Novel Fusarium mutualists of two Euwallacea species infesting Acacia crassicarpa in Indonesia

Several species in the <i>Euwallacea fornicatus</i> complex have emerged as important pests of woody plants globally, particularly in habitats where they are invasive aliens. These beetles live in obligate symbioses with fungi in the genus <i>Fusarium</i>. In this study, we identified <i>Euwallacea</i> spp. and their fungal mutualists that have emerged as pests of planted <i>Acacia crassicarpa</i> in Riau, Indonesia. Morphological identification and phylogenetic analyses of the mitochondrial cytochrome oxidase <i>c</i> subunit I (<i>COI</i>) gene confirmed that <i>E. similis</i> and <i>E. perbrevis</i> are the most abundant beetles infesting these trees. Multilocus phylogenetic analyses of their fungal mutualists revealed their nonspecific association with six <i>Fusarium</i> species. These included <i>F. rekanum</i> and five novel <i>Fusarium</i> mutualists within the <i>Fusarium solani</i> species complex (FSSC), four of which reside in the Ambrosia <i>Fusarium</i> Clade (AFC). These new species are described here as <i>F. akasia, F. awan, F. mekan, F. variasi</i>, and <i>F. warna</i>.