This is the datasets and R script for our manuscript titled "The spatial extent and the dispersal strategy of species shape the occupancy frequency distribution of stream insect assemblages." Study area and sampling of Mecsek_species_Szivaketal.xlsx data The study area is situated in the Mecsek Mountains in Hungary. Stream insects were collected using the kick and sweep sampling technique. A hand net with a frame width of 25 cm and a mesh size of 1000 µm was employed. The collection involved disturbing an area of 0.25 × 0.25 m. We employed a stratified random multihabitat sampling procedure. We collected 20 sample units from the major microhabitats in proportion to their occurrence within the reaches. Each sample unit was individually processed and sorted in the laboratory to ensure thorough and accurate analysis. Disperse_trait_Szivaketal.xlsx data is based on DISPERSE database (Sarremejane et al., 2020) Methods for microhabitat_coverage_reach_transect.xlsx: Prior to sampling, we divided each 100 m long reach into 20 transects of comparable length and created microhabitat coverage maps. Using these maps, we assessed the proportionate coverage of different microhabitat types within each reach References: Sarremejane, R., Cid, N., Stubbington, R., Datry, T., Alp, M., Cañedo-Argüelles, M., Cordero-Rivera, A., Csabai, Z., Gutiérrez-Cánovas, C., Heino, J., Forcellini, M., Millán, A., Paillex, A., Pařil, P., Polášek, M., Tierno de Figueroa, J. M., Usseglio-Polatera, P., Zamora-Muñoz, C., & Bonada, N. (2020). DISPERSE, a trait database to assess the dispersal potential of European aquatic macroinvertebrates. Scientific Data, 7(1), 386. https://doi.org/10.1038/s41597-020-00732-7