Abstract
In this study, three novel fungal species belonging to the Nectriaceae family, Gliocladiopsis koreensis sp. nov., Ilyonectria koreensis sp. nov., and Mariannaea koreensis sp. nov., were discovered from soil samples collected at Iseung-ak Oreum on Jeju Island and the Upo Wetland in Changnyeong, Republic of Korea. They were confirmed as distinct species through molecular phylogenetic analyses using the ITS, TUB, Tef1, HIS3, and LSU sequences. Maximum-likelihood and Bayesian inference trees show that G. koreensis forms a sister clade with G. curvata, G. singaporiensis, and G. peggii, I. koreensis clusters closely with I. qitaiheensis and I. changbaiensis, and M. koreensis is phylogenetically related to M. atlantica, M. fusiformis, M. elegans var. punicea, and M. terricola. While all three new species exhibit unique morphological characteristics such as colony growth patterns, pigmentation, and microstructures that differentiate them from their closest relatives. The findings of these novel species contribute to the understanding of fungal diversity in these ecologically significant regions and highlight their potential applications in agriculture, nutrient cycling, and environmental restoration.