The dispersal of individuals among marine populations is important to metapopulation dynamics, population persistence, species expansion, and the flow of genetic information. Understanding this connectivity between distant populations is key to their effective conservation and management. For many marine species, population connectivity is determined largely by ocean currents transporting larvae between distant patches of suitable habitat. Recent work has focused on the biophysics of marine larval dispersal and its importance to population dynamics at multiple scales, although few studies have evaluated the spatial and temporal patterns of this potential dispersal. Here, I show how an Eulerian advection-diffusion approach can be used to model the dispersal of larvae between reefs throughout the Tropical Pacific. I illustrate 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. Patterns in the dispersal graphs highlight potential pathways for larval dispersal throughout the Tropical Pacific. Network analysis identified critical island ‘stepping stones’ and highly connected island clusters. Intersecting the dispersal graphs with geopolitical boundaries, anthropogenic threats, current marine protection efforts, and future climate predictions, suggest areas that should be prioritized for marine conservation efforts. The cross-scale analysis of local-scale connectivity, focusing on the island of Tutuila, American Samoa, demonstrates the applicability of this graph-theoretic approach to investigating spatial patterns in coral community structure and informing the local marine management 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 explain and explore the geographic structure in the genetic differentiation of marine species. Collectively, the Pacific-wide and local-scale 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 process.

For more information, please see http://www.duke.edu/~eat4/ or contact me at etreml at gmail.com.