The Genetic Structure And Introgression In Hybrid Zones Of Bostrychus Sinensis In Fujian And Zhejiang Coastal Areas

The Chinese four-eyed sleeper(Bostrychus sinensis)is a species of fish in China belonging to Vertebrata,Actinopterygii,Perciformes,Eleotridae,Bostrychus.In this study,three molecular markers(microsatellite markers(SSR),mitochondrial DNA(mtDNA)gene sequences and nuclear gene RyR3 sequences)were used to detect and analyze the genetic structure and introgression of hybrid zones with a total of 534 samples in six populations along Fujian and Zhejiang coastal areas.The factors that promote the formation and maintenance of hybrid zones are various,depending on the origin of the hybrids,the composition of the hybrid zones and their adaptability.Therefore,it is important to study the genetic structure and infiltration of the population in the hybrid zone to understand the adaptability The conclusions are as follows:1.In the microsatellite data(SSR)analysis,15 highly polymorphic microsatellite loci were selected,the number of alleles per locus was 7?44,the range of observed heterozygosity(Ho)was 0.1546-0.9600,and the range of expected heterozygosity(HE)ranged from 0.4357 to 0.9602,the polymorphic information content(PIC)of each microsatellite locus was 0.2780?0.9523.indicating that the population of Chinese four-eyed sleeper population was highly polymorphic.The inbreed coefficient(Fis)is-0.3136?0.4487.The Fis of most seats is positive,which indicate that the heterozygous deletion occurred in the population.2.In this study,the length of Cytb gene was 1141 bp,and 122 variable sites were detected.Among them,there were 79 parsimony informative sites,and 122 haplotypes were defined.The haplotype diversity of 6 geographical populations was between 0.765 and 0.895,and the nucleotide diversity(?)appeared between 0.00157 and 0.002102.The situation included high haplotype diversity(Hd)and low nucleotide diversity(?).The genetic diversity of Yuhuan was the highest among the six geographical populations,and Xiamen was the lowest at the same time.In the nuclear gene(RyR3)analysis,there were 28 variable sites in the sequence with length of 820 bp,among which had 26 parsimony informative sites.The haplotype diversity was between 0.612 and 0.799.And the nucleotide diversity was between 0.00330 and 0.00612.which was consistent with the results of Cytb gene sequence analysis.3.The NJ tree and Structure clustering analysis based on the genetic distance matrix among the populations showed that the Chinese four-eyed sleeper could be divided into two groups,and the genetic distance had a significant correlation with the geographical distance.(P<0.05).The gene flow(Nm)between adjacent populations was large and the frequency was frequent,while the gene flow between the north and south groups was small,which may be related to the geographical isolation factors and the special biological characteristics of Chinese four-eyed sleeper.4.The haplotype network structure based on the Cytb gene sequence and RyR3 showed that the populations of the Chinese four-eyed sleeper were significantly divided into two groups.Tajima'D(D),Fu'Fs(Fs)test and nucleotide mismatch distribution test also indicated that,in addition to the recent population expansion in Xiamen,there was no expansion occurred in other populations.5.The five geographical samples of the northern part of the Taiwan Strait(Xiapu to Zhoushan)were composed of N-lineage,S-lineage and hybrid population,which confirmed that the East China Sea area was the secondary contact area of the Chinese four-eyed sleeper.The adaptability of the hybrid was relatively low to that of the parental species,and the hybrid zones were restricted to the two parental species.The narrow area is mainly maintained by the balance between the diffusion and selection of the hybrids.In the hybrid zone,the loss of alleles resulted in the decrease of the viability of the hybrids.When the spawning season was in the summer,the population of the Chinese four-eyed sleeper was spread from the south to the north in the second contact area,and the allele deletion was balanced.On the whole,the two clades are in the early stages of the species formation process.