Sexual reproduction and saprotrophic dominance by the ambrosial fungus Flavodon subulatus (= Flavodon ambrosius)

Abstract

Abstract Ambrosia beetles farm symbiotic ambrosia fungi in wood. Ambrosia fungi generally belong to Ascomycota, rely upon beetles for dispersal, reproduce asexually, are poor saprotrophic competitors in wood, and lack fruit bodies. We provide the first account of consistent fruit body production in the absence of beetles by an ambrosia fungus, Flavodon ambrosius, the basidiomycete symbiont of Ambrosiodmus minor, a beetle native to Asia and introduced in North America. We collected resupinate fruit bodies in Florida and Taiwan with ITS rDNA that matches F. ambrosius. Taxonomic work indicates that these fruit bodies match the earlier synonym Flavodon subulatus from Asia. An inoculation experiment confirmed that the beetle-associated F. subulatus produces fruit bodies, indicating that it may be capable of beetle-free dispersal. High-throughput sequencing of experimental logs suggests that F. subulatus is a strong competitor and excludes native saprotrophic fungi. These results reveal the unique ecology and reproductive biology of Flavodon ambrosia fungi.