Abstract

The concept of connectivity is central to the study of marine population dynamics, marine biodiversity, and the conservation of marine species. To better understand the scale and spatial patterns in marine population connectivity, we constructed marine dispersal networks using a spatially explicit biophysical model to simulate coral dispersal between reefs. Although this approach is illustrated for the Tropical Pacific, the methodology is applicable to the Caribbean and other locations and spatial scales. The model of coral dispersal incorporates realistic surface current velocity data, habitat configuration, pelagic larval duration, mortality, and settlement probability estimates. We illustrated how this connectivity can be analyzed using graph theory – an effective approach for exploring patterns in spatial connections, as well as for determining the importance of each site and pathway to local and regional connectivity. Results indicate that the scale of dispersal in the Pacific is on the order of 50 – 200 km, varying geographically and among seasons and years. Network analysis identified critical island ‘stepping stones’, persistent dispersal barriers, and highly connected island clusters. Intersecting the dispersal graphs with geopolitical boundaries, anthropogenic threats, and current marine protection efforts, suggest areas that should be prioritized for marine conservation efforts. Finally, the larval dispersal predictions (dispersal networks) were used to test the isolation-by-distance hypothesis of genetic differentiation for three marine species. The strong correlation between the dispersal network predictions (graph distance) and genetic distance across species illustrates the potential for using these methods to explore the geographic structure in the genetic differentiation of marine species. Collectively, the hydrodynamic modeling, graph-theoretic approach, and spatial analysis, provide a robust examination of coral reef connectivity and a framework for integrating results into the marine conservation and management process

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