Genetic Diversity Of The Endangered Plant Species, Disanthus Cercidifolius Subsp. Longipes

Genetic diversity is of critical importance for a species to maintain its evolutionary potential to cope with ever-changing environment, and loss of genetic diversity is often associated with reduced fitness. Therefore, the maintenance of genetic variation is very important for conservation of endangered species. Eight microsatellite markers were used to investigate genetic diversity in 10 natural populations of Disanthus cercidifolius subsp. longipes, an endangered shrub endemic to China. The results demonstrated that:1.8 highly polymorphic primer pairs were selected from 20 microsatellite loci, which were proved reproducible and reliable in amplifying D. cercidifolius subsp. longipes genomic DNA. These molecular markers were used in genetic analysis of D. cercidifolius subsp. longipes.2.52 alleles were identified at 8 microsatelite loci across 256 individuals from 10 natural D. Cercidifolius subsp. longipes populations, and the mean number of alleles was 6.5 per locus. The most was 12 at locus DC013, and the least was 4 at loci DC185 and DC426, respectively.3. Acorss ten populations, average Polymorephic Information Content (PIC) at 8 loci was between 0.161-0.824, observed heterozygosity ranged from 0.203-0.445. expected heterozygosity ranged from 0.367-0.551. Across loci, observed heterozygosity ranged from 0.132-0.629, the mean was 0.345, expected heterozygosity ranged from 0.169-0.845, the mean was 0.545.4. Hardy-Weinberg equilibrium tests revealed that there were 53 out of 80 population-locus pairs shifted from HWE, which indicated that unrandom mating occurred among individuals within populations.5. The Nei's unbiased genetic identity between populations ranged from 0.686 to 0.946. The Nei's standard genetic distance (D) between populations ranged from 0.056 to 0.376, the maximum occurred between LQ and JG populations, and the minimum occurred between YZ and DX populations. There was significant genetic differentiation between every two populations, this result was also validated in AMOVA.6. UPGMA cluster analysis showed that every population clustered by their geographic location except two population (JG and YF) from Jiangxi Province, which clustered with KH and XN, respectively. It should be explored further.7. Mantel tests of correlation between genetic and geographical distance of pairwise populations showed that there was a marginally significant correlation between genetic and geographical distance (r2=0.055, P=0.073, slope=0.48), which may be affected by the two special populations (JG and YF).In conclusion, Disanthus cercidifolius subsp. longipes displayed comparatively high level of genetic diversity, but there was significant genetic divergence between populations. The comparatively high level of genetic diversity may closely correlate with its longevity, outcrossing and long evolutionary history in this shrub. However, the advantage of life history traits did not counteract the negative impacts of habitat fragmentation and restricted seed dispersal, which hold back gene flow within and among populations. These may significantly reduce genetic variability within populations and increase genetic divergence among populations.