Local and biogeographical determinants of the diversity and structure of invertebrate communities in rot holes of ash, Fraxinus excelsior

O_LIVeteran trees are biodiversity hotspots, providing a range of microhabitats, including tree hollows or rot holes in trunks, which support a large diversity of invertebrates including threatened species. Each rot hole is a unique microcosm, with variable biotic and abiotic characteristics enabling their use by many invertebrate taxa. C_LIO_LIMost previous studies describing the invertebrate communities of rot holes and the factors determining their structure focus on a narrow range of invertebrate taxa, and many host tree species remain unexplored. European ash (Fraxinus excelsior L.) is one of Europes most threatened deciduous tree species due to the spread of ash dieback disease, but the potential impact of these losses on the invertebrate communities that inhabit ash is poorly understood. C_LIO_LIInvertebrates were sampled and identified to family level from 14 sites across Wales and western England, and major physical characteristics of each rot hole and sample site were assessed (e.g., habitat type, altitude, maximum site temperature). C_LIO_LIAsh rot hole invertebrate communities were highly diverse with a range of threatened taxa, including some undescribed or new to the region. There was large variation in both measured rot hole characteristics and the invertebrate communities between individual rot holes, sites and habitats. Both tree-specific and biogeographical factors significantly influenced invertebrate diversity and community structure, suggesting that sustaining the heterogeneity of ash rot holes across a range of locations is required to support saproxylic invertebrate diversity. C_LIO_LIWith increasing ash veteran tree vulnerability, sustaining these vital habitats and their associated invertebrate communities is a conservation imperative. This study has demonstrated that considering heterogeneity in both habitat characteristics and landscape context will be crucial when conserving these communities. C_LI