QuestionsHow do two distant mountain ranges differ in their vegetation-environment relationships, overall species composition and its variability and species richness of vascular plants and bryophytes in alpine fens and bogs? Is the floristic difference consistent along the acidity-alkalinity gradient? LocationWest Carpathians (Poland, Slovakia) and Swiss Alps. MethodsVascular plant and bryophyte species compositions and environmental characteristics were sampled along the large acidity-alkalinity gradient within the alpine belts. PERMANOVA was used for testing floristic differences between the regions, DCA for the patterns description, CCA for testing the vegetation-environment relationships and linear models for testing the local species richness determinants. Compositional -diversity (rate of compositional turnover) and regional species pool were compared using PERMDISP and sample-based rarefaction curves. ResultsMost floristic variation was explained by water pH in both regions. Macroclimate was the second most important gradient in the Alps, correlating with the second DCA axis delimiting the moderately poor brown-moss fens from the Sphagnum bogs. The species composition differed significantly between the regions in all three pH classes, expect for bryophytes in the middle pH class. Bryophytes exhibited higher similarities between the regions, except in acidic mires. Vascular plant composition differed most in the middle pH class. The local species richness was predominantly determined by pH, except for bryophytes in the Alps. As compared to bryophytes, vascular plant local species richness was affected by more factors and showed a clear linear response to pH. Within the particular pH classes, there were few differences in local species richness, compositional -diversity and regional species pool between the two mountain ranges. ConclusionsThe pattern in inter-regional floristic dissimilarities differs between bryophytes and vascular plants, probably because of better dispersal ability of bryophytes, and different causes of these dissimilarities: lower mass effect at extreme ends of the acidity-alkalinity gradient in the case of vascular plants and higher compositional -diversity of acidic mires in the case of bryophytes. Contrary to previously explored alpine springs of the same regions, local species richness and composition were determined rather by pH than mineral richness, and all patterns were more consistent between the regions and the taxonomic groups.