Distribution records and endemism of Japanese Collembola
To document the distribution records of Collembola in Japan, we referred to the Catalogue of the Insects of Japan (Editorial Committee of Catalogue of the Insects of Japan, 2020. Touka Shobo, Fukuoka) as well as the Collembola catalogues of neighboring regions: Korea (Park and Lee, 2014. National List of Species of Korea: Collembola, Diplura, Protura. National Institute of Biological Resources, Incheon), China (Zhao et al., 1997. Publication of the Itako Hydrobiological Station, 9: 15–40), and Taiwan (Cheng et al., 2022. ZooKeys, 1123: 123–146). Species listed in the Catalogue of the Insects of Japan without distribution records outside Japan, and also not recorded in the catalogues of Korea, China, or Taiwan, were classified as "tentative endemic species." All other species were classified as "tentative non-endemic species." For species with no distribution records, those with type localities in Japan were treated as "tentative endemic species."
Subsequently, the distribution of the identified "tentative endemic species" was examined using the Global Biodiversity Information Facility (GBIF; GBIF.org, 2023. https://www.gbif.org; accessed May 31–July 8, 2022). Species without occurrence data from outside Japan were designated as "endemic species," while those with such data were classified as "non-endemic species." The numbers and proportions of endemic species were then calculated. The analysis focused on species-level data, treating a single species as one unit regardless of whether one or multiple subspecies were recorded.
Species with uncertain distribution in Japan, such as those marked with a "?" in the Catalogue of the Insects of Japan or annotated as "unidentifiable," were excluded from the analysis. However, species with "cf." in their names, indicating uncertainty in species identification, were not excluded.