DNA metabarcode analysis
A total of 2, 231, 208 and 2, 796, 381 pair-end reads were obtained after the quality control test for ITS and 16S markers, respectively. Rarefaction curves for both genetic markers (Supplementary Figure 1) showed that our sampling was sufficient to cover species diversity present in the guts and galleries of I. typographus . A count of assigned ASVs in respect to season and sample type is summered in Table 1. The reads were grouped into 201 fungal and 239 bacterial ASVs in the spring season and 226 fungal and 560 bacterial ASVs in the summer season. The total number of assigned ASVs in the summer season is increased compared to spring due to the additional sampling of phloem samples.