ABSTRACT. Dipterocarpus alatus (Dipterocarpaceae) is widely distributed in lowland forests in central and southern Vietnam, Cambodia, Laos, Myanmar, Philippines, Thailand, and India. Due to over-exploitation and habitat destruction, the species is now threatened. The genetic variation within and among populations of D. alatus was investigated on the basis of 9 microsatellite (single sequence repeat, SSR) loci. In all, 268 sampled trees from 10 populations in central and southern Vietnam were analyzed in this study. The SSR data showed Analysis of molecular variance showed that most genetic variation was within populations (74.96%). This study highlights the importance of conserving the genetic resources of D. alatus species.

Dipterocarpus dyeri is an endangered species in lowland tropical forests of Vietnam because of habitat fragmentation and over-exploitation of this species. It plays an important economic and ecological role in Vietnam. Due to the importance and lack of information on its genetic diversity and mating system, we investigated genetic parameters in adults and juveniles of this species in two natural populations about 10 km apart. Eight polymorphic microsatellite loci were analysed and showed high genetic diversity in adults (H O = 0.475-0.563, H E = 0.551-0.649) and juveniles (H O = 0.47-0.513, H E = 0.576-0.685) in both populations. Results revealed differences of genetic diversity between two adult (F ST = 0.123) and two juvenile populations (F ST = 0.188). However, the differences were negligible and indicated that the fragmented habitat had negligible effect on genetic diversity. Gene flow or gene migration between two populations in adults or juveniles remained (N m > 1), although this value reduced slightly in the latter. Analysis of the mating system indicated high outcrossing rate of D. dyeri (t m = 0.8). Biparental mating (t m -t s ) was relatively high (0.19-0.25) and suggested high tendency of mating system between relatives. Genetic conservation should derive from correlated outcrossing.

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ABSTRACT. Dipterocarpus costatus is an endangered species restricted to the lowland forests of southern Vietnam. Habitat loss and over-exploitation of D. costatus wood are the major threats to this species. We investigated the level of genetic variability within and among populations of D. costatus in order to provide guidelines for the conservation, management, and restoration of this species to the Forest Protection Department, Vietnam. respectively, in the lowland forests of southeast Vietnam. The low genetic diversity might be a consequence of inbreeding within the small and isolated populations of D. costatus owing to its habitat loss and over-exploitation. All populations deviated from Hardy-Weinberg equilibrium showing reduced heterozygosity. Alleles were lost from the populations by genetic drift. Genetic differentiation among populations was high (average pairwise F ST = 0.405), indicating low gene flow (<1) and isolated populations due to its destructed habitat and large geographical distances (P < 0.05) among populations. Heterozygosity excess tests (except of Bu Gia Map only under infinite allele model) were negative. The high genetic variation (62.7%) was found within populations. The STRUCTURE and neighbor joining tree results suggest strong differentiation among D. costatus populations, with the three genetic clusters, Phu Quoc, Tan Phu and Bu Gia Map, and Lo Go-Xa Mat due to habitat fragmentation and isolation. The threatened status of D. costatus was related to a lack of genetic diversity, with all its populations isolated in small forest patches. We recommend the establishment of an ex situ conservation site for D. costatus with a new big population comprising all genetic groups in order to enhance its survival under different environmental stresses.

DNA barcoding is a useful tool for species identification using standardized genomic DNA fragments. We used DNA barcodes (ITS-rDNA and matK gene) to explore Panax (32 samples collected from Phu Xai Lai Leng mountain and 19 samples collected from medicinal nursery of TH), and to investigate the phylogenetic taxonomy of Panax. In this study, the PCR success rate for ITS-rDNA and matK region was 100%. The success rate of bidirectional sequencing of PCR product was 100% of ITS-rDNA and matK region with length of 616 bp, 1433 bp, respectively. All 32 samples (Panax TB) of Phu Xai Lai Leng have a close relationship with P. stipuleanatus (MLBS = 99%, BPP = 100%). All 19 samples (Panax TH) of medicinal nursery have a close relationship with P. notoginseng (MLBS = 100%, BPP = 100%). Interspecific genetic distances within and among Panax species was varied from 0.2% to 7.9%, average (4%) (ITS-rDNA gene) and 0.1 to 2.9%, average (1.2%) (matK gene). The genetic relationship of species/gender belonging to the Panax genus showed that they have the same evolutionary origin and discovered that new distributed of P. stipuleanatus in Phu Xai Lai Leng mountain in Vietnam.

Pinus armandii subsp. xuannhaensis L.K. Phan is a new five needle pine discovered recently from Xuan Nha Nature Reserve, Son La province. This subspecies is considered as a narrow endemic to Vietnam and is assessed as endangered. In this study, 15 ISSR markers were used to analyze the genetic diversity of this taxon collected in five subpopulations (Tan Xuan, Thac Nuoc, Dinh VTV2, Near VTV2 and Dinh Pomu). Results of the analysis showed 15/15 markers were polymorphic. A total of 51 DNA fragments were amplified, in which 50 fragments were polymorphic (98.04%). Genetic diversity was the highest in Dinh Pomu subpopulation (I = 0.555; h = 0.8; PPB = 68.76%; Ne =1.6 and He = 0.4)) and the lowest in Tan Xuan subpopulation (I = 0.428; h = 0.6; PPB = 57.06%, Ne = 1.215 and He = 0.303). Analysis of molecular variance (AMOVA) results showed that the total level of molecular changes between subpopulations was 7% and between individuals in the same subpopulation was 93%. A constructed dendrogram based on similarity matrix of 71 Pinus armandii subsp. xuannhaensis L.K. Phan samples divided the samples into two main groups with genetic similarity coefficients ranged from 0.53 to 0.96. Results of the molecular analysis showed that Pinus armandii subsp. xuannhaensis L.K. Phan species should be protected at the population level.

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