May–October ground-beetle catches showed no clear mean gain in similarity of species shares across seven UK sites in 1994–2013

We tested whether ground-beetle catches became more similar between fixed UK Environmental Change Network sites. We compared qualifying years in 1994–2003 and 2004–2013. The main sample has 115 named species, 15 transects, 231 complete transect-years and seven sites. We adjusted catches for monthly trap effort and used all named species in the selected panel. Mean Bray–Curtis distance between site species shares fell from 0.794 to 0.763. The change was −0.031, with a 95% site-and-year resampling interval of −0.125 to +0.077. Thus, the data do not establish a mean gain in similarity across these sites. The mean change within sites was larger: the distance between period profiles was 0.268. Effort, quality, season, annual weight and dominant-species checks gave changes from −0.010 to −0.031; all site-and-year intervals included zero. With sites fixed, a secondary year-only interval depended on the year-block choice. A fixed-total sampling benchmark also shows why occurrence and species-share measures can give different signs. Pitfall catches measure activity and density together. The sites are not a random UK sample, and missing years differ between transects. We preserve original source data, provenance, code, all estimates, figures and a clean reproduction check.

Carabidae · ground beetles · Environmental Change Network · species composition · spatial similarity · biotic homogenization · pitfall traps · survey effort · reproducibility