Ophiostomatoid fungi associated with Ips bark beetles in China

Ips is a genus of bark beetles found throughout the Northern Hemisphere, many of which are highly destructive to coniferous forests and plantations. Fungal symbionts, especially ophiostomatoid fungi, have contributed to the success of Ips bark beetles. Recently, climate change accelerated tree mortality caused by bark beetles and their fungal symbionts. However, the knowledge of ophiostomatoid fungi associated with Ips bark beetles is inadequate in China. Therefore, this study investigated the ophiostomatoid fungal communities associated with different Ips bark beetles from various coniferous forest areas of China. A total of 14,512 ophiostomatoid fungal strains were isolated from 1265 vigorous adult beetles and 826 fresh galleries belonging to 11 Ips species infesting 16 coniferous tree species, including pines, spruces, and larches, from 42 sampling sites in nine provinces or autonomous regions in northeast, northwest and southwest China. Based on a combination of morphological features and phylogenetic analysis, 71 taxa belonging to eight genera were identified (Ceratocystiopsis, Graphilbum, Grosmannia, Leptographium, Masuyamyces, and Ophiostoma in Ophiostomatales; Endoconidiophora and Graphium in Microascales), of which 38 species were described as new. Comparing patterns of fungal assemblages indicated that fungal symbionts genetically co-differentiated with their vectors. Host trees possibly reinforce the coarse species-specific association between ophiostomatoid fungi and Ips bark beetles. This study further demonstrates the high diversity of ophiostomatoid fungi associated with Ips bark beetles and provides insights into their symbiotic associations.