Ten-year host-use patterns of longicorn beetles in experimental logs of conifer and broad-leaved trees in central Hokkaido, northern Japan

Deadwood provides critical habitats for saproxylic beetles, but knowledge of the host-use patterns of saproxylic beetles remains limited. We performed a long-term experiment to examine the host-use patterns of longicorn beetles in central Hokkaido, northern Japan. We exposed freshly cut logs of conifer and broad-leaved trees to beetle oviposition in conifer plantations and broad-leaved natural forests during one active season. Afterwards, we transported these logs to a nursery, enclosed in emergence traps, and followed beetle emergence for 10 years. During the experimental period, more than six longicorn beetle species emerged from each tree species. Dominant beetle species differed among tree species, particularly between conifer and broad-leaved logs, suggesting that retaining broad-leaved trees in conifer plantations can increase the overall diversity of longicorn beetles. There was a turnover of species as wood decayed. Annual changes in the number of beetles emerged, which were examined for the species collected with >10 individuals, showed that seven species first emerged in 1–2 years after logging, their abundance peaked in the 2nd–4th year, and beetles emerged until the 2nd–6th year. This suggests that these species oviposited on freshly felled logs and exhibited a single generation. In contrast, 6 species emerged only after the 3rd year, their abundance peaked between the 4th–8th year and they emerged until the 8th–10th year. Beetle emergence from control logs, which were enclosed in emergence traps immediately after logging, suggests that some of these six species oviposited after the logs being enclosed in the traps and had multiple generations.