PJB-2018-798
Chloroplast DNA-based genetic variation of Rosa roxburghii (Rosaceae) in southwest China: phylogeography and conservation implications
Min Lu
Abstract
Rosa roxburghii Tratt. is a well-known commercial horticultural crop in China with nutritional and medicinal value. Wild germplasms of this rose species are mainly distributed in southwest China but the population number is decreasing due to continuous exploitation, habitat destruction and fragmentation. Therefore, assessing its genetic diversity and phylogeography is important for efficient conservation. Here, two chloroplast intergenic spacers (trnL-trnF and accD-psaI) were investigated in 255 individuals from 29 R. roxburghii populations and 18 haplotypes (H1–H18) were recognized. High levels of haplotype diversity (Hd=0.829) and nucleotide diversity (π =1.3×10−3) were detected in these populations. The genetic variation existed mostly within populations according to an analysis of molecular variance, representing 86.4% of the total variation. A significant correlation between genetic divergence and geographic distance was detected by the Mantel test (r=0.204, P=0.04, 9,999 permutations), indicating the isolation-by-distance model. A significantly higher Nst than Gst (Nst=0.257, Gst=0.136, P<0.05) indicated the phylogeographic structure of R. roxburghii and phylogeographic analysis revealed that its populations experienced a rapid range expansion, probably between 647,073 and 217,848 years ago. The primary processes shaping the genetic patterns of the R. roxburghii populations were restricted gene flow with isolation by distance within clades 1-8, 2-3 and overall, contiguous expansion within clades 1-3 and 3-2, and past fragmentation and/or long-distance colonization within clades 1-9 and 2-2. Conservation priority should be given to the core populations GZ, FQ, DF, DS, xy, AL, LC, PB and XY in the Yunnan-Guizhou Plateau, NZ and MX in the Qingling-Bashan Mountains and MN in the Hengduan Mountains, where an in situ conservation and management strategy should be used.
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