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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

Distribution of haplotypes within the three Populus species. a Median-joining network among plastid DNA haplotypes present in P. nigra, P. laurifolia and P. × jrtyschensis. Each sector of a circle is proportional to the frequency of each species in each haplotype. Colors of circles in (b) indicate the species present at a site. In (b) the sectors of circles indicate the frequency of a haplotype in a population at that site
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Fig1: Distribution of haplotypes within the three Populus species. a Median-joining network among plastid DNA haplotypes present in P. nigra, P. laurifolia and P. × jrtyschensis. Each sector of a circle is proportional to the frequency of each species in each haplotype. Colors of circles in (b) indicate the species present at a site. In (b) the sectors of circles indicate the frequency of a haplotype in a population at that site

Mentions: Thirteen substitutions were detected at the rbcL gene across the 566 individuals sampled. These mutations together revealed eight haplotypes (H1-H8, [see Additional file 2]), which clustered into two major groups (Fig. 1): one comprising H2 and the other consisting of H1, H3 and H5-H8. Based on the sequence variations, H4 originated from the recombination of two dominant haplotypes H1 and H2 of the two major groups. Most individuals of P. nigra and P. laurifolia were found to be fixed into a separate group of haplotypes according to species. For example, H2 was associated with most individuals of P. nigra but only one individual of P. laurifolia. In contrast, most individuals of P. laurifolia were H1, while this haplotype was found for only seven individuals of P. nigra. In addition, a few rare haplotypes (H3-H8) were found to be mainly associated with P. laurifolia. The individuals of P. × jrtyschensis that we examined were found to be represented by five haplotypes of both groups, H1, H2, H4, H5 and H6. Around 94 % of the individuals of P. × jrtyschensis were found to have the haplotypes mainly associated with P. laurifolia while 6 % were H2, which is mainly found in P. nigra. Genetic partitions estimated by AMOVA based on these haplotypes revealed that between-population variation was significant and accounted for 34 % of the total variation in P. nigra, but was not significant in P. laurifolia where it accounted for only 6 % of the total variation. Between-population differentiation associated with cpDNA sequence variation was significant in P. × jrtyschensis and accounted for 28 % of the total variation (Table 1).Table 1


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)

Distribution of haplotypes within the three Populus species. a Median-joining network among plastid DNA haplotypes present in P. nigra, P. laurifolia and P. × jrtyschensis. Each sector of a circle is proportional to the frequency of each species in each haplotype. Colors of circles in (b) indicate the species present at a site. In (b) the sectors of circles indicate the frequency of a haplotype in a population at that site
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Distribution of haplotypes within the three Populus species. a Median-joining network among plastid DNA haplotypes present in P. nigra, P. laurifolia and P. × jrtyschensis. Each sector of a circle is proportional to the frequency of each species in each haplotype. Colors of circles in (b) indicate the species present at a site. In (b) the sectors of circles indicate the frequency of a haplotype in a population at that site
Mentions: Thirteen substitutions were detected at the rbcL gene across the 566 individuals sampled. These mutations together revealed eight haplotypes (H1-H8, [see Additional file 2]), which clustered into two major groups (Fig. 1): one comprising H2 and the other consisting of H1, H3 and H5-H8. Based on the sequence variations, H4 originated from the recombination of two dominant haplotypes H1 and H2 of the two major groups. Most individuals of P. nigra and P. laurifolia were found to be fixed into a separate group of haplotypes according to species. For example, H2 was associated with most individuals of P. nigra but only one individual of P. laurifolia. In contrast, most individuals of P. laurifolia were H1, while this haplotype was found for only seven individuals of P. nigra. In addition, a few rare haplotypes (H3-H8) were found to be mainly associated with P. laurifolia. The individuals of P. × jrtyschensis that we examined were found to be represented by five haplotypes of both groups, H1, H2, H4, H5 and H6. Around 94 % of the individuals of P. × jrtyschensis were found to have the haplotypes mainly associated with P. laurifolia while 6 % were H2, which is mainly found in P. nigra. Genetic partitions estimated by AMOVA based on these haplotypes revealed that between-population variation was significant and accounted for 34 % of the total variation in P. nigra, but was not significant in P. laurifolia where it accounted for only 6 % of the total variation. Between-population differentiation associated with cpDNA sequence variation was significant in P. × jrtyschensis and accounted for 28 % of the total variation (Table 1).Table 1

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