Fungal Communities Associated with Siricid Wood Wasps: Focus on <i>Sirex juvencus</i>, <i>Urocerus gigas</i>, and <i>Tremex fuscicornis</i>

We investigated the diversity and occurrence of wood wasps in Lithuania and determined communities of associated fungi. Trapping of wood wasps resulted in three different species, including <i>Sirex juvencus</i>, <i>Urocerus gigas</i>, and <i>Tremex fuscicornis</i>. Fungal culturing from adult females of <i>T. fuscicornis</i> mainly resulted in fungi from the genera <i>Penicillium</i> and <i>Trichoderma</i>. High-throughput sequencing of ITS2 rDNA resulted in 59,797 high-quality fungal sequences, representing 127 fungal OTUs. There were 93 fungal OTUs detected in <i>U. gigas</i>, 66 in <i>S. juvencus</i>, and 10 in <i>T. fuscicornis</i>. The most common fungi were <i>Fusarium sporotrichioides</i> (63.1% of all fungal sequences), <i>Amylostereum chailletii</i> (14.9%), <i>Penicillium crustosum</i> (7.8%), <i>Microascus</i> sp. 2261_4 (5.0%), and <i>Pithoascus ater</i> (2.1%). Among these, only <i>A. chailletii</i> was found in all three insect species with the highest relative abundance in <i>U. gigas</i> (15.2%), followed by <i>S. juvencus</i> (7.7%), and the lowest in <i>T. fuscicornis</i> (0.3%) (<i>p</i> < 0.0003). Correspondence analysis of fungal communities showed a distant placement of different species of wood wasps, indicating that fungal communities in each of these were largely different. In conclusion, the study showed that the economically important tree pathogen <i>A. chailletii</i> was among the most common fungal OTUs associated with siricid wood wasps.