Disentangling the effects of different human disturbances on multifaceted biodiversity indices in freshwater fish.

Evaluating the effects of anthropogenic pressures on several biodiversity metrics can inform the management and monitoring of biodiversity loss. However, the type of disturbances can lead to different responses in different metrics. In this study, we aimed at disentangling the effects of different types of anthropogenic disturbances on freshwater fish communities. We calculated diversity indices for 1109 stream fish communities across France by computing richness and evenness components for ecological, morphological, and phylogenetic diversity, and used null models to estimate standardized effect sizes. We used generalized linear mixed models to assess the relative effects of environmental and anthropogenic drivers in driving those diversity indices. Our results demonstrated that all diversity indices exhibited significant responses to both climatic conditions and anthropogenic disturbances. While we observed a decrease of ecological and phylogenetic richness with the intensity of disturbance, a weak increase in morphological richness and evenness was apparent. Overall, our results demonstrated the importance of disentangling various types of disturbances when assessing human-induced ecological impacts and highlighted that different facets of diversity are not impacted identically by anthropogenic disturbances in stream fish communities. This calls for further work seeking to integrate biodiversity responses to human disturbances into a multifaceted framework, and could have beneficial implications when planning conservation action in freshwater ecosystems.