Ophiostomatoid fungi associated with mites phoretic on bark beetles in Qinghai, China

Bark beetle galleries are complex ecosystems where many microbes and other arthropods co-exist with the beetles. Fungi isolated from these galleries are often referred to as ‘beetle associates’, but the nature of these associations are poorly understood. The possibility that many of these fungi might in fact be mite associates is often overlooked. Several recent studies explored the diversity of fungi from conifer-infesting bark beetles and their galleries in China, but only one study considered phoretic mites and their fungi from conifer-infesting bark beetles in Yunnan, southwestern China. We studied the mites and fungi from galleries of four spruce-infesting bark beetle species in the high altitude forests of Qinghai province, western China. Mites were identified based on morphological characteristics, and fungi based on DNA sequences of four gene regions. In total, 173 mite individuals were collected belonging to 18 species in 11 genera. A total of 135 fungal isolates were obtained from the mites, representing 14 taxa from the Ophiostomatales. The most frequently isolated fungus was Ophiostoma nitidum, which represented 23.5% of the total isolates. More fungal species were found from fewer mites and bark beetle species than from the study in Yunnan. Although we could not elucidate the exact nature of interactions between mites and their fungi, our results re-enforce that these organisms should not be ignored in pest risk assessments of bark beetles, that often focus only on the beetles and their fungi. Three new species are described: Grosmannia zekuensis, O. manchongi, and O. kunlunense spp. nov., and our data revealed that O. typographi, recently described from China, is a synonym of O. ainoae.Additional file 1: Fig. S1. Phylogram obtained from ML analyses of the partial BT and EF gene of Ophiostoma clavatum complex. Sequences obtained in this study are printed in bold type. ML and MP bootstrap support values (1000 replicates, normal type) above 75% are indicated at the nodes. Posterior probabilities (above 0.9) obtained from BI are indicated by bold lines at the relevant branching points. T = ex-type cultures. Scale bar = total nucleotide difference between taxa.Additional file 2: Fig. S2. Phylogram obtained from ML analyses of the partial BT and EF gene of Leptographium olivaceum complex. Sequences obtained in this study are printed in bold type. ML bootstrap support values (1000 replicates, normal type) above 75% are indicated at the nodes. Posterior probabilities (above 0.9) obtained from BI are indicated by bold lines at the relevant branching points. T = ex-type cultures. Scale bar = total nucleotide difference between taxa.Additional file 3: Table S1. Ophiostomatoid fungi reported from China.Additional file 4: Table S2. Numbers of mite individuals collected and numbers of mite individuals carring fungi in this study.Additional file 5: Table S3. Numbers of fungal isolates associated with mites from different beetle galleries. Shades of red indicate number of fungal isolates.Members of Tree Protection and Cooperation Programme (TPCP), the Department of Science and Technology (DST)-National Research Foundations (NRF), Center of Excellence in Tree Health Biotechnology (CTHB), and University of Pretoria, Pretoria, South Africa.http://www.imafungus.orgam2020BiochemistryGeneticsMicrobiology and Plant Patholog