Abstract
BackgroundTree peonies are great ornamental plants associated with a rich ethnobotanical history in Chinese culture and have recently been used as an evolutionary model. The Qinling Mountains represent a significant geographic barrier in Asia, dividing mainland China into northern (temperate) and southern (semi–tropical) regions; however, their flora has not been well analyzed. In this study, the genetic differentiation and genetic structure of Paeonia rockii and the role of the Qinling Mountains as a barrier that has driven intraspecific fragmentation were evaluated using 14 microsatellite markers.Methodology/Principal FindingsTwenty wild populations were sampled from the distributional range of P. rockii. Significant population differentiation was suggested (FST value of 0.302). Moderate genetic diversity at the population level (HS of 0.516) and high population diversity at the species level (HT of 0.749) were detected. Significant excess homozygosity (FIS of 0.076) and recent population bottlenecks were detected in three populations. Bayesian clusters, population genetic trees and principal coordinate analysis all classified the P. rockii populations into three genetic groups and one admixed Wenxian population. An isolation-by-distance model for P. rockii was suggested by Mantel tests (r = 0.6074, P<0.001) and supported by AMOVA (P<0.001), revealing a significant molecular variance among the groups (11.32%) and their populations (21.22%). These data support the five geographic boundaries surrounding the Qinling Mountains and adjacent areas that were detected with Monmonier's maximum-difference algorithm.Conclusions/SignificanceOur data suggest that the current genetic structure of P. rockii has resulted from the fragmentation of a formerly continuously distributed large population following the restriction of gene flow between populations of this species by the Qinling Mountains. This study provides a fundamental genetic profile for the conservation and responsible exploitation of the extant germplasm of this species and for improving the genetic basis for breeding its cultivars.
Highlights
The patterns of genetic structure in plants are the result of many interacting factors, including climatic fluctuations, complicated landforms, soil types and human activities; a more important factor is the evolutionary history of a species
Significant population differentiation was indicated by the high FST values; we detected moderate genetic diversity at the population level (HS = 0.516, HE = 0.492) and high population diversity (HT = 0.749) at the species level
The finding of high genetic diversity at the species level was similar to the results obtained from three cpDNA sequences in a previous study [10] and from other molecular studies [52,53,54]
Summary
The patterns of genetic structure in plants are the result of many interacting factors, including climatic fluctuations, complicated landforms, soil types and human activities; a more important factor is the evolutionary history of a species. The Qinling Mountains represent an important geographic barrier in Eastern Asia that divides the current mainland of China into southern and northern and temperate and semi–tropical regions. These mountains are a major watershed of the Yellow and Yangtze Rivers. The Qinling Mountains extend for nearly 2,500 kilometers in the east-west direction and are located in a key tectonic position that links the Dabie Mountains in the east with the Qilian and Kunlun Mountains in the west [2] Due to their large area, diversified topography, and varied climates and habitats, the Qinling Mountains have undoubtedly contributed to the evolutionary diversification of the Eastern Asian flora and fauna. The Qinling Mountains represent a significant geographic barrier in Asia, dividing mainland China into northern (temperate) and southern (semi–tropical) regions; their flora has not been well analyzed. The genetic differentiation and genetic structure of Paeonia rockii and the role of the Qinling Mountains as a barrier that has driven intraspecific fragmentation were evaluated using 14 microsatellite markers
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