Abstract

Investigation of intraspecific morphological variation is critical for the understanding of evolutionary and ecological processes, and may provide insights for uncovering the roles of natural selection, gene flow, and genetic drift in the distribution and abundance of species diversity. In the present study, we analyzed statistically the patterns of variation of 13 morphological traits among 12 populations in three localities of an endemic orchid, Changnienia amoena. The results showed that, among the three localities, the mean value of all measured morphological traits is the highest in the Lushan populations. There is abundant variation at both the species and population levels. Coefficient of variation (CV) varied between 0.02 and 0.30 at the species level, and the CV values of reproductive organs were lower than those of vegetative structures. ANOVA analysis showed that there was significant difference in most morphological traits among the three localities. UP-GMA analysis showed that the populations in three localities were clustered into three main clades, the populations from Xinning and Lushan formed one clade, while the Shennongjia populations formed another clade. It is noteworthy that the Shennongjia populations were separated into two subclades corresponding to the populations at Longmenhe and Guanmenshan, respectively. This morphological differentiation is most likely a result of pollinator-mediated selection because this species is pollinated by different bumblebee species at these two sites. Pearson correlation analysis showed that high correlation occurred within the vegetative organs, reproductive organs, and be-tween them. These results have important implications for our understanding of the evolutionary processes and mechanism of C. amoena and might provide useful information for the conservation and management of this endangered orchid.