Effects of habitat surrounding environmental factors on the distribution of four Osmia species (Hymenoptera: Megachilidae) in South Korea

Osmia species are widely used as pollinators in apple orchards in South Korea, but their populations are declining globally due to climate change, urbanization, and natural predators. This alarming trend underscores the urgent need for research on the environmental and climatic factors that influence Osmia species habitats. In this study, we investigated the distribution and environmental influences of four Osmia species (O. cornifrons, O. pedicornis, O. taurus, and O. satoi). We monitored their primary occurrence areas across South Korea and collected landscape, elevation, and climate data within a 50-m radius of these areas from 2021 to 2023. Subsequently, we assessed key environmental factors using a linear mixedeffect model. The Osmia species distribution between 2021 and 2023 was as follows: O. pedicornis (56.64%), O. cornifrons (21.23%), O. satoi (11.13%), and O. taurus (11%). The O. pedicornis population exhibited a significant annual increase, rising from 39.74% to 72.85%. Conversely, the O. cornifrons and O. satoi populations gradually decreased, declining from 33.62% to 12.76% and 22.43% to 1.8%, respectively. The linear mixed-effect model analysis revealed that the four species exhibited significant relationships with environmental factors, such as coniferous forests and altitude. O. cornifrons demonstrated an increased distribution at higher altitudes, latitudes, and humidity levels. In addition, O. pedicornis exhibited similar trends, demonstrating a preference for habitats with water as a prominent landscape cover. Through this, it can be inferred that both O. cornifrons and O. pedicornis share ecological preferences for habitats characterized by water accessibility, which significantly influences their distribution and habitat selection. Despite the significant relationships observed, the habitat preferences of Osmia species were shaped each by specific environmental conditions, which limit the generalizability of these results. Nonetheless, these findings provide important insights for predicting habitat shifts caused by climate change and formulating conservation strategies for Osmia species.