Abstract
Despite important progress, uncertainty persists regarding the ecological forces driving microbial community assembly. Here, we present the first study to use phylogenetic information to interpret the structure and diversity of diatom communities. We examined local phylogenetic divergence and beta- phylogenetic diversity in a large dataset of 595 freshwater benthic diatom communities and we investigated how this diversity is influenced by gradients in nutrients, pH, organic matter and catchment size. Overall, we found that diatom communities were phylogenetically clustered, i.e. species within communities were more closely related than expected by chance. Phylogenetic clustering was stronger in nutrient-poor environments and in sites with a small catchment area. The variation of the phylogenetic beta-diversity index was much better explained by space and environment than the variation of the taxonomic index was. Both approaches detected a significant effect of environment and space on diatom community turnover. Our results support the view that diatom communities are primarily shaped by environmental filtering, in particular by nutrient availability. Moreover, they highlight the importance of considering dispersal-related processes and the depth of phylogenetic signal in functional traits when interpreting patterns of diversity.
Highlights
Understanding the mechanisms which determine the generation of biodiversity and the structure of biological communities is a major concern of ecology[1]
We found that SES-mean pairwise distance index (MPD) increases with upstream catchment area (UCA), total organic carbon (TOC) and pH (Table 1, Fig. 3)
Nutrients were the most important predictor (LMG = 0.12, CI = [0.08; 0.17]). We found that both nutrients and UCA have a positive effect on SES-mean nearest taxon distance index (MNTD) (Table 1, Fig. 3)
Summary
Understanding the mechanisms which determine the generation of biodiversity and the structure of biological communities is a major concern of ecology[1]. Despite important progress, uncertainty persists regarding the ecological forces driving diatom community assembly These questions have traditionally been addressed using a taxonomic perspective of diversity where taxa are regarded as independent entities. Since functional diversity offers more insights into the processes at the origin of biodiversity[15,16], a stronger emphasis has been placed on trait-based ecology in recent years[17]. Given their large diversity and their microscopic size it is challenging to collect trait data for diatoms, and a comprehensive trait database for ecological studies is still missing[18]. By integrating the evolutionary history of the species, phylogenetic diversity can provide substantial insights into the ecological processes underlying community structure and composition[23,24]
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