Environmental heterogeneity governing river macrophyte beta diversity in Europe is scale- and context-dependent

Content
A comprehensive understanding of how and to what extent beta diversity and community-environment relationships vary at various spatial scales is important to derive realistic forecasts of the future of freshwater communities.
Objectives
We assessed how total beta diversity and its two components (species replacement and species richness differences) of river macrophytes change among and across Portugal, Poland, Germany, Denmark and Finland. We further addressed which and how environmental and spatial gradients explain compositional variation of macrophyte communities among European regions and differences in beta diversity across the continent.
Methods
We employed generalized linear mixed models, permutational analysis of multivariate dispersions and generalized dissimilarity modelling to investigate beta diversity of river macrophytes among study regions, whereas generalized additive model for location, scale and shape was used to research patterns across regions.
Results
Macrophytes beta diversity and its replacement component tended to increase or were not significantly related to latitude at regional scales, whereas total beta diversity showed a negative latitudinal effect across study regions in Europe. This finding suggests that patterns predicted at one spatial scale may not necessarily be predicted at other scales. Species replacements also dominated over species richness differences in explaining beta diversity patterns across all the study regions. However, different environmental variables contributed to beta diversity of river macrophytes among the study regions.
Conclusion
Environmental heterogeneity manifested by altitude range and geodiversity was the major driver of total macrophyte beta diversity in Europe. These results highlight how spatial scale and context-dependency across different regions have a profound influence on how river macrophytes respond to their environment.