Abstract: By the methods of coefficient of difference, variance analysis, discriminant analysis, and principal component analysis (PCA), this paper studied the morphometrics differences, including 10 countable characteristics and 31 proportional characteristics, between the 142 and 92 specimens of endangered species Onychostoma rara collected from the Yuanjiang River and Xijiang River systems, respectively. The variance analysis showed that a total of 6 countable characteristics and 27 proportional characteristics had significant differences between the populations of O. rara from the Yuanjiang River and the Xijiang River systems, respectively (P<0.05). The discriminant analysis revealed that there were 9 proportional characteristics being important to differentiate the two populations from each other, and the discriminant functions for the two populations were established, respectively. Based on the results of PCA, there were 16 proportional characteristics along the dorsalventral axis, 6 proportional characteristics along the anteriorposterior axis, and 2 proportional characteristics along the caudal peduncle of fish body among the individuals of O. rara presenting obvious differences. As a result, the morphometrics of the two populations had shown obvious differentiation, probably due to the longterm segregation of the two populations and their adaptive evolution in different river systems. However, the coefficient of difference demonstrated that the morphometrics differences between the two populations were still under subspecies level.

Key words: forest gap, P. massoniana plantation, soil aggregates, organic carbon, labile organic carbon.