青岛近岸金乌贼繁殖群体形态特征及遗传分化

为探究青岛近岸金乌贼(Sepia esculenta)繁殖群体结构及其结群历时长、产卵期内亲体规格递减的结群现象,运用形态学度量方法结合微卫星分子标记技术,对青岛薛家岛近岸前、中、后3个不同洄游时期金乌贼繁殖群体的形态特征和遗传分化水平进行统计分析,探究其亲缘关系并量化差异水平。主要结果如下:形态学主成分分析(PCA)结果显示,前3个主成分的累积贡献率为60.067%,低于85%;判别分析(D_A)结果显示, 3个时期繁殖群体的判别准确率介于66.7%～82.1%,两者的散点图结果一致,均显示3个群体未明显占据不相重叠的区域。微卫星标记结果表明, 3个时期繁殖群体的遗传距离D_A介于0.12～0.16,群体遗传分化指数为0.0014～0.0064,利用Structure判断最佳理论组群为1,表明其亲缘关系较近。综合分析认为,虽青岛近海不同洄游时期金乌贼繁殖群体的规格差异较大,但形态学参数差异较小,遗传距离较近且遗传分化水平较低(F_(st)0.05),未呈现明显的群体分化。

Morphological characteristics and genetic differentiation of a breeding population of Sepia esculenta in Qingdao

Population differentiation and structure are important topics of evolutionary biology, and morphology and genetics are the main methods of researching these topics. Sepia esculenta migrates annually from the overwintering field to the spawning ground, and for a long time, it has been thought that the breeding period of its inshore populations was as long as two months. In addition, during the grouping period, the specification of S. esculenta arriving in different stages showed a decreasing trend with arrival time. Thus, the objectives of this study were to characterize the population structure and clustering phenomenon in S. esculenta over time, and discover why the parental specification diminished during spawning of the mature animals in Qingdao. The morphological characteristics and genetic differentiation during three different migratory periods (early, middle, and late) of S. esculenta inhabiting the coastal waters of Xuejia Island were analyzed using morphology and DNA markers. The results showed that the cumulative contribution rate of the first three principal components was 60.067% in the principal component analysis (PCA), which was lower than 85%. The discrimination accuracy ranged from 66.7% to 82.1% in the discriminant analysis (DA). The scatter plots of PCA and DA showed a similar result, which is the species was not clearly dispersed among these three migratory periods. Analysis based on microsatellite markers indicated that genetic distances (D_A) ranged from 0.12 to 0.16 and the genetic differentiation index (F_st) ranged from 0.0014 to 0.0064 in S. esculenta from the three different migratory periods. The optimal number of theoretical groups was 1 according to the genetic structural analysis. These findings suggested that there was no obvious population differentiation among early, middle, and late migratory periods of S. esculenta in Qingdao, owing to the low values of morphological differences, genetic distances, and genetic differentiation, although the population showed a large difference in mantle length and body weight in specifications. The differences in the swimming ability of small and large individuals may be the main reason behind the long period of S. esculenta''s clustering and the decrease of its specification over time. It is undeniable that the differences in morphology and genetics among populations of marine cephalopods populations of fish are unpredictable yet significant. Macroscopic identification methods, such as morphological studies, are vulnerable to the influence of living environment, and at the same time, marine fish with good dispersal ability usually exhibit very low genetic differentiation within a wide geographic range. Therefore, the strong athletic ability of Sepia esculenta may also lead to a similar genetic structure of its populations.