Advances in Biology & Earth Sciences

The paper presents new data on the population structure of harvestmen (Arachnida, Opiliones) in the Yew-Boxwood Grove of the Caucasian State Natural Biosphere Reserve (Russia) following the invasion of the box tree moth (Cydalima perspectalis (Walker, 1859), which caused the mass dieback of boxwood and substantial changes in forest cenosis parameters. Field studies were conducted in 2017, 2018, 2021 and 2023 at a broad-leaved boxwood site, as well as at a yew–beech forest site with cherry laurel understory. Sampling was carried out using Barber pitfall traps installed on permanent plots. The results showed that the species composition of harvestmen generally remained stable. After a pronounced decline in abundance during 2015-2018 (down to 4.64-6.39 specimens/100 trap-days per season), a significant recovery was observed in 2021 (26.93 specimens/100 trap-days), approaching the pre-invasion level recorded in 2006. In 2023, abundance decreased again, likely due to extremely dry conditions. At the yew-beech forest site, catchability also declined compared to 2006. The findings indicate that changes in forest structure and microclimatic conditions strongly influenced harvestmen population dynamics, while the subsequent increase in abundance reflects the gradual recovery of the forest ecosystem after the ecological disturbance.