- An unusual data set of Plecoptera, very sensitive aquatic insects, allow diversity changes to be estimated for 175 streams in the Czech Republic between two periods, 1955–1960 and 2006–2011.
- Substantial overall declines in Plecoptera biodiversity were found. Three-quarters of the species studied declined in their frequency of occurrence, 48% of which were estimated have undergone a reduction of >30%. Overall, streams either at lowland or submontane altitude, particularly large rivers, lost the most species. A significant decrease in local species biodiversity was found in streams up to 700 m a.s.l., especially in small rivers.
- The taxonomic dissimilarity between contemporary and previous assemblages increased from montane to lowland altitudes (from ˜30 to ˜70%) and was the same in streams of different size (˜50%). Partitioning of dissimilarity showed that the overall change in dissimilarity was primarily driven by changes in species richness; however, species replacement was not negligible.
- The results demonstrated that aquatic insect biodiversity (Plecoptera in particular) is substantially declining in Europe, probably to a similar or greater extent than terrestrial insects, with potential implications for biodiversity of running waters. Plecoptera showed a complex response to habitat change, including loss of pollution-sensitive species and habitat-specialists as well as common species, which, in some cases, counterbalanced their losses by concurrent colonisation of new sites.