Regional gradient analysis of freshwater biota: do similar biogeographic patterns exist among multiple taxonomic groups?

Aim To examine if different groups of freshwater organisms show concordant distribution patterns at large spatial scales. Location Northern Europe: Denmark, Sweden, Norway, Finland. Methods I analysed provincial distribution records of macrophytes, dragonflies, stoneflies, dytiscid beetles and teleost fishes in northern Europe. I conducted multivariate analyses, including two-way indicator species analysis (TWINSPAN), canonical correspondence analysis (CCA) and Mantel test to reveal biogeographical patterns and the degree of concordance in the distribution patterns among taxa. Results TWINSPAN and Mantel tests indicated that broadly similar biogeographical patterns existed among the taxonomic groups. The results of CCA confirmed that variation in provincial species composition was generally related to climatic variation along latitudinal and altitudinal gradients. However, variation partitioning revealed that less than 50% of variation in the distribution patterns of each taxonomic group was accounted for by the climatic and geographical variables. Main conclusions The distribution patterns of most taxonomic groups were strongly concordant and related to provincial climate and geographical location. Such patterns suggest that large-scale factors determine not only provincial species combinations, but also express severe constraints on the composition of local communities. Therefore, these factors should also be considered in studies on the structure and conservation of local freshwater systems.