Re-evaluation of the taxonomy and diversity of Russula section Foetentinae (Russulales, Basidiomycota) in Korea

Russula section Foetentinae is a group of ectomycorrhizal symbiont fungi that are integral in maintaining biodiversity in diverse ecosystems. Identification and accurate classification of these fungi has proven challenging because of significant similarities in morphology, particularly among fruiting bodies. The objective of this study was to re-evaluate the diversity and taxonomy of Russula section Foetentinae in Korea using both phylogenetic analysis and morphological characteristics. A phylogenetic tree was constructed using internal transcribed spacer sequences and compared against key morphological characteristics. Our results reassigned several taxa and established important ecological relationships among closely related species. The phylogenetic analysis produced strong support for seven species, two of which were previously identified, one was a new record to Korea, and one was an undescribed species which we propose to name R. catillus sp. nov. Russula section Foetentinae separated into four clades when molecular and morphological data were combined. An important finding of the study was that several taxonomic assignments based on morphological characters were inconsistent with more reliable molecular data. This study highlights the need for a genetic database that can be easily accessed and used in conjunction with morphological data in order to better resolve the evolutionary history of this important fungal group.