Taxonomic and phylogenetic studies reveal three new species of the genus Geastrum in the Corollina section from Brazil

This study describes three new species of Geastrum — G. iguassuense, G. nodimyceliale, and G. unisaccatum — based on morphological and molecular data from specimens previously identified as G. saccatum in the herbarium collection of the Institute of Natural Sciences – UFRGS. Morphological characterization involved macroscopic and microscopic features, including optical microscopy and scanning electron microscopy. Molecular data were obtained from the ITS and LSU regions of nuclear ribosomal DNA. Phylogenetic relationships were inferred using Bayesian and maximum likelihood inference methods. The results support the inclusion of the three proposed new species in the Corollina section of the genus Geastrum, revealing them to be well-founded and distinct evolutionary lineages. These findings highlight the underestimated diversity of Geastrum in the Neotropics and the taxonomic relevance of integrating molecular and morphological data. With the addition of the three new species, the Corollina section now comprises seventeen recognized species. Detailed descriptions, comparisons with morphologically similar species, illustrations, and an updated identification key for the Corollina section are provided.