Population Genetics For Chinese Sillago (Sillago Sinica) And Japanese Sillago (sillago Japonica) Based On Microsatellite Markers

Chinese sillago (Sillago sinica) and Japanese sillago (Sillago japonica), whichbelong to the family Sillaginidae, order Perciforms, are carnivorous species. They aremigratory fishes inhabiting inshore region with great economic value. The Chinesesillago is a newly documented species which has only been found in Laizhou Bay,Qingdao, Wenzhou, Xiamen and Gwangyang Port of Korea so far. The Japanesesillago is mainly distributed in the coastal water of China, Japanese, Korea andPhilippines. In the present study, the microsatellite genomic libraries of Chinesesillago and Japanese sillago were developed by two enrichment methods based onnylon membrane and magnetic beads, respectively. Additionally, we estimated thepopulation genetic diversity and population structure of Chinese sillago and Japanesesillago to infer the relative role of environmental factors and ecology habit in shapingand maintaining the geographical patterns of these two species. The results wouldprovide basic information in formulating exploitation and protection rules of Chinesesillago and Japanese sillago resource.1. Isolation of microsatellite markers and population genetics for Chinesesillago, Sillago sinica.(1) Isolation and characterization of microsatellite markers for S. sinicaThe microsatellite genomic library of S. sinica was developed by the method ofmembrane enrichment.81sequences of totally131ones contained microsatelliterepeats. All the24primer pairs were screened in24samples of S. sinica,8primerpairs were successfully amplified and showed polymorphic. The number of alleles perlocus ranged from2to14, and the observed and expected heterozygosity varied from0.125to0.958and from0.120to0.904, respectively. All the loci conformed to Hardy–Weinberg equilibrium, and null alleles were not detected in these loci.(2) The population genetic diversity and population structure of S. sinicaThe analysis of genetic diversity for S. sinica showed that the mean observed andexpected heterozygosity varied from0.502to0.604and from0.433to0.551,respectively. The polymorphic information content was from0.110to0.779. Inconclusion, the genetic diversity of S. sinica was in medium level compared withother marine fishes. The effective population size of all the four populations of S.sinica was below2000. The smaller effective population size might lead to inbreedand genetic drift, which might further more result in lower genetic diversity. The FSTamong the four populations was from0.069to0.189and the significant populationgenetic structure was detected among S. sinica populations based on the analysis ofSTRUCTURE, AMOVA and3D-FCA. We speculated that ecology habit of S. sinicaand spawning ground destruction may play an important role in shaping populationstructure.2. Isolation of microsatellite markers and population genetics for Japanesesillago, Sillago japonica.(1) Isolation and characterization of microsatellite markers for S. japonica.The microsatellite genomic library of S. japonica was developed by the methodof magnetic beads enrichment,241sequences of totally336ones containedmicrosatellite repeats. All the96primer pairs were screened in24samples of S.japonica,24primer pairs were successfully amplified and showed polymorphic. Thenumber of alleles per locus ranged from7to24, and the observed and expectedheterozygosity varied from0.333to0.913and from0.744to0.963, respectively.Significant deviation from Hardy–Weinberg equilibrium was detected at eight lociand no linkage disequilibrium was detected between pairs of loci. Six of these locishowed evidence of null alleles.(2) The population genetic diversity and population structure of S. japonica. The analysis of genetic diversity for S. japonica based on seven polymorphicmicrosatellite loci showed that149alleles were detected and the mean observed andexpected heterozygosity varied from0.643to0.773and from0.678to0.880,respectively. Apart from two loci in Beibu Bay population showed lower polymorphicinformation content, the value in other loci and populations was from0.589to0.921.The relatively high genetic diversity for S. japonica was due to large effectivepopulation size of this species. High significant genetic differentiation was foundbetween Beibu Bay population and other seven populations. All the analysis ofSTRUCTURE, AMOVA and3D-FCA supported the above view. Mantel test andregression analysis confirmed that genetic differentiation is positively correlated withthe geographic distance. The geographic distance, ecology habit, as well as the specialocean current of Qiongzhou strait bring about the limited gene flow of S. japonica...