Despite the prevalent empirical evidence for QST > FST, the results instead suggest a definitive role of stabilizing selection and drift leading to phenotypic differentiation among small populations. Three traits exhibited a significantly lower QST relative to FST, suggesting that populations of P. sinense might have experienced stabilizing selection for the same optimal phenotypes despite large geographical distances between populations and habitat fragmentation. For the other two traits, QST estimates were of the same magnitude as FST, indicating that divergence in these traits could have been achieved by genetic drift alone. The lack of correlation between molecular marker and quantitative genetic variation suggests that sophisticated considerations are required for the inference of conservation measures of P. sinense from neutral genetic markers.

The sand pear (Pyrus pyrifolia Nakai) is an important fruit crop in China. In this study, simple sequence repeats (SSRs) were used to estimate the level and pattern of genetic diversity among 233 sand pear landraces collected from 10 different geographic regions in China. The results demonstrated that the SSR technique is an effective tool for assessing genetic diversity and the geographic pattern of genetic variation among sand pear landraces of different origins. A total of 184 putative alleles was detected using 14 primer pairs with an average of 13.1 alleles per locus. The mean expected heterozygosity and observed heterozygosity across all loci were 0.705 and 0.671, respectively. High genetic diversity was found in all populations except for that originated from Jiangxi (Ae = 3.149; He = 0.655), whereas at the regional level, those from central China were less diverse than those from other regions. Analysis of molecular variance showed that most genetic differences resided among landraces within populations. Additionally, unweighted pair group with arithmetic average clustering and principal component analysis plotting based on Nei's genetic distance revealed distinct gene pools in agreement with geographic distribution.

Twenty-nine primer pairs flanking microsatellite repeats were designed from an AC-enriched genomic library of Psilopeganum sinense and tested using 24 individuals derived from a natural population. A total of 11 microsatellite loci were found polymorphic. The number of alleles per locus varied from two to eight, with an average value of 3.7. The ranges of observed and expected heterozygosities were 0.000-0.750 and 0.365-0.800, respectively. These microsatellite loci have been directly applied to the ongoing conservation genetic studies of P. sinense.

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