Environmental drivers of α-diversity patterns in monsoonal tropical stream fish assemblages: a case study from tributaries of Narmada basin, India

Abstract

Environmental factors, such as local physico-chemical water parameters, habitat-structural conditions, geography and human disturbances can have a profound impact on the structure and composition of biotic communities. This study investigates the relationship of these factors with fish diversity in medium to small streams in Central India and identifies the key determinants of species richness and diversity in habitats increasingly facing impacts of urban development. Data on fish diversity on eighteen sites, representative of undisturbed and disturbed aquatic habitats, located in the Narmada river basin were collected across different seasons over two years. Seasonal patterns of alpha diversity for this region were analysed and the effect of environmental drivers on seasonal patterns of alpha diversity were assessed. Analyses of species data revealed significant differences in diversity patterns across seasons for both species richness and Shannon diversity. Results of generalized linear mixed models showed that along with disturbance, altitude and substrate heterogeneity, dissolved oxygen, pH and stream width proved to be important environmental variables that predict species richness. Further, variations in pH, dissolved oxygen, temperature, stream width, stream depth and stream width heterogeneity were found to also predict Shannon diversity index. Our study revealed that seasonal changes across the year play a crucial role in shaping diversity patterns. This study is relevant as an important step in identifying roles of various ecological factors driving fish diversity in the region and towards developing long term management plans for critical catchment areas of major rivers in tropical systems.