Environment regimes play an important role in structuring trait- and taxonomy-based temporal beta diversity of riverine diatoms

A sound understanding of the community changes over time and its driving forces is at the centre of biodiversity conservation and ecology research. In this study, we examined: (i) the relative roles of turnover and nestedness components to trait- and taxonomy-based temporal beta diversity of riverine diatoms; (ii) whether trait-based temporal beta diversity provides complementary information to taxonomy-based temporal beta diversity; (iii) the relative roles of hydrology (e.g. discharge, antecedent precipitation index), metal ions (e.g. Mg2+, Si2+) and nutrients (e.g. nitrogen, orthophosphate) to the both facets of temporal beta diversity and their components (i.e. total beta diversity, turnover and nestedness); and (iv) whether inclusion of environment regimes increase their explained variations. A total of 338 daily samples of riverine diatom communities were collected. We employed Mantel tests to evaluate the complementarities between trait- and taxonomy-based temporal beta diversity. Using distance-based redundancy analysis (db-RDA) and variation partitioning, we investigated the relative roles of hydrology, metal ions and nutrients to each facet of temporal beta diversity and its components. Correlations between trait- and taxonomy-based temporal beta diversity and their components were weak, which showed their complementary ecological information. Taxonomy-based total beta diversity had a high contribution by turnover component, whereas trait-based total beta diversity was largely driven by nestedness component. Results of variation partitioning demonstrated that the pure and shared fractions of hydrology, metal ions and nutrient differed among the components of trait- and taxonomy-based temporal beta diversity. Furthermore, addition of environment regimes could dramatically increase the explained variation of temporal beta diversity and its components. Synthesis. Our results highlighted the importance of the two facets of temporal beta diversity as well as their decomposition for exploring diversity patterns of riverine diatoms in relation to abiotic factors, particularly the environment regimes. Although a high temporal taxonomic divergence was detected, the high level of temporal trait convergence indicated that species turnover with similar biological traits occurred during our study period. Our study, for the first time, provides a new perspective into temporal beta diversity of daily riverine diatom communities, which has not yet been documented by previous freshwater studies.