The genus Hygrocybe subgenus Hygrocybe in the Dominican Republic: phylogeny, diversity, and description of seven novel species and one variety (Agaricomycetes, Hygrocybaceae)

The genus Hygrocybe (Hygrocybaceae) exhibits remarkable diversity in the tropical forests of the Dominican Republic, particularly within H. subgenus Hygrocybe. Following over 20 years of fieldwork (2006–2026), seven new taxa are described herein based on morphological, molecular, and ecological analyses. Phylogenetic reconstructions using nuclear ribosomal ITS and LSU sequences resolved four well-supported clades in H. subgenus Hygrocybe (/ appalachianensis, / acutoconica, / conica, and / hypohaemacta), each corresponding to a distinct evolutionary lineage.

The novel species include H. citrinonigrescens, distinguished by its lemon-yellow pileus, which blackens with age, and the presence of dimorphic basidia in some basidiomata; H. jarabacoensis, a fibrillose, greenish-yellow species associated with coniferous forests; H. perdomoi, a species from the Dominican Republic and Florida that features small, completely viscid, yellow-orange to scarlet-red basidiomata and shares morphological similarities with H. acutoconica; H. pseudohypohaemacta and H. variecolor, two phylogenetically close yet morphologically divergent taxa within H. section Velosae; and H. xerophila, a species described from Florida, USA, and the Dominican Republic.

Molecular data also revealed cryptic diversity, such as H. parabolica, which is notable for its bisporic basidia and affinity for burned habitats. Dimorphic basidia and spores are reported for the first time in three species of H. subgenus Hygrocybe section Hygrocybe, viz., H. citrinonigrescens, H. parabolica, and H. xerophila. The study highlights the significance of the Dominican Republic as a hub of Hygrocybe diversity, with species exhibiting specialized adaptations to tropical ecosystems, including associations with disturbed or serpentine soils.

These findings expand the understanding of Neotropical fungal biodiversity and emphasize the conservation value of Caribbean forests.