U.S.-Japan Dissertation Enhancement: Speciation with Hybridization: The case of Japanese Hexagrammids

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0123805BernardiThis award supports a one-year collaborative research project between Professor Giacomo Bernardi and Karen Crow at the University of California, Santa Cruz and Professor Hiroyuki Munehara of Hokkaido University in Japan as well as Professor Andrey Balanov of the Russian Academy of Sciences in Vladivostok. The researchers will undertake a study of the involvement of speciation with hybridization of the Japanese Hexagrammids. Reinforcement is the build up of assortative mating resulting from natural selection against hybrids upon secondary contact of allopatric species. It has been theorized that reinforcement could be an important force driving speciation. Evidence for reinforcement in laboratory experiments has been difficult to generate, and studies in natural settings have been lacking, especially in marine systems. However, theoretical and empirical support has grown in the last five years and additional studies need to be done to further test these predictions. Fishes of the genus Hexagrammos meet criteria theorized to favor speciation by reinforcement. The research will involve testing whether assortative mating is being built up in conjunction with reduced fitness of hybrids to determine if reinforcement is an important force maintaining species boundaries in this system. The main focus of the proposed research is to determine the role of hybridization in processes of speciation within the genus Hexagrammos. The specific goals are to: 1) characterize the relative proportions of hybrids occurring in nature at three sites in the Northern Sea of Japan; 2) measure post-zygotic reproductive isolation between parental species by estimating differential costs in fitness associated with larvae produced from hybrid, specific and F1-hybrid backcrosses; and 3) estimate pre-zygotic reproductive isolation by comparing differences in assortative mate selection in parental species from both sympatric and allopatric populations.The project brings together the efforts of three international laboratories that have complementary expertise and research capabilities. The process of reinforcement of premating isolation is of great interest in evolutionary biology. Results of this research are likely to provide a major contribution to our understanding of speciation processes, particularly in the area of reinforcement as a mechanism for speciation. The project advances international human resources through the participation of a graduate student. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. The researchers plan to publish results of the research in scientific journals and report on the findings at scientific meetings.