Connectivity indices can predict population persistence in river networks: insights from a metapopulation model

TL;DR

This paper shows that connectivity indices like DCI can predict how well fish populations persist in river networks, helping guide conservation efforts.

Contribution

The study demonstrates that the Dendritic Connectivity Index reliably predicts population persistence across different river network structures and dispersal scenarios.

Findings

DCI strongly correlates with population persistence at both network and reach scales in dendritic river systems.

DCI–persistence correlations vary with dispersal ability and scale, being strongest under global dispersal at the network scale.

Improvements in DCI after simulated barrier removal correlate with increased population persistence.

Abstract

Connectivity across river networks facilitates species movement and ecological processes that contribute to freshwater biodiversity. Certain indices provide measures of connectivity to focus conservation planning.

Our objective was to test whether commonly used connectivity indicators based on network structure can reliably predict population persistence.

We used a spatially explicit metapopulation model for freshwater fish that complete their life cycle entirely within river networks and depend on connectivity for movement. Simulations were conducted across a range of network sizes, topologies, dispersal abilities, and barrier passabilities. We assessed the relationship between the Dendritic Connectivity Index (DCI) and metrics of persistence at the network and the reach scale.

DCI was strongly correlated with persistence at both the network and reach scale across most simulated network sizes and configurations, particularly in dendritic (branching) systems with symmetric barrier passability. At the network scale, correlations were strongest with density-independent persistence metrics, which is expected since DCI does not incorporate population interactions. Species dispersal ability influenced DCI–persistence correlations differently across scales: correlations were strongest at the network scale when dispersal distances spanned the full network (global dispersal) and at the reach scale when movement was limited to neighbouring segments (local dispersal). We also found that increases in DCI following simulated barrier removal were associated with improvements in persistence, further demonstrating its potential to support restoration efforts.

Indicators like DCI can inform connectivity-focused conservation planning in river networks.

The online version contains supplementary material available at 10.1007/s10980-025-02278-8.

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