Morphology and multilocus phylogeny illuminate novel taxa in Capnodiaceae (Ascomycota, Dothideomycetes, Capnodiales)

Capnodiaceae is a major family of sooty mold fungi, but its species diversity, host associations, and geographic distribution remain insufficiently documented in China. Many taxa in this family have been described based on limited morphological information or incomplete molecular datasets, resulting in unresolved generic and species boundaries. In this study, newly collected Capnodiaceae material from China was examined using morphological observations, culture characteristics, host and geographic information, and four-locus phylogenetic analyses based on ITS, LSU, tef 1-α, and rpb 2 sequence data.

A total of 37 newly collected strains associated with 25 host plant taxa belonging to 23 genera and 19 families were included. Phylogenetic analyses resolved several well-supported lineages within Capnodiaceae and supported the recognition of one new genus, Hyphopolychaeton, and eight new species in Conidiocarpus, Leptoxyphium, Polychaeton, and Hyphopolychaeton. In addition, 11 new host records and three new records for China are documented.

Host and geographic information showed that several taxa, including Conidiocarpus cinnamomi and C. caucasicus, occur on multiple host plants, indicating that host association alone should not be used as a primary criterion for species delimitation. Morphological comparisons showed that the position and structure of the conidiogenous region within the conidioma are informative for generic delimitation when congruent with multilocus phylogenetic evidence.

In contrast, minor quantitative differences in conidiomatal or conidial dimensions may represent intraspecific variation when not supported by clear molecular divergence. An expanded Leptoxyphium phylogeny including all available unnamed strains further supports a conservative interpretation of species boundaries in this genus. Overall, this study provides new morphological, ecological, host-associated, geographic, and multilocus molecular data for Chinese Capnodiaceae and strengthens the reference framework for species recognition and generic delimitation in sooty mold fungi.