Abstract
Biodiversity has traditionally been quantified using taxonomic information but the importance of also considering its functional characteristics has recently gained an increasing attention among microorganisms. However, studies exploring multiple aspects of taxonomic and functional diversity and their temporal variations are scarce for diatoms, which is one of the most important microbial groups in aquatic ecosystems. Here, our aim was to examine the taxonomic and functional alpha and beta diversities of diatoms in a coastal rock pool system characterized by a naturally high environmental heterogeneity. We also investigated the temporal differences in the diversity patterns and drivers. The relationship between the species richness and functional dispersion was temporally coherent, such that species-poor communities tended to be functionally clustered. The trend between the species richness and taxonomic uniqueness of community composition was temporally inconsistent, changing from negative to non-significant over time. Conductivity or distance to the sea or both were key determinants of species richness, functional dispersion, and uniqueness of community composition. The increase of community dissimilarity with an increasing environmental distance was stronger for the taxonomic than the functional composition. Our results suggest that even minor decreases in the species richness may result in a lowered functional diversity and decreased ecosystem functioning. Species-poor ecosystems may, however, have unique species compositions and high contributions to regional biodiversity. Despite changing the species compositions along the environmental gradients, communities may remain to have a high functional similarity and robustness in the face of environmental changes. Our results highlight the advantage of considering multiple biodiversity metrics and incorporating a temporal component for a deeper understanding of the effects of environmental changes on microbial biodiversity.
Highlights
During the era of ongoing global change, the need to understand biodiversity patterns has increased (McGill et al, 2015)
We investigate whether there is a relationship between species richness and taxonomic uniqueness of community composition, testing the idea that communities with certain species diversity levels would contribute more strongly than others to the overall taxonomic beta diversity
We explored the relationships between species richness and functional dispersion or local contributions to beta diversity (LCBD) with linear regression
Summary
During the era of ongoing global change, the need to understand biodiversity patterns has increased (McGill et al, 2015). Beta diversity should be considered to understand the mechanisms influencing regional biodiversity and for guiding efforts to conserve it (Socolar et al, 2016). Considering only the taxonomic characteristics of communities ignores the different functions that species have in an ecosystem. The inclusion of the functional characteristics (i.e., traits) can provide a more effective way to describe diversity (Mouchet et al, 2010). Studying functional diversity allows comparisons among different ecosystems, such as rock pools and other aquatic ecosystems, to be made despite the differences in the taxonomic compositions. For a deeper understanding of the patterns and processes influencing communities, using trait-based approaches in combination with taxonomic information may be useful (Leibold and Chase, 2018)
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