Spatial and local environmental factors outweigh geo-climatic gradients in structuring taxonomically and trait-based β-diversity of benthic algae

Aim Understanding the variation in biodiversity and its underlying drivers and mechanisms is a core task in biogeography and ecology. We examined (a) the relative contributions of species replacement (i.e., turnover) and richness difference (i.e., nestedness) to taxonomically and trait-based β-diversity of stream benthic algae; (b) whether these two facets of β-diversity are correlated with each other; and (c) the relative contributions of local environmental, geo-climatic and spatial factors to the two facets of β-diversity and their components. Location Hun-Tai River Basin, northeastern China. Taxon Stream benthic algae. Methods A total of 157 sites were sampled. Mantel tests were used to examine the complementarities between the two facets of β-diversity and their components. Distance-based redundancy analysis and variation partitioning were utilized to investigate the relative contributions of local environmental, geo-climatic and spatial factors to each facet of β-diversity and their components. Results Weak correlations between taxonomically and trait-based β-diversity and their components were detected, which indicated complementarity of ecological information. Taxonomically based total β-diversity was largely driven by turnover, whereas trait-based total β-diversity was more driven by nestedness. Variation partitioning results indicated that local environmental and spatial factors contributed more than geo-climatic variables to the total explained variation in taxonomically and trait-based β-diversity. Main conclusions Different facets of β-diversity and their decomposition are important for understanding diversity patterns of benthic algae relative to abiotic factors. A high level of trait-based convergence among benthic algae communities, despite high taxonomic divergence, demonstrated turnover of species with similar biological traits across our study region. Our study provides a trait-based insight into stream benthic algae communities, which was less documented by previous freshwater studies that focused on regions undergoing recovery following human disturbances.