Population Genetic Structure And Divergence Of Spotted And Japanese Sea Bass Inhabiting Chinese And Japanese Coasts

Molecular ecology is a new branch of modern ecology, combines ecological and population biology theories with modern molecular biology techniques. In all technology used in molecular ecology researches, SSR markers are one of the most suitable and efficient tools for researches of marine fishes. Although recent papers report behaviors of SSR loci violated ideal marker properties, a set of SSR loci passed rigorous screening protocols for given samples will perform well in population parameter estimating.Spotted sea bass (Lateolabrax maculatus) , which inhabits East Asia coasts and cage-cultured as well in China currently, needs scientific management for sustainable exploration urgently. A set of SSR marker will certainly facilitate the management and exploitation of the genetic resource of L. maculatus. 22 microsatellite DNA markers are developed and used to type 35 individuals collected along the Chinese coast. The number of alleles per locus range from 3 to 23. The expected heterozygosities range from 0.111 to 0.938. The observed heterozygosities range from 0.114 to 0.914. All 22 loci are neutral and independent each other, of them, 2 deviate significantly from Hardy-Weinberg equilibrium. These microsatellite DNA markers are moderately informative. For the low ratio of positive clone in FIASCO used in spotted sea bass SSR isolation, a more stringent heating elution protocol is added after the alkaline elution. The fragments eluted produce more positive clones than original protocols significantly (P=0.0003) . In addition, a more convenient method named DSPT are used and modified. To selecting fragments with more than 5 inner repeats of combined SSR, EcoR I adapter primer combined with (TC)₆ (AC )₅ (system A ) and (AC)₁₂B (system C ) are used in two different RCR screening systems for the same clone. The group of SSR loci with more than 5 inner repeats has significantly differences in signal deference A-C with Loci group with inner repeats less than 5 repeats (P=0.0036) . The different between A and C signals can be criterion for suitable combined SSR loci selection.Of 22 microsatellite DNA markers developed from spotted sea bass (L. maculatus) , 19 are independent from each other and at Hardy-Weinberg equilibrium across the 3 populations of spotted sea bass inhabiting Chinese coasts and the five populations of Japanese sea bass (L. japonicus) inhabiting Japanese coasts. These 19 markers are used to determine the number of alleles and the expected heterozygosity across the eight populations. The majority of individuals (93.8-98.8%) of the three populations of spotted sea bass are assigned to an inferred cluster, and 90.9-94.6% of the individuals of the five populations of Japanese sea bass are assigned to the other. The average number of alleles across the 19 loci is significantly lower in spotted sea bass than in Japanese sea bass (10.3 vs 15.4) , however, the average expected heterozygosity across 19 loci of spotted sea bass is similar to that of Japanese sea bass populations (0.743 vs 0.750). An effective population size reduction (i.e. bottleneck effect) is detected in spotted sea bass (P = 0.00357), which may have resulted from either over-catching or glaciations or both. The pair-wise F_ST among populations of spotted sea bass (0.019-0.029) and among populations of Japanese sea bass(0.003-0.021) are lower than those between the populations of spotted and Japanese sea bass (0.076-0.101) . The average pair-wise F_ST between populations of spotted and Japanese sea bass reaches 0.075 and the variation between spotted and Japanese sea bass accounts for 7.16% of the total. Nei's original measures of genetic distances among populations of spotted and Japanese sea bass range from 0.123 to 0.145 and from 0.055 to 0.123, respectively, while that between the populations of spotted and Japanese sea bass group range from 0.326 to 0.450. Both species are able to disperse over a long distance; however, our observations demonstrate that they cannot migrate across a possible barrier existing between Chinese and Japanese coasts. Most individuals of Zhoushan population of spotted sea bass are assigned to two inferred clusters, indicating that Zhoushan is gathering ground of spotted sea bass. Most individuals of Ariake Sea, Tokyo Bay and Ishikawa populations of Japanese sea bass are assigned to three inferred clusters, indicating that these locations are gathering grounds of Japanese sea bass. The genetic structure of spotted sea bass (L. maculatus) inhabiting Chinese coast is determined with 23 microsatellite DNA markers. The Nei's expected heterozygosities of Beihai, Weihai and Zhoushan geographic populations (Group A) are similar each other. These 3 populations differentiate slightly; however, the individuals collected around year 2000 belonged to a single panmictic group. The bottleneck event is detected in Group A as a whole and in Weihai and Beihai geographic populations. Two Yantai populations (Group B) are genetically identical; Both Nei's expected heterozygosities and mean numbers of alleles of them are similar. The individuals of Group B and those of Weihai geographic population belong to a single panmictic group, indicating that the genetic structure of the spotted sea bass along the coast of Shandong Peninsula is unchanged from 2000 to 2006.The conducted population structure researches can not answer questions of sympatric distribution of spotted and Japanese sea bass in southern Korean peninsula. A lot of species inhabit Northwest Pacific marginal sea areas show profound distribution patterns that can not be clearly understood. To resolve these problems, the history of sea-land changes must be clarified and the special-temporal forming factors of population division must be separated. The direct response to marine environment changes, the resistance to small scale disturbance and inshore and inland water inhabiting behaviors guarantee finless porpoise a suitable model species for historical biogeographical event recording. In all population inhabit Yangtze River and Chinese and Japanese coasts, haplotype C is the most ancient haplotype belongs to ancestor population. NCPA of finless population inhabit Chinese and Japanese coasts reveals that, the ancient population with C haplotype expanded to pacific coasts of Japanese islands, Southern Japanese coasts of post-arc marginal sea and Yangtze River and divided in different populations with new haplotypes. Populations inhabiting Ariake Sound-Tachibana Bay and Yellow Sea isolated from others according to NCPA results, which explained the high nucleotide and haplotype diversities detect in these populations. But the deviation factors of these two from ancient population cannot be deduced in this study. This study alone cannot clarify the factors forming current distribution patterns of spotted and Japanese sea bass. But after being integrated with results of future studies, the clarified background of sea-land changes in Northwest Pacific marginal sea will greatly facilitate the interpretation of complicated distribution patterns of species inhabiting these areas.