Bark and ambrosia beetles are a remarkably diverse group of weevils with extraordinary variation in ecological adaptations. As one of the most species rich subfamilies among the advanced weevils, they dominate any forest insect community around the globe. While the most famous features of these beetles are vast outbreaks and damage to timber and other forest products, coordinated tree killing is only one of many kinds of unusual lifestyles. The colonization and reproduction in concealed niches in dead woody plant tissue has for instance led to multiple origins of fungus farming, sometimes with modifications of mating systems to allow close inbreeding by sibling mating, which likely facilitated multiple super-radiations similar to those observed for pine and spruce associated bark beetles. However, knowledge about the timing and ecological circumstances under which each of the largest radiations originated is highly uncertain, due to the lack of phylogenetic resolution for this beetle group. Establishing an accurate phylogenetic hypothesis is therefore of paramount importance in enabling detailed inference about these great radiations. Resolution of hyperdiverse groups is a daunting task, however, and only a large scale phylogenomic approach can provide sufficient data to enable reconstruction of evolutionary transitions at different hierarchical levels. Comparative analyses of transitions to fungus farming are dependent on detailed data on communities of symbiotic fungal microbes. We will therefore carry out the first quantitative inference of the evolution of a symbiosis between beetles and communities of fungi, to demonstrate the composition of different fungal species associated with a single beetle, and the variation in community composition across different groups of beetles. Our novel approach thus makes a ground-breaking example for quantitative studies on the evolution of diverse symbioses, particularly so in light of interaction with vascular host plants.
