The endangered Dipterocarpus dyeri is distributed in forests of southeast Vietnam, which is expected to have low genetic diversity and high genetic population structure due to habitat loss and overexploitation. To provide valuable information for conservation measures, nine polymorphic microsatellites were used to analyze 151 adult trees from six populations, representing the natural range of D. dyeri in Vietnam. Contrary to the expectation, this species has relatively high genetic diversity within populations, low genetic differentiation among populations, and suggesting high gene flow. Results of bottleneck tests showed evidence of a bottleneck in the TaKou population. Analysis of molecular variance showed a high genetic variation within populations compared to among populations. Bayesian analysis also indicated two genetic lineages related to geographical distances. These results highlight the importance of conserving the genetic resources of D. dyeri and will provide guidelines for species conservation in Vietnam.
Panax vietnamensis Ha et Grushv. is a precious medicinal species native to the tropical forests of Vietnam. Due to habitat loss and over-harvesting, this species is endangered in Vietnam. To conserve the species, we investigated genetic variability and population structure using nine microsatellites for 148 individuals from seven populations across the current distribution range of P. vietnamensis in Vietnam. We determined a moderate genetic diversity within populations (HO = 0.367, HE = 0.437) and relatively low population differentiation (the Weir and Cockerham index of 0.172 and the Hedrick index of 0.254) and showed significant differentiation (P < 0.05), which suggested fragmented habitats, over-utilization and over-harvesting of P. vietnamensis. Different clustering methods revealed that individuals were grouped into two major clusters, which were associated with gene flow across the geographical range of P. vietnamensis. This study also detected that ginseng populations can have undergone a recent bottleneck. We recommend measures in future P. vietnamensis conservation and breeding programs.
AFLP -amplified fragment length polymorphism; AMOVA -variance components molecular variance; CR -critically endangered; DAPC -discriminant analysis of principal components; FIS -fixation index; FISIIM -corrected inbreeding coefficient for null alleles; HE -expected heterozygosity; HO -observed heterozygosity; HT -total expected heterozygosity; HWE -Hardy-Weinberg equilibrium; ISSR -inter simple sequence repeat markers; IUCN -international union for conservation of nature; NA -alleles per locus; NE -effective alleles; NJ -neighbor-joining; NP -private alleles; NR -allelic richness; PcoA -principal coordinate analysis; PCRpolymerase chain reaction; PPL -proportion of polymorphic loci; RAPD -random amplified polymorphic DNA; SMM -the stepwise mutation model; SSR -microsatellite; Tm -PCR annealing temperature; TPM -the two-phase model. Acknowledgements: This research was funded by Vietnam national Foundation for Science and Technology Development (NAFOSTED) under grant number 106. 06-2018.310.
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