Recorded moth communities showed no clear change in spatial similarity at 22 Finnish light-trap locations between 1993–2002 and 2010–2019

We tested whether moth communities at the same Finnish light-trap locations became more similar. We used the open FinBIF archive dated 21 October 2026. The fixed panel had 22 locations, 361 location-years and 1,737,127 moths identified to species. We compared 1993–2002 with 2010–2019. At each location, we averaged annual species catch shares with equal year weights. Mean Hellinger squared dissimilarity across 231 location pairs fell from 0.3940 to 0.3903. The change was −0.0037 on a zero-to-one scale. A joint bootstrap of 100 km spatial groups and three-year blocks gave a nominal 95% interval of −0.0423 to +0.0396. Bray–Curtis and equal-catch comparisons also gave intervals that included zero. Coverage, minimum-year, full-year and cyclic-species checks gave the same general result. The test therefore established neither spatial homogenization nor stable communities. Opposing species contributions gave a small net change. An independent source calculation reproduced all main annual species counts and period profiles. The panel covers southern and central Finland and selects locations with long records. Light-trap catches depend on activity, detection and methods. These data do not identify a climate cause or a national trend. The package contains the source extract, provenance, code, plan, results, bootstrap draws and figures.

moths · Finland · species composition · biotic homogenization · light traps · fixed panel · null result · reproducibility