Abstract:
Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are small wood-boring insects that live in
an obligate symbiosis with fungi, which serve as their primary food source. Beetles residing in the
genus Euwallacea have evolved a unique association with a clade of Fusarium that falls within the
aptly named Ambrosia Fusarium Clade (AFC). The discovery of the invasive polyphagous shot hole
borer, E. fornicatus, in South Africa, has heightened awareness of ambrosia beetles and their
symbionts in the country. In this study, we investigated the Fusarium symbionts of three species
of Euwallacea in South Africa, with a specific focus on those associated with E. xanthopus. Isolations
of Fusarium strains from both living and dissected beetles yielded nearly 100 isolates. Using
multigene phylogenetic analyses, these isolates were identified as six different Fusarium species.
Fusarium hypothenemi and F. euwallaceae have previously been reported from South Africa.
Fusarium pseudensiforme and Fusarium AF-6 are new records for the country. The remaining two
species are new to science and are described here as F. rufum sp. nov. and F. floriferum sp. nov.
Targeted fungal isolation from specific beetle body parts revealed that the AFC species collected
were typically associated with the dissected beetle heads and helped us identify the likely
nutritional symbiont of E. xanthopus. This study highlights the understudied diversity of fungal
associates of ambrosia beetles present in South Africa.
