Patterns of larval movement and the spatial scale of dispersal are expected to be major forces in regulating the dynamics of populations and communities in marine systems. The life history of most marine species includes a larval stage that is capable of dispersal over broad geographic areas and efforts to understand the population dynamics of these species have been stymied by the magnitude of larval dispersal inherent in planktotrophic development. The scale of larval dispersal is a key parameter in understanding the recruitment dynamics of marine species. We will exploit the genetic mosaics formed in a hybrid zone between two species of mussels to assess the geographic scale of larval dispersal. In this system, large numbers of larvae are produced at specific locations with distinct genetic signatures and released into the plankton. By monitoring the settlement of these `marked` larvae we will assess the geographic scale and dynamics of larval dispersal. In this study we will capitalize on molecular genetic markers, that we have developed with previous support from Biological Oceanography, that allow the population genetics of mussel larvae or spat to be determined. By exploiting both the molecular genetic markers we have developed, and the presence of genetic mosaics formed by hybridization between mussel species it will be possible to monitor the movement of larvae between geographic areas. Using this system we will determine the geographic scale of larval dispersal, spatial and temporal variation in dispersal capacity and test the hypothesis that patterns of larval movement are predominantly controlled by local circulation dynamics.
