Genetic Analysis Of Parargyrops Edita Population Decline In Beibu Gulf

Parargyrops edita is the main fishing object of bottom trawl and the major component of fishing catch in Beibu Gulf. In recent years, P. edita population in Beibu Gulf showedsome characteristics of recession, such as miniaturization and sexual precocity.However, theresource density of P. edita maintained at a very high level in Beibu Gulf.Traditional fisheries biology study cannot explain perfectly the inconsistent phenomenon. Therefore,the recession situation of the P. editapopulationin Beibu Gulf is difficult to be identified.Using the theory and methods of conservation genetics can help us with a better understandingof the recession situation of the P. edita population. Therefore, in this study, we take P. edita in Beibu Gulf as the object of the reserach. First, we develop microsatellite markers for P. edita using the high-throughput sequencing and polyacrylamide gel electrophoresis(PAGE). Using the obtained microsatellite markers,we analyzed population genetic diversity among 5 different geographical populations of P. edita collectted from Beibu Gulf.Population genetic structure of P. editawas identified using the population genetic diversity data.Subsequently,the effective population size, inbreeding coefficientand genetic bottleneck were calculated respectively to determine the recession situation of the P. edita population.The results of the study are shown as follows:1. Developing microsatellite markers for P. editaP. edita genomic DNA was sequenced usinghigh-throughput sequencingtechnology.2.80 Gbp raw sequence data, 0.12 Gbpspliced sequences of P. editawere detected.292 microsatellite sequences with suitable flanking regions were searched from the spliced sequences.Subsequently,50 pairs of PCR primers are designed and screened using 5 P. Edita individues. As a result, 22 microsatellite markers passed the screening and been evaluate in a wild P. Editapolulation. The number of alleles per locus varied from 2 to 16,and the average is 6.18.The observed heterozygosities ranged from 0.245 to 0.979 and the expected heterozygosities from 0.226 to 0.914 respectively, with means of 0.555 and 0.617,respectively.Four loci deviated significantly from Hardy-Weinberg equilibrium after Bonferroni correction(adjusted P value ≤ 0.0023). No significant linkage disequilibrium was detected among these loci.2. Population genetic diversity of P. edita in Beibu GulfWe analyzed population genetic diversity among 5 geographical populations of P. edita collecting from Beibu Gulfusing 8 optimalmicrosatellite markers. The result shows, the average of alleles,observed and expected heterozygosities are66.8, 0.696 and 0.773 respectively. A total of 80 alleles were detected in 5 geographical populations of P. edita. The average number of alleles in all samples is 10.00, ranging from 3 to 15. The number of alleles per populations varied from 63 to 69. The average of observed and expected heterozygosities for all―population : marker‖ groups varied from 0.333 to 1.000 and 0.574 to 0.918,respectively. The average of observed heterozygosities per sample ranging from 0.677 to 0.709,while,the average of expected heterozygosities per sample ranging from 0.757 to 0.784. In all 40 ―population : marker‖ groups, 4 loci devicated significantly from Hardy-Weinberg equilibrium after Bonferroni‘s correction(adjusted P value ≤ 0.00625).3.Population genetic structure of P. edita in Beibu GulfPairwise FST values were generally low, no exceeding 0.045. All of the pairwise FST values were negative. Those results showed close genetic relationships among the geographical populations.The individual allocation analysis demonstrated that each individual was assigned to each of the 2 or 3 populations(where K was set to 2 and 3 respectively) in approximately equal proportions. While from the individual distribution in the table, individuals from each population can be assigned to each assumed populations with an almost the same proportion. Individualsfrom five populations can be classified together, in other words, all individuals can be merged into one group. Individuals from all sampling regions were therefore pooled for subsequent analysis.4.The decline state of P. edita population in Beibu GulfThe estimates of effective population size of P. edita population in Beibu Gulf ranged from 550 to 650. IR was close to zero among most individuals. No evidence of intrapopulation heterozygote deficit due to contemporary inbreeding(IR =-0.02,FIS =-0.011) was found. The results of genetics bottleneck examination indicated that there was no genetic bottleneck in P. edita population in Beibu Gulf.These results indicate that there are abundant genetic diversities inthe P. edita population, and no evidence of population genetic decline is detected in the population.The results wouldprovide important scientific basisfor management and protection of the P. edita resources.