Abstract: The tobacco aphid, Myzus persicae (Hemiptera: Aphididae), is an important pest on cultivated crops worldwide. In order to evaluate the morphological variations of M. persicae populations from eighteen geographical areas in China, such morphological characters as body length, body width and femur length, and Q value of M. persicae were measured and analyzed using ANOVA and Mantel test based on the relationship between the Euclidean distance and the geographical distance or altitude. The ratios of every morphological character to body length were used to carry out hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results showed that there were significant differences in morphometrics among certain geographical populations. The results of HCA and PCA indicated that among the 18 geographical populations, the biggest difference existed between the population from Zhenfeng of Guizhou province and other populations, while the least differences were observed among the populations from Nanniwan of Shaanxi province, Cili of Hunan province, Qiaocheng of Anhui province and Wulong of Chongqing city; the differences among the other populations were between the both. The Mantel Test revealed that there was no significant correlation between the Euclidean distance and the geographical distance or altitude. The morphological differentiation of M. persicae is not in conformity with the geographical isolation mode. Geographical and climatic conditions have influences on the morphological variations of M. persicae populations, which are caused by many factors. The specific mechanisms of morphological differentiation, however, are not clear.

Key words: Myzus persicae, cluster analysis, principal component analysis, morphometry, Euclidean distance, geographical distance