Genetics and Metabolism of Ambrosia Fungi
Symbiotic interactions between ambrosia beetles and ambrosia fungi are fascinating and there is a lot remaining to learn about them. Even the basic patterns in composition and dynamics of the symbiotic consortium are unclear. According to a traditional view, ambrosia beetles mechanically inoculate their galleries with clonal monocultures of a favored fungus species (Francke-Grosmann, 1967; Mueller et al., 2005). Alternative observations suggest that beetles may maintain a stable community of symbiotic fungi (Kuhnholz, 2004), or that the beetles can coexist with and develop on a number of interchangeable fungi recruited from the environment (Batra, 1966). This variety of views demonstrates how much data and experimentation is still needed to understand this spectrum of symbiosis.
We still don’t know whether it is the beetles which somehow choose the right fungus among the many opportunistic fungi in decaying wood, or if is the other way around, or both.
In one recent paper by our lab (Huang, 2019), we found that metabolic variation among five different groups of ambrosia fungi (with separate evolutionary origins of symbiosis with their respective beetles) was explained by their phylogenetic relationships to closely-related non-ambrosia fungi. The transitions into symbiosis did not appear to impact their carbon metabolism.
References
Huang, Y. (2019) Multiple evolutionary origins lead to diversity in the metabolic profiles of ambrosia fungi. Fungal Ecology, Vol. 38, pp. 80-88.
Batra, L.R. (1966) Ambrosia fungi: extent of specificity to ambrosia beetles. Science, 153, 193-195.
Francke-Grosmann, H. (1967). Ectosymbiosis in Wood-Inhabiting Insects. In Symbiosis (ed. by S.M. Henry), Vol. 2 – Associations of Invertebrates, Birds, Ruminants and Other Biota, pp. 141-206. Academic Press, New York.
Kuhnholz, S. (2004) Chemical ecology and mechanisms of reproductive isolation in ambrosia beetles, Simon Frazer University, Burnaby.
Mueller, U.G., Gerardo, N.M., Aanen, D.K., Six, D.L., & Schultz, T.R. (2005) The evolution of agriculture in insects. Annual Review of Ecology and Systematics, 36, 563-595.