Spatial congruence between ecoregions and littoral macroinvertebrate assemblages

Abstract

The usefulness of ecoregions for discriminating between littoral macroinvertebrate assemblages of 363 Swedish lakes was examined. A relatively good correspondence was found between ecoregion delineations and macroinvertebrate assemblages of the lake littoral zone. Variables describing macroinvertebrate assemblages (abundance, taxon richness, diversity, and Sørensen similarity) had significantly different values in the 6 ecoregions, but the most marked differences occurred between the middle and southern boreal regions, coinciding with the approximate location of the ecotone delineating the northern coniferous (taiga) and southern deciduous forests. Macroinvertebrate assemblages of lakes in the south were generally more diverse, having more taxa, whereas lakes in the north in general and in the arctic–alpine complex in particular were characterized by low richness and the presence of 2 plecopterans, namely Diura nanseni (Kempny) and Capnia atra Morton. Twenty-five variables made significant contributions to explaining the variance among species assemblages. In the constrained ordination of taxa and environmental factors by canonical correspondence analysis, variables indicative of geographic position (latitude and longitude), ecosystem type (water color and lake surface area), and habitat type (pebble substratum) were among the first 5 variables selected. Discriminant analysis of 25 environmental variables and 6 UPGMA (flexible β unweighted pair-group method using arithmetic averages) groups classified 64% of the sites to the correct group.