基于耳石几何形态测量学的长江安徽江段刀鲚群体识别研究

POPULATION IDENTIFICATION FOR COILIA NASUS IN ANHUI SECTION OF THE CHANGJIANG RIVER BASED ON OTOLITH GEOMETRIC MORPHOMETRIC ANALYSIS

  • 摘要: 为了解长江安徽江段刀鲚耳石的形态特征和尝试识别不同群体, 研究选用基于地标点的几何形态测量学手段, 对不同年份采于长江安徽安庆、铜陵江段长颌鲚和短颌鲚2种生态表型的5个群体刀鲚矢耳石形态差异性进行了比较研究。基于12个地标点, 将其坐标进行相对扭曲主成分分析及判别分析, 经薄板样条分析和网格变形, 使其耳石形态变异矢量可视化。结果显示, 在相对扭曲主成分分析中, 提取的地标点中多为Ⅱ类地标点, 其贡献率为69.48%, 说明Ⅱ类地标点是耳石形态差异的主要来源。5个群体刀鲚判别分析的综合判别准确率为95.6%, 表明这些刀鲚群体耳石形态的差异总体显著。这种差异显著性尤其存在于长颌鲚与短颌鲚生态表型间及长颌鲚和短颌鲚不同群体间, 显示出刀鲚不同生态表型分化及其群体间差异性已可体现在耳石的形态特征上。上述发现可为长江十年禁渔前后安徽江段刀鲚群体组成和群体差异性的客观评价提供理论支撑。

     

    Abstract: Estuarine tapertail anchovy Coilia nasus is believed as a “flagship species” “indicator species” and “umbrella species” for protection of the Changjiang River ecological system. In order to reveal the otolith morphological characteristics and population delineation/identification of C. nasus in Anhui section of the Changjiang River, the landmark-based geometric morphometric analysis was utilized to comparatively study the sagittal otoliths of two ecomorphotypes (i.e., the long supermaxilla C. nasus and short supermaxilla C. brachygnathus) and five populations of the anchovy in Anqing and Tongling sections of the Changjiang River in Anhui Province. The left sagittal otolith of each specimen was used in the present study. A Leica M205A stereo microscope was used to photograph the otolith samples. Subsequently, tpsDig2 software was used to establish and measure the landmark points on the otolith photos. Based on 12 landmarks, the coordinates were analyzed by relative distortion component analysis and discriminant analysis. The morphological variation vectors were then visualized through thin plate spline analysis and mesh deformation. The results show that most of the extracted landmarks are type Ⅱ landmarks, and their contribution rate is 69.48% in the analysis of relative distorted main components, indicating that type Ⅱ landmarks were the main source of otolith morphological differences. The general discriminant accuracy of the five populations was 95.6%, indicating that significant differences in otolith morphology were generally existed among the populations of C. nasus. Especially, 100% classification accuracies were achieved for the variation between long supermaxilla C. nasus and short supermaxilla C. brachygnathus, as well as among 3 populations of long supermaxilla C. nasus. Therefore, it will be reasonable to believe that the differences of otolith morphometrics particularly observed in the long vs. short supermaxilla ecomorphotypes and 3 populations of long supermaxilla C. nasus could reflect the evidences of ecomorphotype differentiation and high/low level population connectivity. The aforementioned findings can provide theoretic basis and supports for objective evaluations of resource composition and population difference of C. nasus in Anhui section of the Changjiang River before and after the 10-year fishing ban policy. Furthermore, this study provides an important reference case for population delineation or identification of different ecomorphotype C. nasus in other waters and other commercial fish resources the Changjiang River Basin.

     

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