Morphological and Phylogenetic Characterization of Four Additional <i>Xylaria</i> -associated Species: Three New Species and One Newly Recognized Species in Korea

The genus <i>Xylaria</i> Hill ex Schrank is an ecologically significant group of wood-decaying fungi that contribute to nutrient cycling and ecosystem stability in forests worldwide. Despite a recent global increase in the descriptions of new species, Korean <i>Xylaria</i> species have rarely been reexamined using modern taxonomic frameworks. In this study, dried specimens preserved at the Korea National Arboretum were re-identified through integrative morphological and molecular analyses using four genetic markers (ITS, ACT, TUB2, and RPB2). Consequently, one previously unrecorded species (<i>Xylaria frustulosa</i>) and three novel species (<i>Heteroxylaria aciculiformis</i>, <i>Xylaria gwangneungensis</i>, and <i>Xylaria pratimongolica</i>) were discovered. Morphological observations revealed that <i>H. aciculiformis</i> is characterized by its slender, needlelike, unbranched stromata with fine longitudinal striations and semi-exposed perithecia; <i>X. gwangneungensis</i> has distinctive capitate stromata with a short stipe and a solitary perithecium; and <i>X. pratimongolica</i> exhibits an erect, oriental brush-like stroma partially developed underground. Phylogenetic analyses supported the unique status of these taxa, as they formed distinct and well-supported clades separate from known species within <i>Xylariaceae</i>. These findings further elucidate the diversity of the <i>Xylariaceae</i> family and demonstrate the value of combining morphological and molecular data to resolve cryptic species within this genus.