Meeting Abstract
The barnacle Semibalanus balanoides and the polychaetes Diopatra neapolitana and Diopatra biscayensis have multiple geographic limits in France, Spain, and Portugal. Population densities near range edges decay exponentially with distance from the population centers in Semibalanus, yet range edges are abrupt in Diopatra. The difference in geometry of range edges could be the result of differences in planktonic larval duration, or to local hydrodynamic barriers to dispersal. To distinguish between these hypotheses, larval transport was modeled with Lagrangian particle tracking, using velocity fields from ocean models developed by the UK Met Office, IFREMER, US Navy, French Navy, and the Spanish Puertos del Estado. Despite large differences in predictions among the different ocean models, Lagrangian particle tracking predicted that the decline in population density from larval source populations was exponential and the slope of the relationship was proportional to the planktonic larval duration. The abrupt range boundaries in Diopatra do not appear to be related to hydrodynamic barriers, rather they derive from a short larval period (< 6 d), and the gradual Semibalanus range edges are most likely due to a longer planktonic period (>30 d).
