Pelagic larval duration and dispersal distance revisited

I present dispersal distances for 44 species with data on propagule duration (PD) for 40 of these. Data were combined with those in Shanks et al. (2003; Ecol. Appl. 13: S159-S169), providing information on 67 species. PD and dispersal distance are correlated, but with many exceptions. The distribution of dispersal distances was bimodal. Many species with PDs longer than 1 day dispersed less than 1 km, while others dispersed tens to hundreds of kilometers. Organisms with short dispersal distances were pelagic briefly or remained close to the bottom while pelagic. Null models of passively dispersing propagules adequately predict dispersal distance for organisms with short PDs (<1 day), but overestimate dispersal distances for those with longer PDs. These models predict that propagules are transported tens of kilometers offshore; however, many types remain within the coastal boundary layer where currents are slower and more variable, leading to lower than predicted dispersal. At short PDs, dispersal distances estimated from genetic data are similar to observed. At long PDs, genetic data generally overestimate dispersal distance. This discrepancy is probably due to the effect of rare individuals that disperse long distances, thus smoothing genetic differences between populations. Larval behavior and species' life-history traits can play a critical role in determining dispersal distance.