluorescence microscopy images reveal the presence of fluorescent cystidia in S. misionensis . Finally, since both species are restricted to decaying wood within native forests currently threatened by habitat loss, it is proposed that they should also be considered at risk.