MARINE BIOTECHNOLOGY FELLOWSHIP: Biological Invasion and Genetic Intorgression of Exotic Mussels -- A Molecular Approach

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Marine biological invasions are pervasive, and an understanding of the processes and mechanisms of invasions is important to our ability to manage and conserve marine resources. Biological invasions are also large.scale experiments in ecology and evolution, providing unique opportunities to study basic ecological and genetic processes in the world' oceans, including dispersal, recruitment, gene flow, and hybridization. This project will examine the temporal and spatial pattern of spread of an introduced mussel, and the extent of genetic introgression into populations of native mussels. This research will exploit the on.going incidental release of genetically distinct larvae of the exotic mussel, >Mytilus> >galloprovincialis>, to study the invasion of a species with pelagic larvae. >M.> >galloprovincialis> larvae are released into San Francisco Bay on a daily basis in the ballast water of Japanese ships. Our studies have shown that 4 x 10.6 mussel larvae may be released from a single ship. Because San Francisco is the only port in cent>>>>ral California large enough to receive ocean.going ships, all central California populations of >Mytilus> >galloprovincialis> likely stem from introduced population in San Francisco Bay. The PI will develop a set of primers (for mitochondrial and nuclear ribosomal genes) for the polymerase chain reaction (PCR) specific to invading Japanese >M.> >galloprovincialis> and to native >Mytilus> spp. Using PCR as an assay, the PI will then establish the distribution of Japanese >M.> >galloprovincialis> genotypes inside San Francisco Bay and in outlying bays and estuaries. This will elucidate intraregional patterns of dispersal of an invading species with pelagic larvae. Further, because nuclear genotypes have 2 sets of chromosomes, assay by PCR will detect hybrid genotypes, revealing genetic introgression into native populations. Combining mtDNA and nDNA analyses will allow detection of asymmetrical introgression. Until recently, the history of invasion by an exotic species could only be inferred from present day distribution, and little inferred about the >rate> of invasion. However, because PCR allows the amplification of DNA from preserved material, mussels collected (and preserved in museum collections) throughout the period of invasion on the North American west coast can analyzed using the primers developed in this project. In this way, it will be possible to reconstruct both the pattern and rate of invasion by >M.> >galloprovincialis>. This study, the first to apply molecular techniques to an ongoing marine invasion, will provide new insights in the processes of dispersal and introgression of alien genotypes during a biological invasion.