Ophiostomatoid fungi associated with Ips bark beetles in China

Ips bark beetles are a genus of borer pests spanning throughout the Northern Hemisphere, many of which are conifer-killers and extremely destructive to forests and plantations. Fungal symbionts, especially ophiostomatoid fungi, have contributed to the success of Ips bark beetles. Recently, climate change has a multiplier effect, accelerating the tree mortality caused by bark beetle and fungal symbionts. However, few ophiostomatoid fungi associated with Ips bark beetles have been reported in China. This study aimed to investigate the ophiostomatoid fungi associated with Ipsbark beetles from China and deduce the patterns of ophiostomatoid fungal assemblages on Ips. In this study, 14,512 strains of the ophiostomatoid fungi were isolated from 1,265 vigorous adult beetles and 826 fresh galleries belong to eleven Ips species infesting 16 coniferous trees (including pines, spruces and larches) from 48 sampling sites in nine provinces or autonomous regions located in northeast, northwest and southwest China. Based on morphological features and phylogenetic analysis, 71 taxa belonging to eight genera were accurately identified (Ceratocystiopsis, Graphilbum,Grosmannia, Leptographium, Masuyamyces and Ophiostomain Ophiostomatales; Endoconidiophora and Graphium in Microascales), of which 38 new species were described in this paper. By comparing patterns of fungal assemblages, we found that the fungi showed a tendency to genetically co-differentiate with their vectors, and speculated that the host tree reinforces the coarse species-specific association between ophiostomatoid fungi and Ips bark beetles. This work further demonstrated the high diversity of ophiostomatoid fungi associated with Ipsbark beetles, and provided insight into their symbiotic associations.