Network topology mediates freshwater fish metacommunity response to loss of connectivity

Abstract

Abstract Changes in connectivity regimes affect patterns of diversity and species richness. In riverine ecosystems, factors that vary through space and time, such as flow, the presence of barriers to movement, and network topology determine connectivity, and in turn shape patterns of diversity and richness. While the effects of network topology and changes in spatiotemporal connectivity regimes on patterns of species richness have been studied in isolation, they have not been studied simultaneously. We used a discrete‐time logistic growth metacommunity model to analyze the role of spatial and temporal functional connectivity in determining patterns of local (patch level) species richness in freshwater fish metacommunities. Our modeling suggests that: (1) the effect of spatial loss of connectivity on local species richness is mediated by network topology and where richness is measured in the system and (2) increasing temporal autocorrelation in connectivity results in increasing temporal autocorrelation in patch occupancy. Spatial and temporal loss of connectivity is a ubiquitous issue for river ecosystems, making understanding and predicting its effects of fundamental importance to both improving theory and guiding river management. Our findings highlight the importance of network topology (and hence context dependency) in shaping metacommunity response to changing connectivity regimes.

Keywords

• dendritic ecological networks
• dispersal
• environmental autocorrelation
• freshwater fish
• spatial connectivity
• temporal connectivity