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Genetic origin and composition of a natural hybrid poplar Populus × jrtyschensis from two distantly related species.

Jiang D, Feng J, Dong M, Wu G, Mao K, Liu J - BMC Plant Biol. (2016)

Bottom Line: Two groups of cpDNA haplotypes characteristic of P. nigra and P. laurifolia respectively were both recovered for P. × jrtyschensis.Genetic structures and coalescent tests of two sets of nuclear population genetic data suggested that P. × jrtyschensis originated from hybridizations between the two assumed parental species.In the habitats of P. × jrtyschensis, there are lower concentrations of soil nitrogen than in the habitats occupied by the other two species.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Grassland Agro-Ecosystem, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, People's Republic of China.

ABSTRACT

Background: The factors that contribute to and maintain hybrid zones between distinct species are highly variable, depending on hybrid origins, frequencies and fitness. In this study, we aimed to examine genetic origins, compositions and possible maintenance of Populus × jrtyschensis, an assumed natural hybrid between two distantly related species. This hybrid poplar occurs mainly on the floodplains along the river valleys between the overlapping distributions of the two putative parents.

Results: We collected 566 individuals from 45 typical populations of P. × jrtyschensis, P. nigra and P. laurifolia. We genotyped them based on the sequence variations of one maternally inherited chloroplast DNA (cpDNA) fragment and genetic polymorphisms at 20 SSR loci. We further sequenced eight nuclear genes for 168 individuals from 31 populations. Two groups of cpDNA haplotypes characteristic of P. nigra and P. laurifolia respectively were both recovered for P. × jrtyschensis. Genetic structures and coalescent tests of two sets of nuclear population genetic data suggested that P. × jrtyschensis originated from hybridizations between the two assumed parental species. All examined populations of P. × jrtyschensis comprise mainly F1 hybrids from interspecific hybridizations between P. nigra and P. laurifolia. In the habitats of P. × jrtyschensis, there are lower concentrations of soil nitrogen than in the habitats occupied by the other two species.

Conclusions: Our extensive examination of the genetic composition of P. × jrtyschensis suggested that it is typical of F1-dominated hybrid zones. This finding plus the low concentration of soil nitrogen in the floodplain soils support the F1-dominated bounded hybrid superiority hypothesis of hybrid zone maintenance for this particular hybrid poplar.

No MeSH data available.


Related in: MedlinePlus

Genetic clustering of all individuals of P. nigra, P. laurifolia and P. × jrtyschensis. a Principal Component Analysis (PCA), b NeighborNet (NNet), and c Population cluster analysis using STRUCTURE (K = 2 and 3) based on nuclear gene dataset; d Principal Component Analysis (PCA), e NeighborNet (NNet), and f Population cluster analysis using STRUCTURE (K = 2 to 3) based on SSR datasets
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Fig3: Genetic clustering of all individuals of P. nigra, P. laurifolia and P. × jrtyschensis. a Principal Component Analysis (PCA), b NeighborNet (NNet), and c Population cluster analysis using STRUCTURE (K = 2 and 3) based on nuclear gene dataset; d Principal Component Analysis (PCA), e NeighborNet (NNet), and f Population cluster analysis using STRUCTURE (K = 2 to 3) based on SSR datasets

Mentions: Sequence variation and genetic diversity across the eight nuclear loci were both larger in P. × jrtyschensis than in the other two species [see Additional file 3]. Private single-nucleotide polymorphisms (SNPs) for each parent species were recovered at each locus, with shared SNPs being more common between P. × jrtyschensis and P. nigra than between P. × jrtyschensis and P. laurifolia (Table 2). Both PCAs of samples and the NNet tree constructed for all samples suggested a hybrid origin of P. × jrtyschensis (Fig. 3a, b). Structure also revealed that when K was set to 2 in Structure with USEPOPINFO = 1, P. nigra and P. laurifolia individuals clustered into two separate groups, while individuals of P. × jrtyschensis were admixed, containing a mixture of the genomes of the two groups representing the putative parent species (Fig. 3c). Both the Pritchard et al. [34] and Evanno et al. [35] tests indicated that the most likely number of clusters for the entire data set was K = 2. Genetic divergence between the three taxa further indicated that P. × jrtyschensis was a hybrid, in that divergence between P. × jrtyschensis and either P. nigra or P. laurifolia was similar, while pairwise Φst values for comparisons between P. × jrtyschensis and either P. nigra or P. laurifolia were lower than between P. nigra and P. laurifolia (Fig. 2) [see Additional file 4]. In each taxa, the positive values for both Tajima’s D and Fu & Li’s D and F were estimated for half of the nuclear loci and negative for the others [see Additional file 3].Table 2


Genetic origin and composition of a natural hybrid poplar Populus × jrtyschensis from two distantly related species.

Jiang D, Feng J, Dong M, Wu G, Mao K, Liu J - BMC Plant Biol. (2016)

Genetic clustering of all individuals of P. nigra, P. laurifolia and P. × jrtyschensis. a Principal Component Analysis (PCA), b NeighborNet (NNet), and c Population cluster analysis using STRUCTURE (K = 2 and 3) based on nuclear gene dataset; d Principal Component Analysis (PCA), e NeighborNet (NNet), and f Population cluster analysis using STRUCTURE (K = 2 to 3) based on SSR datasets
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4836070&req=5

Fig3: Genetic clustering of all individuals of P. nigra, P. laurifolia and P. × jrtyschensis. a Principal Component Analysis (PCA), b NeighborNet (NNet), and c Population cluster analysis using STRUCTURE (K = 2 and 3) based on nuclear gene dataset; d Principal Component Analysis (PCA), e NeighborNet (NNet), and f Population cluster analysis using STRUCTURE (K = 2 to 3) based on SSR datasets
Mentions: Sequence variation and genetic diversity across the eight nuclear loci were both larger in P. × jrtyschensis than in the other two species [see Additional file 3]. Private single-nucleotide polymorphisms (SNPs) for each parent species were recovered at each locus, with shared SNPs being more common between P. × jrtyschensis and P. nigra than between P. × jrtyschensis and P. laurifolia (Table 2). Both PCAs of samples and the NNet tree constructed for all samples suggested a hybrid origin of P. × jrtyschensis (Fig. 3a, b). Structure also revealed that when K was set to 2 in Structure with USEPOPINFO = 1, P. nigra and P. laurifolia individuals clustered into two separate groups, while individuals of P. × jrtyschensis were admixed, containing a mixture of the genomes of the two groups representing the putative parent species (Fig. 3c). Both the Pritchard et al. [34] and Evanno et al. [35] tests indicated that the most likely number of clusters for the entire data set was K = 2. Genetic divergence between the three taxa further indicated that P. × jrtyschensis was a hybrid, in that divergence between P. × jrtyschensis and either P. nigra or P. laurifolia was similar, while pairwise Φst values for comparisons between P. × jrtyschensis and either P. nigra or P. laurifolia were lower than between P. nigra and P. laurifolia (Fig. 2) [see Additional file 4]. In each taxa, the positive values for both Tajima’s D and Fu & Li’s D and F were estimated for half of the nuclear loci and negative for the others [see Additional file 3].Table 2

Bottom Line: Two groups of cpDNA haplotypes characteristic of P. nigra and P. laurifolia respectively were both recovered for P. × jrtyschensis.Genetic structures and coalescent tests of two sets of nuclear population genetic data suggested that P. × jrtyschensis originated from hybridizations between the two assumed parental species.In the habitats of P. × jrtyschensis, there are lower concentrations of soil nitrogen than in the habitats occupied by the other two species.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Grassland Agro-Ecosystem, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, People's Republic of China.

ABSTRACT

Background: The factors that contribute to and maintain hybrid zones between distinct species are highly variable, depending on hybrid origins, frequencies and fitness. In this study, we aimed to examine genetic origins, compositions and possible maintenance of Populus × jrtyschensis, an assumed natural hybrid between two distantly related species. This hybrid poplar occurs mainly on the floodplains along the river valleys between the overlapping distributions of the two putative parents.

Results: We collected 566 individuals from 45 typical populations of P. × jrtyschensis, P. nigra and P. laurifolia. We genotyped them based on the sequence variations of one maternally inherited chloroplast DNA (cpDNA) fragment and genetic polymorphisms at 20 SSR loci. We further sequenced eight nuclear genes for 168 individuals from 31 populations. Two groups of cpDNA haplotypes characteristic of P. nigra and P. laurifolia respectively were both recovered for P. × jrtyschensis. Genetic structures and coalescent tests of two sets of nuclear population genetic data suggested that P. × jrtyschensis originated from hybridizations between the two assumed parental species. All examined populations of P. × jrtyschensis comprise mainly F1 hybrids from interspecific hybridizations between P. nigra and P. laurifolia. In the habitats of P. × jrtyschensis, there are lower concentrations of soil nitrogen than in the habitats occupied by the other two species.

Conclusions: Our extensive examination of the genetic composition of P. × jrtyschensis suggested that it is typical of F1-dominated hybrid zones. This finding plus the low concentration of soil nitrogen in the floodplain soils support the F1-dominated bounded hybrid superiority hypothesis of hybrid zone maintenance for this particular hybrid poplar.

No MeSH data available.


Related in: MedlinePlus