Exploring the spatio-temporal dynamics of disturbed metacommunities: A mechanistic modeling approach to species resistance and resilience strategies in drying river networks

Abstract

Understanding how natural disturbance regimes drive biodiversity is a major research challenge. Yet, how species’ ecological strategies and disturbance regimes shape the structure of metacommunities across space and time remains poorly understood. In drying river networks (DRNs), drying events disrupt both local habitat within reach and connectivity among flowing sections. Drying-rewetting cycles alter two major mechanisms: ecological drift and dispersal dynamics. In this study, we present a mechanistic metacommunity model that simulates species’ ability to withstand drying (resistance strategy) and to recolonize communities after rewetting (resilience strategy characterised by species’ dispersal rate and dispersal distance). Coupling this model with realistic hydrological models, we simulated community dynamics in four European DRNs encompassing variable flow intermittence regimes. We investigate the relative importance of flow intermittence, network connectivity and species’ ecological strategies in shaping spatio-temporal meta-community patterns. We show that higher connectivity increases reach-level α-diversity and decreases reach-level temporal β-diversity, whereas flow intermittence has the opposite effects. At the metacommunity scale, more intermittent DRNs exhibited low mean α-diversity and high spatial β-diversity, while DRNs with downstream drying exhibited high temporal β-diversity. Finally, we show that high levels of species drying resistance and dispersal counteract the effect of flow intermittence, leading to high mean α-diversity and low spatial and temporal β-diversities at the metacommunity scale. In contrast, dispersal distance had complex, non-linear effects on spatial and temporal β-diversities, because dispersal amplifies both community stochasticity and biotic homogenisation. Our work emphasises how stochastic recolonisation of disturbed communities and biotic homogenisation interact with species resilience and resistance strategies to shape the spatio-temporal structure of biodiversity