Morphological variation analysis on redbelly tilapia (Coptodon zillii) of Hongshui River in Guangxi.
Objective: According to the morphological difference analysis on invasive redbelly tilapia (Coptodon zillii) from seven geographical populations (Tian'e, Donglan, Bama, Dahua, Du'an, Heshan and Laibin) in the Hongshui River drainage basin of Guangxi, the ecological variation and living condition under different geographical habitats were explored, and the invasive status and hazard risk of this species were scientifically assessed. Method: Traditional morphological and framework measurement data of 865 wild male C. zillii collected from above seven populations were analyzed by principal component analysis, discriminant analysis and cluster analysis. Result: Principal component analysis extracted a total of six principal components (PCA1-PCA6). The first three principal component factors had high contribution rate, and mainly reflected morphologic changes on the head-to-tail axis, trunk and tail of the fish. By making a scatter plot on the scores of PCA1 and PCA2, the morphological separations of most populations were significant, and came mainly from the PCA1. In the discriminant analysis, discriminant accuracy of seven geographical populations was 80.12%-98.52%, and comprehensive discriminant accuracy was up to 91.29%. Apart from the mutual misjudgment of some individuals between Laibin and Bama population, oilier geographic populations could be well distinguished by discriminant functions. Cluster analysis showed that the C. zillii in Laibin and Bama were clustered into a single clade and had the lowest similarity with those from other populations which however had the higher similarity among each other. On the regression analysis and fatness calculation based on the body length and body weight, the wild C. zillii of seven populations grown at a constant speed and with high fatness. Conclusion: The redbelly tilapia (Coptodon zillii) from different geographical populations of the Hongshui River has been produced the obvious adaptive differentiation under good living conditions. It is urgent to take prevention and control measures of C. zillii intrusion.