Fungivore host-use groups from cluster analysis: patterns of utilisation of fungal fruiting bodies by ciid beetles

1. Ciid beetles typically live and breed in the fruiting bodies of lignicolous basidiomycete fungi. This study was undertaken to address the lack of an objective examination of patterns of host use by ciids. 2. Cluster analysis of ciid host-use datasets from Britain, Germany, North America, and Japan, and subsequent cross-dataset comparisons, demonstrated the existence of ciid host-use patterns of wide geographical occurrence. These patterns were formalised as ciid host-use groups. 3. Six Holarctic ciid host-use groups, and two host-use subgroups, were identified, and are described. Each host-use group comprises an assemblage of fungal genera and the breeding ciids that it supports. Each taxon belongs to only a single host-use group, but may be associated with several members of that group. There is a strong tendency for closely related taxa to belong to the same host-use group. 4. It is suggested that ciid host-use groups are defined ultimately by host chemistry, with the ciids that belong to a particular group recognising, and responding positively to, emitted volatiles characterising the fungi belonging to that group. 5. The idea of the host-use group bears comparison with the concepts of niche and guild, but is not equivalent to either. 6. Ciid host-use groups have a valuable role to play in underpinning future studies of ciid ecology, also the systematics of both ciids and their fungal hosts.