Data from: No biotic homogenisation across decades but consistent effects of landscape position and pH on macrophyte communities in boreal lakes

It has been predicted that spatial beta diversity shows a decreasing trend
in the Anthropocene due to increasing human impact, causing biotic
homogenisation. We aimed to discover if vascular aquatic macrophyte
communities show different spatial patterns in beta diversity in relation
to land use and environmental characteristics in different decades from
1940s to 2010s. We aimed to discover if spatial structures differ between
species-, phylogeny- and functional-based beta diversity. We used
presence-absence data of aquatic macrophytes from five decades from small
boreal lakes. We utilized generalised dissimilarity modelling to analyse
spatial patterns in beta diversity in relation to environmental gradients.
We found that lake elevation and pH were the most important variables in
each decade, while land use was not particularly important in shaping beta
diversity patterns. We did not find signs of a decreasing trend in spatial
beta diversity in our study area during the past 70 years. We did not find
signs of either biotic homogenisation or biotic differentiation
(taxonomic, phylogenetic or functional). Vascular aquatic macrophyte
communities showed only slightly different beta diversity patterns in
relation to human impact across decades. The patterns of different facets
of beta diversity diverged only slightly from each other. Lake position in
the landscape, reflecting both natural connectivity and lake
characteristics, explained the patterns found in beta diversity, probably
because our study area has faced only modest changes in land use from
1940s to 2010s when compared globally. Our study highlights the fact that
biotic homogenisation is not an unambiguous process acting similarly at
all spatial and temporal scales or in different environments and different
organism groups.