Beta-diversity partitioning and drivers of variations in tropical fish community structure in central India

Flow regulations, human activities and drying events have been shown to drive diversity patterns of stream fish communities globally. Along with alpha-diversity distributions across space and time, study of beta-diversity patterns provides a deeper understanding of the mechanisms and processes of overall diversity distributions. It has been shown that water flow conditions can determine the beta-diversity patterns in stream fish communities: in general, perennial habitats are more similar, while intermittent and regulated conditions tend to increase dissimilarities among sites. However, it is not clear whether these patterns result from changes in abundance replacement or from differences in species abundance. Here, we investigated beta-diversity patterns in tropical fish communities of central India and their relation to habitat structural properties and water conditions. We performed our analysis for the overall region (18 sites) and also across three distinct flow conditions (6 sites for each flow regime). We used a partitioning framework to uncover the contribution of abundance replacement and abundance difference to beta-diversity patterns for the overall region and for three flow conditions separately. Our results suggest that at a regional scale all the sites show an equal contribution of replacement and abundance difference components, while seasonal samples were homogeneous. Our results confirmed that intermittent and regulated sites are more heterogeneous than perennial sites. The observed changes in beta-diversity in intermittent and regulated sites were related to both abundance difference and replacement components. Dissimilarities between sites were explained by physicochemical (temperature, pH, dissolved oxygen) parameters but not by habitat structural (stream width, depth) parameters.