Abstract
Afzelia xylocarpa is listed as an endangered species on the IUCN World list of Threatened Trees, due to over exploitation for its valuable timber and habitat loss, have resulted in a rapid decline of populations size and local population extinction. Understanding of the processes that determine population genetic structure, gene flow and mating systems is important to conserve and manage the existing populations for this endangered tree species. This study describes the level of genetic diversity and differentiation of fifteen populations of A. xylocarpa in Thailand. Genetic variations at seven nuclear microsatellite loci were examined. The seven nuclear microsatellite loci employed detected a total of 53 alleles (n=432). The nSSRs data indicate that a high level of genetic diversity (HS = 0.575) and low level of genetic differentiation among the 15 examined A. xylocarpa populations. The observed level of genetic differentiation among the 15 populations was low, as revealed by FST = 0.074 and GST = 0.078. The results for the nSSRs suggested that all of the populations in North Eastern, Central Thailand and the Klong Lan populations harbored the high genetic diversity and less divergent from the other populations. Therefore, these populations should be assigned the highest priority for conservation of this species. Key words: Afzelia xylocarpa, genetic diversity, endangered species, tropical tree, conservation.
Highlights
Deforestation is one of the most serious threats to biodiversity
This study describes the level of genetic diversity and differentiation of fifteen populations of A. xylocarpa in Thailand
The nSSRs data indicate that a high level of genetic diversity (HS = 0.575) and low level of genetic differentiation among the 15 examined A. xylocarpa populations
Summary
Deforestation is one of the most serious threats to biodiversity. The causes of deforestation are varied, including population pressure, shifting cultivation, agricultural development, transmigration, forest fire and unsupervised, poor logging practices (World Resources Institute, 1991). In Thailand for example, natural forest cover has fallen to less than 20% of the country’s land area, despite 15% of the country being designated conservation areas (Forest Restoration Research Unit, 1998). It causes climatic change, recurrent floods, soil erosion, and loss of fertility, degradation of watersheds, deterioration in the quality of life and loss of wildlife habitats. This result in loss of species populations, reductions in remnant population sizes, changes in densities of reproductive individuals, reduced reproductive success, increased isolation of remnant populations and reduced genetic variability (Prober and Brown, 1994) through genetic bottlenecks and mating systems
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