Population genetic analysis of Xylia xylocarpa (Fabaceae—Mimosoideae) in Thailand
2015
Wattanakulpakin, Tanat | Iamtham, Siriluck | Grubbs, Kunsiri Chaw | Volkaert, Hugo A.
The genetic diversity of Xylia xylocarpa (Roxb.) W. Theob. var. kerrii I. C. Nielsen in Thailand was studied using molecular markers. The results revealed a large diversity within and moderate differentiation between populations that could be correlated with geography. Samples were collected from individual trees in 16 populations. Eight single-locus nuclear gene markers were used to identify different alleles using PCR–single-strand conformation polymorphism (SSCP) combined with sequencing. For easier detection of some alleles, 10 SNPs were converted into cleaved amplified polymorphic sequence (CAPS) assays and 5 SNPs were converted to allele-specific PCR (AS-PCR) assays. From 10 to 33 alleles were identified for the different loci. The effective number of alleles was much lower, ranging between 1.1 and 7.6, as several of the alleles were found at low frequency in just one or a small number of populations. Several loci showed deviation from the Hardy–Weinberg equilibrium. A high level of gene flow was estimated. The largest genetic distances calculated according to Nei (Gₛₜ) and Jost (Dₑₛₜ) were found between populations from the northeast and the west of Thailand. STRUCTURE analysis revealed support for population differentiation in two or three clusters, though genetic distances between the clusters were small. Four populations from western Thailand separated from the others, as did the three populations from northeastern Thailand. The large number of low-frequency alleles would make conservation of genetic resources in this species a difficult task as a large number of populations and individuals will need to be protected.
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