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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

Scenarios that were tested for the origin of P. × jrtyschensis (pj), P. nigra (pn) and P. laurifolia (pl). N1, N2 and N3 represent current effective population sizes of P. nigra, P. laurifolia and P. × jrtyschensis, respectively. For Scenarios 1–3, t1 is the time of origin of P. × jrtyschensis. t2 represents divergence time between P. nigra and P. laurifolia in “generations ago” and NA is the effective population size of the common ancestor of the three species
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Fig5: Scenarios that were tested for the origin of P. × jrtyschensis (pj), P. nigra (pn) and P. laurifolia (pl). N1, N2 and N3 represent current effective population sizes of P. nigra, P. laurifolia and P. × jrtyschensis, respectively. For Scenarios 1–3, t1 is the time of origin of P. × jrtyschensis. t2 represents divergence time between P. nigra and P. laurifolia in “generations ago” and NA is the effective population size of the common ancestor of the three species

Mentions: We tested three alternative divergence hypotheses for the three taxa based on SSR and nuclear gene data sets separately (Fig. 5). Our ABC modeling results revealed that the hybrid origin model (Scenario 1, Fig. 5) provided a better fit for the observed data than Scenarios 2 and 3. The posterior probabilities of Scenarios 1, 2 and 3 were, respectively, 0.978, 0.004 and 0.0216 for SSRs and 0.382, 0.28 and 0.338 for the nuclear sequence dataset [see Additional file 7]. We tested hybrid composition criteria based on NewHybrids estimates suggested by Anderson and Thompson [36] using SSR and nuclear gene data sets. For SSRs, 95 % of the sampled individuals under P. nigra and 99 % of the sampled individuals under P. laurifolia were pure. In total, 84 % of the sampled individuals of P. × jrtyschensis were considered to be F1 hybrids between pure P. nigra and P. laurifolia. In addition, 6 % of individuals are backcrosses with one of the parents, while it is difficult to ascribe the remaining individuals (Fig. 4). Similarly, based on sequence variations of nuclear genes, 90 and 100 % of the sampled individuals under P. nigra or P. laurifolia were found to be pure. In addition, 87 % of the sampled individuals of P. × jrtyschensis were considered to be F1 hybrids while 9 % of them seems to be backcrosses with one of the parents and the remaining individuals were difficult to ascribe. Only two individuals from one population were found to have the same marked polymorphisms at all 20 SSR loci, suggesting that they derived from the same clone. No single clone was found in any two different populations.Fig. 4


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)

Scenarios that were tested for the origin of P. × jrtyschensis (pj), P. nigra (pn) and P. laurifolia (pl). N1, N2 and N3 represent current effective population sizes of P. nigra, P. laurifolia and P. × jrtyschensis, respectively. For Scenarios 1–3, t1 is the time of origin of P. × jrtyschensis. t2 represents divergence time between P. nigra and P. laurifolia in “generations ago” and NA is the effective population size of the common ancestor of the three species
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig5: Scenarios that were tested for the origin of P. × jrtyschensis (pj), P. nigra (pn) and P. laurifolia (pl). N1, N2 and N3 represent current effective population sizes of P. nigra, P. laurifolia and P. × jrtyschensis, respectively. For Scenarios 1–3, t1 is the time of origin of P. × jrtyschensis. t2 represents divergence time between P. nigra and P. laurifolia in “generations ago” and NA is the effective population size of the common ancestor of the three species
Mentions: We tested three alternative divergence hypotheses for the three taxa based on SSR and nuclear gene data sets separately (Fig. 5). Our ABC modeling results revealed that the hybrid origin model (Scenario 1, Fig. 5) provided a better fit for the observed data than Scenarios 2 and 3. The posterior probabilities of Scenarios 1, 2 and 3 were, respectively, 0.978, 0.004 and 0.0216 for SSRs and 0.382, 0.28 and 0.338 for the nuclear sequence dataset [see Additional file 7]. We tested hybrid composition criteria based on NewHybrids estimates suggested by Anderson and Thompson [36] using SSR and nuclear gene data sets. For SSRs, 95 % of the sampled individuals under P. nigra and 99 % of the sampled individuals under P. laurifolia were pure. In total, 84 % of the sampled individuals of P. × jrtyschensis were considered to be F1 hybrids between pure P. nigra and P. laurifolia. In addition, 6 % of individuals are backcrosses with one of the parents, while it is difficult to ascribe the remaining individuals (Fig. 4). Similarly, based on sequence variations of nuclear genes, 90 and 100 % of the sampled individuals under P. nigra or P. laurifolia were found to be pure. In addition, 87 % of the sampled individuals of P. × jrtyschensis were considered to be F1 hybrids while 9 % of them seems to be backcrosses with one of the parents and the remaining individuals were difficult to ascribe. Only two individuals from one population were found to have the same marked polymorphisms at all 20 SSR loci, suggesting that they derived from the same clone. No single clone was found in any two different populations.Fig. 4

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