COS 210-6 - Bryophytes and vascular plants show differing taxonomic and functional biodiveristy patterns along latitudinal gradients in bogs and fens

Background/Question/Methods

Species diversity typically decreases towards the poles, but this pattern does not hold for all ecosystems nor plant functional groups. Studying distinct groups simultaneously (e.g., vascular and bryophytes) in ecosystems where they are abundant, such as peatlands, should provide insight on factors governing diversity and should help predict compositional changes in response to environmental variations. The objective of our study was to evaluate the influence of latitude, abiotic variables, and peatland types (bogs vs. fens) on vascular and bryophyte diversity. Inventories were conducted in 380 peatlands in northeastern Québec (49° to 54° N). We evaluated changes in α- (species richness and functional dispersion) and β-diversity (local contribution to taxonomic and functional β-diversity indices) in response to latitude, continentality, climate, and local abiotic variables for both plant groups using generalized linear models. We also evaluated the effects of these variables on taxonomic and functional composition using variance partitioning by redundancy analysis (RDA).

Results/Conclusions

We found that bryophyte richness increased towards the north, while β-diversity decreased towards the north, implying that the latitudinal increase in bryophyte biodiversity only applies to α-diversity. Vascular richness showed contrasting patterns in bogs and fens in response to latitude. In fens, vascular richness decreased towards the north, and inversely in bogs in which functional diversity was also higher than in fens. β-diversity decreased towards the north in bog bogs and fens, although fens maintained higher β-diversity throughout the whole gradient. Higher latitudes were therefore associated with taxonomic and functional homogenization for both plant groups in both habitats. Latitude thus has homogenous effects on β-diversity but contrasting effects on α-diversity in both habitats and for both species groups. Taxonomic and functional diversity and composition of both vascular and bryophyte species were primarily structured by differing local conditions in bogs and fens related to water availability and peat thickness, while bioclimatic variations played a secondary role. Therefore, both plant groups and habitats are affected differently by environmental factors, and future studies and policies should include these differences when evaluating the effects of environmental changes on biodiversity and planning conservation.