Dispersal is a major life history characteristic composed of many interacting traits. Most arguments about the evolution of dispersal patterns assume that there is significant genetic variation for these traits and that they covary genetically with other traits influenced by natural selection. A major difficulty in understanding the evolution of dispersal patterns has been the inability to quantify individual differences in those biological parameters contributing to dispersal potential. In the marine slipper snail, Crepidula fornicata, the principal biological trait governing dispersal capacity is the duration of a free-swimming larval stage. Larval of Crepidula must develop in the plankton for one to several weeks before becoming capable of metamorphosing to the sedentary juvenile stage. This period of obligatory dispersal can now be quantified for individual larvae. The study will determine the quantitative genetic covariance with other larval and post-metamorphic traits that have been previously proposed to influence the development of metamorphic competence and fitness variation, and will specifically test the hypothesis that dispersal capacity may evolve through its genetic correlation with other traits that are subject to natural selection. The study will contribute to the increased understanding of the biology of marine shellfish populations, and populations of other intertidal and estuarine species.
