Exploring an ecological puzzle: Why do certain insects form dynamic associations with multiple fungal partners?

Microbial symbioses facilitate ecological and evolutionary innovations in herbivorous insects.

The success of herbivores is often attributed to their partnership with microbial symbionts, allowing them to adapt to specific ecological niches. For instance, wood-boring bark beetles rely entirely on fungi to alleviate nutrition deficiency and survival.

While most aggressive bark beetles that kill vigorous trees have a stable mutualistic relationship with a few fungi, the Eurasian spruce bark beetle (ESBB), Ips typographus that kills conifers in Europe, exhibits a unique pattern.

ESBB consistently co-occur with different lineages of multiple fungi and has developed a dynamic relationship with them.

Thus, the research question arises: why has ESBB adapted to a dynamic multipartite relationship without strict dependence on single species?

Experimental manipulation of fungal symbionts will be carried out to study their effects on ESBB fitness, focusing on the five most dominant and frequent fungal symbionts.

Additionally, physiological adaptations in both beetles and fungi will be studied to understand the mechanism of microbial inheritance in multipartite symbioses.

The hypothesis is that those dynamic fungi provide flexibility in niche adaptation for ESBB, as they potentially supplement nutrition to all life stages of ESBB.

This study is expected to yield novel insight into the fitness advantage of insects having loose partnerships with multiple fungal partners.