Abstract

The genus Calostoma is known for unusual morphological features among puffball fungi. One species, Calostoma insigne, is classified as endangered due to habitat loss. Several fruiting bodies of Calostoma were encountered during a fungi foray in West Kalimantan, Indonesia. Therefore, this study aimed to confirm the identification of the several fruiting bodies of Calostoma encountered in West Kalimantan, Indonesia, through morphological and molecular data. The fruiting bodies were described based on macro- and micro-morphological features. Molecular analysis and phylogenetic tree construction were performed using the ITS4/5 sequence. The combination of morphological and molecular data confirmed the collection as C. insigne. This species is characterized by its white to cream basidiomata, distinguishing it from other Calostoma species. C. insigne BO24643 grows solitarily to gregariously near Dipterocarpaceae trees. It has beige to pale brown ostiolum, a smooth yellowish-brown to ochraceous exoperidium, and a smooth endoperidium that is concolorous with the exoperidium. Additionally, this species produces coarse spinulose spores. The BLAST comparison showed that C. insigne BO24643 specimen was closely related to C. insigne, with top hits (99–100%) from specimens in Thailand and the USA. The phylogenetic tree inferred from the ITS sequence placed BO24643 in the same clade as C. insigne with 100% bootstrap support. Locally, people sometimes consume fruiting bodies as sweet porridge. This study provides recent data on C. insigne in Indonesia and may contribute to the IUCN assessment of this species.