Mycobiont maintenance: Establishing the basis for symbiont identity, specificity, and diversity in the ambrosia symbiosis

The ambrosia symbiosis is a diverse association wherein beetles cultivate fungi as an obligate food source inside wood. The association has evolved at least 12 times within the beetles, by over 3,200 species, which engage in greatly disparate ecological habits. The association has at least 6 origins within the fungi and includes some important plant pathogens, but otherwise very little is known about the mycobionts, including their identity, specificity to beetles, and diversity of function. Fungal communities of beetles were observed here using high-throughput metabarcoding to establish the identity of primary symbionts. Analyses of symbiont specificity and diversity were used to gain support for hypotheses of symbiont maintenance and evolutionary theories. These results establish a basis for communicating about this hyper-diverse symbiosis and for testing hypotheses of symbiont origin and function. Additionally, symbiont community descriptions will inform government agencies about which beetles may carry fungi of phytosanitary concern or act as invasive species.