Network theory and metapopulation persistence: incorporating node self‐connections

Abstract

Network analysis is gaining increasing importance in conservation planning. However, which network metrics are the best predictors of metapopulation persistence is still unresolved. Here, we identify a critical limitation of graph theory-derived network metrics that have been proposed for this purpose: their omission of node self-connections. We resolve this by presenting modifications of existing network metrics, and developing entirely new metrics, that account for node self-connections. Then, we illustrate the performance of these new and modified metrics with an age-structured metapopulation model for a real-world marine reserve network case study, and we evaluate the robustness of our findings by systematically varying particular features of that network. Our new and modified metrics predict metapopulation persistence much better than existing metrics do, even when self-connections are weak. Existing metrics become good predictors of persistence only when self-connections are entirely absent, an unrealistic scenario in the overwhelming majority of metapopulation applications. Our study provides a set of novel tools that can substantially enhance the extent to which network metrics can be employed to understand, and manage for, metapopulation persistence.

Designing connected marine reserves in the face of global warming

“…While the protection of hubs and stepping stones significantly improved overall connectivity (including under future warmer conditions), adding the protection of self‐sustaining populations could be necessary in some cases (Magris et al., ; White et al., ). While we did not target high self‐recruitment areas, our analysis indicated that these areas were incidentally included in solutions (e.g., within modeling units 1, 8, 11; Figure ), yet we suggest SCP applications should consider identifying and explicitly targeting self‐recruitment areas (Zamborain‐Mason, Russ, Abesamis, Bucol, & Connolly, ). Furthermore, assigning higher objectives to upstream sites showing high centrality makes sense from a metapopulation point of view, yet the relation of centrality with genetic diversity is inverse in the RGI, at least for some species (Lodeiros et al., ).…”

Node self‐connections in network metrics

“…Zamborain‐Mason et al . () state that they have identified a critical limitation of existing network metrics for predicting metapopulation persistence, which consists in their omission of node self‐connections, and that they have newly proposed metrics that account for node self‐connections.…”

The relative importance of local and regional processes to metapopulation dynamics

“…Metapopulation ecology shares numerous conceptual and analytical commonalities with landscape ecology (DiLeo, Husby, & Saastamoinen, ; Howell, Muths, Hossack, Sigafus, & Chandler, ) and network ecology (Box 1 and Urban & Keitt, ; Urban et al, ). Bridging these disciplines can provide conceptual synthesis and lead to a better understanding of patch occupancy patterns (Gilarranz & Bascompte, ; Rozenfeld et al, ; Urban & Keitt, ; Zamborain‐Mason, Russ, Abesamis, Bucol, & Connolly, ). We find that local‐scale habitat variables are equally capable of predicting metapopulation dynamics as regional‐scale measures of connectivity, but that the best performing models included both local‐ and regional‐scale variables together.…”