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Conference Papers Year : 2017

Drivers of Stream diatom beta-diversity from local to global scales


The taxonomic composition of a community results from an interplay of regional (dispersal and species pool) and local (species sorting) processes and a key question in community ecology is to understand the relative influence of these processes along gradients. β-diversity might represent a potential key to contribute to this question. Diatoms play a central role in aquatic ecosystems and more and more researchers focused their attention on finely understanding the mechanisms that govern their community assembly. It is now accepted that the biogeographical distribution of stream diatoms depends mainly on environmental heterogeneity, anthropogenic impacts and dispersal-related processes. Today we only have a limited understanding of how species sorting and dispersal-related processes interact to affect diatom species distribution, and of how these potential interactions are modulated by the geographic scale (environmental heterogeneity) and by anthropogenic stressors. In this study, we explored the β-diversity evolution of stream diatom communities from local to global scales, across different levels of nutrient enrichment, with a dataset encompassing 3000 samples from France and the US. According to the arguments developed before, we tested four main hypotheses: (1) β-diversity in diatom communities increases from local to larger scales, as environmental heterogeneity increases. (2) β-diversity in natural conditions is always higher than β-diversity in communities under high nutrient levels, regardless of scale. (3) In unimpacted conditions, β-diversity is mainly controlled by species-sorting and the relative contribution of this process is expected to increase from local to larger scales. (4) In impacted conditions, species-sorting influence should be tenuous and constant across spatial scales, allowing to detect the signal of dispersal-related processes. Our results highlight that beta-diversity increases from local to global scales and is always higher in unimpacted conditions than in impacted ones. After extracting the effect of gamma diversity with null models, we detected significant changes in the relative impact of local community assembly processes vs. regional processes according to the scale of observation. The relative importance of species-sorting increases simultaneously with the scale and this phenomenon is particularly pronounced for unimpacted environments. In impacted conditions, species-sorting influence is weakened and we detected the signal of dispersal-related processes. Our results generate novel insights into the main mechanisms driving beta-diversity patterns.
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Dates and versions

hal-02606786 , version 1 (16-05-2020)



Thibault Leboucher, W.R. Budnick, Aurélien Jamoneau, Sébastien Boutry, J. Soininen, et al.. Drivers of Stream diatom beta-diversity from local to global scales. 1st International Conference on Community Ecology, Sep 2017, Budapest, Hungary. pp.44. ⟨hal-02606786⟩


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