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Patterns of hybridization between diploid and derived allotetraploid species of Dactylorhiza (Orchidaceae) co-occurring in Belgium

(2011) AMERICAN JOURNAL OF BOTANY. 98(6). p.946-955
Author
Organization
Abstract
Premise of the study : Although the potential for gene flow between species with large differences in chromosome numbers has long been recognized, only few studies have thoroughly investigated in situ hybridization across taxa with different ploidy levels. We combined morphological, cytological, and genetic marker data with pollination experiments to investigate the degree, direction, and spatial pattern of hybridization between the diploid Dactylorhiza incarnata and its tetraploid derivative, D. praetermissa. Methods : To identify hybrids, 169 individuals were genotyped using AFLPs and morphologically characterized. Individuals were clustered on the basis of their AFLP profile using the program Structure. To reduce the dimensionality of the plant-trait matrix, PCA was applied. The origin of suspected hybrid individuals was verified using flow cytometry. An AMOVA and spatial autocorrelation analysis were used to indirectly infer the extent of gene flow. Key results : Only five individuals were regarded as putative hybrids on the basis of the AFLP data; all had been assigned to the D. praetermissa morphotype. Only one had deviating DNA content and was presumably a triploid. High Phi(ST) values between different subpopulations and significant spatial genetic structure were observed, suggesting localized gene flow. Conclusions : Using combined data to study hybridization between D. incarnata and D. praetermissa, very few unequivocal hybrids were observed. We propose several non-mutually exclusive explanations. Localized pollen flow, in combination with different microhabitat preferences, is probably one of the reasons for the low frequency of hybrids. Also, the triploid first-generation hybrids may experience difficulties in successful establishment, as a result of genic incompatibilities.
Keywords
morphology, genetic analysis, polyploidy, spatial genetic structure, SPATIAL GENETIC-STRUCTURE, MOLECULAR CHARACTERIZATION, INCARNATA ORCHIDACEAE, POLYPLOID EVOLUTION, PLANT HYBRIDIZATION, DECEPTIVE ORCHID, HYBRID ZONES, POPULATIONS, CONSERVATION, PURPUREA, gene flow, D. praetermissa, Dactylorhiza incarnata, AFLP

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Chicago
De Hert, K, H Jacquemyn, S Van Glabeke, Isabel Roldàn-Ruiz, K Vandepitte, L Leus, and O Honnay. 2011. “Patterns of Hybridization Between Diploid and Derived Allotetraploid Species of Dactylorhiza (Orchidaceae) Co-occurring in Belgium.” American Journal of Botany 98 (6): 946–955.
APA
De Hert, K, Jacquemyn, H., Van Glabeke, S., Roldàn-Ruiz, I., Vandepitte, K., Leus, L., & Honnay, O. (2011). Patterns of hybridization between diploid and derived allotetraploid species of Dactylorhiza (Orchidaceae) co-occurring in Belgium. AMERICAN JOURNAL OF BOTANY, 98(6), 946–955.
Vancouver
1.
De Hert K, Jacquemyn H, Van Glabeke S, Roldàn-Ruiz I, Vandepitte K, Leus L, et al. Patterns of hybridization between diploid and derived allotetraploid species of Dactylorhiza (Orchidaceae) co-occurring in Belgium. AMERICAN JOURNAL OF BOTANY. 2011;98(6):946–55.
MLA
De Hert, K, H Jacquemyn, S Van Glabeke, et al. “Patterns of Hybridization Between Diploid and Derived Allotetraploid Species of Dactylorhiza (Orchidaceae) Co-occurring in Belgium.” AMERICAN JOURNAL OF BOTANY 98.6 (2011): 946–955. Print.
@article{8096181,
  abstract     = {Premise of the study : Although the potential for gene flow between species with large differences in chromosome numbers has long been recognized, only few studies have thoroughly investigated in situ hybridization across taxa with different ploidy levels. We combined morphological, cytological, and genetic marker data with pollination experiments to investigate the degree, direction, and spatial pattern of hybridization between the diploid Dactylorhiza incarnata and its tetraploid derivative, D. praetermissa. 
Methods : To identify hybrids, 169 individuals were genotyped using AFLPs and morphologically characterized. Individuals were clustered on the basis of their AFLP profile using the program Structure. To reduce the dimensionality of the plant-trait matrix, PCA was applied. The origin of suspected hybrid individuals was verified using flow cytometry. An AMOVA and spatial autocorrelation analysis were used to indirectly infer the extent of gene flow. 
Key results : Only five individuals were regarded as putative hybrids on the basis of the AFLP data; all had been assigned to the D. praetermissa morphotype. Only one had deviating DNA content and was presumably a triploid. High Phi(ST) values between different subpopulations and significant spatial genetic structure were observed, suggesting localized gene flow. 
Conclusions : Using combined data to study hybridization between D. incarnata and D. praetermissa, very few unequivocal hybrids were observed. We propose several non-mutually exclusive explanations. Localized pollen flow, in combination with different microhabitat preferences, is probably one of the reasons for the low frequency of hybrids. Also, the triploid first-generation hybrids may experience difficulties in successful establishment, as a result of genic incompatibilities.},
  author       = {De Hert, K and Jacquemyn, H and Van Glabeke, S and Rold{\`a}n-Ruiz, Isabel and Vandepitte, K and Leus, L and Honnay, O},
  issn         = {0002-9122},
  journal      = {AMERICAN JOURNAL OF BOTANY},
  language     = {eng},
  number       = {6},
  pages        = {946--955},
  title        = {Patterns of hybridization between diploid and derived allotetraploid species of Dactylorhiza (Orchidaceae) co-occurring in Belgium},
  url          = {http://dx.doi.org/10.3732/ajb.1000367},
  volume       = {98},
  year         = {2011},
}

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