Filamentous fungal communities associated with the eastern larch beetle ( <i>Dendroctonus simplex</i> LeConte) in Minnesota, including new Ophiostomatales species

The eastern larch beetle (<i>Dendroctonus simplex</i> LeConte) is a native and historically nonaggressive inhabitant of <i>Larix laricina</i> trees in North America. Since 2001, however, <i>D. simplex</i> has experienced an uncharacteristic and prolonged outbreak that has impacted trees on approximately 90% of the <i>L. laricina</i> forests in Minnesota. To investigate the fungal communities within <i>D. simplex</i> galleries during this outbreak, we isolated fungi from 56 <i>D. simplex</i>-infested trees across seven sites in Minnesota. We recovered 45 fungal species, including four new species in the order Ophiostomatales, proposed as <i>Graphilbum insulare</i>, sp. nov., <i>Ophiostoma itasca</i>, sp. nov., <i>Ophiostoma minnesotense</i>, sp. nov., and <i>Ophiostoma pseudoips</i>, sp. nov. Additionally, based on phylogenetics and morphological traits, we recommend a new taxonomic classification for <i>Leptographium simplex</i>, comb. nov. previously described as <i>Graphium simplex</i> from <i>D. simplex</i> galleries in Vermont, USA. At the community level, most isolates were in the phylum Ascomycota (82% of the total relative abundance), followed by Basidiomycota (12%). The most frequently isolated orders were Ophiostomatales (59% of the total relative abundance), Hypocreales (9%), and Pleosporales (8%). One species, <i>Grosmannia americana</i>, accounted for more than half of all isolates recovered. These results improve our understanding of the fungi associated with a bark beetle outbreak and an understudied tree species.