Pozsgai, G., Baird, J., Littlewood, N.A., Pakeman, R.J. & Young, M.R. (2016) Long-term changes in ground beetle (Coleoptera: Carabidae) assemblages in Scotland.Ecological Entomology, 41(29, 157-167. DOI:10.1111/een.12288 (IF2016 1,771; Q1 Entomology)
1. One-way, directional changes in both plant and animal associations are likely to be occurring as a result of changing climate. Current knowledge of long-term cycles in insect communities is scarce, and therefore it is difficult to assess whether the observed changes in insect communities are the first part of a long-term trend or parts of normal cycles.
2. In this study multivariate methods were used to describe the trends in ground beetle (Coleoptera: Carabidae) assemblages over an 18-year (1994–2011) period at two Scottish sites. In order to have a deeper insight into the underlying processes, both environmental factors and the species driving the detected changes were investigated.
3. In four out of the six sample transects, insect community compositions showed trends rather than fluctuating patterns. Hierarchical cluster analysis also revealed a clear separation, after accounting for sampling location and broad habitat, between early and later years of sampling. Decreasing annual maximum temperatures and increasing precipitation were identified as the main environmental drivers. Although increased rainfall was expected to be beneficial for hygrophilous species, in the transects in this study generalist species increased in dominance.
4. The increasing importance of generalists, in the communities studied here, underlines the vulnerability of the specialist species and urges greater effort in their conservation. Assemblage changes along different trajectories at the sites in the present study could only be tracked using multivariate methods; commonly used diversity indices proved to be unsatisfactory. Therefore, the exclusive use of simple diversity indices should be discouraged and multivariate methods should be preferred in environmental assessments and conservation planning.