Unveiling cryptic diversity of Diaporthe associated with leaf spots of Fagaceae in China using an integrative taxonomic approach

The genus Diaporthe comprises a functionally diverse group of fungi, inhabiting plant tissues as pathogens, endophytes, and saprobes. Many species cause significant diseases in economically and ecologically important woody plants. Despite extensive research on the taxonomy and phylogeny of Diaporthe over the past two decades, species delineation remains challenging due to the high morphological plasticity among the more than 1,000 described taxa. In practice, molecular phylogenetic divergence has become the primary criterion for species delimitation, as morphological characters often fail to resolve species boundaries. In this study, we employed an integrative taxonomic approach combining multi-locus phylogeny with morphological characterization to investigate Diaporthe isolates associated with leaf spot diseases on Fagaceae , a dominant tree family in Chinese forests. Our investigation resolved eight distinct lineages, including five novel species described herein: namely D. castanopsidicola , D. changjiangensis , D. cyclobalanopsidicola , D. liangxii , and D. lithocarpicola from Guangdong and Hainan Provinces, China. These findings significantly contribute to resolving the cryptic diversity of Diaporthe and expand our understanding of the fungal communities driving foliar diseases in Fagaceae .