In order to understand the role of recruitment in the population dynamics of marine species which have high larval dispersal it is necessary to understand the movement of the larvae, their geographic origin and the forces that control their local abundance. Methods for tracking larval movements have been restricted to short time scales or within closed systems but their application to high dispersal systems has been of limited value because of the difficulties with larval recovery. The mussel Mytilus edulis consists of a complex of sibling species that hybridize in discrete areas of contact between the parental forms. Individual mussel larvae can be genetically identified as having originated from either of the parental population, or from populations that contain hybrids. Hybrid larvae can only have originated from populations that contained both parent taxa or F1 hybrids. Using this system it will be possible to obtain information on the origin of larvae at several geographic scales. New techniques are required to genetically identify individual larvae. The methods which will be developed in this research program will allow individual larvae to be assayed directly, with minimal preparation and a high rate of processing. Once the techniques have been developed it will be possible to identify the geographic origin of dispersing or recruited larvae. Once developed this new technique will be employed to study larval dispersal in regions of contact between Mytilus populations.
