Measuring Connections in the Sea: Pushing the Boundaries of Seascape Genetics at Channel Islands National Park

The challenge of analyzing dispersal in the seascape The exchange of individuals among populations through dispersal, or population connectivity, can profoundly influence the abundance and persistence of local populations (Simberloff and Wilson 1969). Population connectivity is influenced by environmental factors such as mountains, rivers, and habitat corridors that mediate the movement of organisms and the probability of their successful dispersal from one location to another. Understanding population connectivity and the role of environmental factors is critical for effective wildlife conservation and management. Monitoring and mark–recapture experiments have confirmed our intuition and improved our understanding of how landscape features affect the movement of individuals and the probabilities of dispersal between populations for terrestrial species (Wiens 2001). In marine systems, it is more difficult to directly monitor the exchange of individuals among populations. Marine fish and invertebrates are especially problematic due to their production of microscopic larvae that disperse with ocean currents for days to months before settling onto reefs or other habitat and growing into adults. Challenges to estimating population connectivity in marine systems are further exacerbated by our limited knowledge about how the marine seascape influences dispersal.Ocean currents have complex patterns and features that disperse marine larvae,much like wind and weather patterns disperse airborne seeds on land, but there is far less continuous monitoring and documentation of these patterns in the ocean. Because of the difficulty of tracking marine larvae, and our limited understanding of the environmental factors influencing dispersal in the sea, the question of where larvae disperse, and consequently, the degree of connectivity among populations, remains largely unanswered (Cowen et al. 2000). This creates a significant challenge for the management of nearly every marine species. Many marine ecologists have turned to population genetics as a tool for indirectly estimating population connectivity. Unfortunately, the complex genetic patterns among popula-