| 1. |
- Hedrén, Mikael, et al.
(författare)
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Geographical variation and systematics of the tetraploid marsh orchid Dactylorhiza majalis subsp sphagnicola (Orchidaceae) and closely related taxa
- 2012
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Ingår i: Botanical Journal of the Linnean Society. - : Oxford University Press (OUP). - 1095-8339 .- 0024-4074. ; 168:2, s. 174-193
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Tidskriftsartikel (refereegranskat)abstract
- Dactylorhiza majalis subsp. sphagnicola is an allotetraploid marsh orchid derived from parents closely similar to present-day D. incarnata and the western European form of D. maculata subsp. maculata, suggesting that it has a postglacial origin. It extends from northwestern continental Europe into areas formerly covered by the Weichselian ice sheet in mid-Scandinavia. Here, we studied the variation at both the plastid and nuclear marker systems to describe the geographical variation in subsp. sphagnicola and its evolutionary history. We investigated whether subsp. sphagnicola is affected by secondary hybridization and gene flow from its parental lineages or from other allotetraploid marsh orchids, and we also compared subsp. sphagnicola with other allotetraploids of similar origins. We analysed 492 plants from 50 populations. Thirty-seven populations were collected as potential Dactylorhiza majalis subsp. sphagnicola, five as subsp. sesquipedalis (D. elata), one as D. elata subsp. brennensis, one as subsp. calcifugiens, one as subsp. occidentalis and the remaining five as populations with some affinity to subsp. lapponica (including D. traunsteineri). All populations were analysed for plastid haplotypes and nuclear internal transcribed spacer (ITS) allele frequencies, and a subset of 43 populations was analysed for five nuclear microsatellite loci. Dactylorhiza majalis subsp. sphagnicola was dominated by a single plastid haplotype that was also dominant in western European D. maculata subsp. maculata, and most of the alternative haplotypes differed by only one mutation from the dominant one. There was more variation in nuclear microsatellites and ITS, and the variation was geographically structured in these markers. Subspecies occidentalis and calcifugiens shared haplotypes with subsp. sphagnicola, whereas subsp. sesquipedalis and brennensis had other haplotypes. Dactylorhiza majalis subsp. sphagnicola may have a postglacial origin within its present continental distribution. It has incorporated genetic material from D. maculata subsp. maculata by secondary hybridization and introgression, and some northern populations have assimilated strongly divergent haplotypes from the northeastern form of D. maculata subsp. maculata. Subspecies sphagnicola has also evolved morphologically divergent local populations in the north that do not differ from the typical populations in genetic markers. It may form mixed populations with other allotetraploid subspecies of D. majalis and, at least at one site, it has become integrated with subsp. lapponica, demonstrating that independently derived allotetraploids may contribute to a common gene pool. Subspecies calcifugiens seems to be derived from subsp. sphagnicola, and further studies based on a larger sample may confirm that it is better recognized as a variety. The so-called D. elata subsp. brennensis is of hybrid origin and combines markers from subsp. sesquipedalis with markers from the D. majalis core complex, possibly subsp. majalis. The new combination Dactylorhiza majalis subsp. sesquipedalis (Willd.) H.A.Pedersen & Hedren comb. nov. is provided. (C) 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 174193.
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| 2. |
- Hedrén, Mikael, et al.
(författare)
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Plastid and nuclear DNA marker data support the recognition of four tetraploid marsh orchids (Dactylorhiza majalis s.l., Orchidaceae) in Britain and Ireland, but require their recircumscription
- 2011
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Ingår i: Biological Journal of the Linnean Society. - 0024-4066. ; 104:1, s. 107-128
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Tidskriftsartikel (refereegranskat)abstract
- Relationships among allotetraploid marsh orchids collectively assignable to Dactylorhiza majalis s.l. are exceptionally complex because of multiple origins, secondary hybridization with each other, and with their parental lineages, local adaptation, and genomic reorganization processes, all extending through time and space. We sampled 34 populations from Britain and Ireland in an attempt to simultaneously interpret patterns of genetic differentiation within and between populations. The material analysed consisted of 250 individuals that were examined for variation at five nuclear microsatellite loci, internal transcribed spacer (ITS), and plastid DNA. Once integrated, patterns of differentiation in the three molecular data sets show that the British and Irish members of the D. majalis s.l. complex should be assigned to a minimum of four genetically differentiated subgroups of equal status (either species or subspecies), broadly corresponding to the traditional D. majalis ssp. praetermissa, ssp. purpurella, ssp. occidentalis, and ssp. traunsteinerioides. UK plants previously attributed to 'Dactylorhiza lapponica' and given high conservation status have been shown to be genetically identical to ssp. traunsteinerioides. The endemic Hebridean marsh orchid, D. majalis ssp. ebudensis, genetically resembles ssp. traunsteinerioides. Dactylorhiza majalis 'ssp. cambrensis' could readily be accommodated within ssp. purpurella. Together, these observations reinforce a recent assertion that anthocyanin content has been over-weighted in previous morphologically based classifications of Dactylorhiza. Several study populations showed signs of hybridization and introgression with other allotetraploids, or their parental lineages, especially with D. incarnata s.l. However, ssp. praetermissa and ssp. traunsteinerioides were better separated than anticipated: southern populations widely regarded as mixed populations of the two taxa are arguably better treated as containing an unusually narrow-leaved, ecologically specialized form of ssp. praetermissa. Accepting this recircumscription means that the southern margins of the distributions of ssp. purpurella and ssp. traunsteinerioides now coincide, stretching from mid-Wales to the Humber Estuary of Yorkshire, and together indicating a significant genetic transition zone. Plastid haplotype data confirm that ssp. traunsteinerioides and ssp. praetermissa are relatively old polyploids derived from the Continental D. majalis s.l. complex, whereas ssp. purpurella and ssp. occidentalis may have more recent (most likely postglacial) origins within their current distributions. (C) 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 107-128.
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| 3. |
- Hedrén, Mikael, et al.
(författare)
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Systematics and conservation genetics of Dactylorhiza majalis ssp elatior (Orchidaceae) on Gotland
- 2012
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X. ; 30:3, s. 257-272
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Tidskriftsartikel (refereegranskat)abstract
- A tall allotetraploid member of the Dactylorhiza incarnata/maculata complex with unspotted leaves and large pinkish flowers from the island of Gotland in the Baltic was examined for molecular variation patterns at five nuclear microsatellite loci, nuclear ITS and in plastid haplotypes. The allotetraploid was well separated from allopatric allotetraploids of similar appearance, including the western European D. majalis ssp. integrata (syn. D. praetermissa) and forms of D. majalis ssp. lapponica from mainland Sweden. It also differed from other allotetraploids distributed in the Baltic Sea region, including D. majalis ssp. baltica and D. majalis ssp. lapponica. It is here recognized as D. majalis ssp. elatior (Fr.) Hedren & H. A. Pedersen. Dactylorhiza osiliensis Pikner, described from Saaremaa (Estonia) is regarded as a synonym. The distribution covers Gotland, Saaremaa and possibly Hiiumaa. Dactylorhiza majalis ssp. elatior may have one or several recent origins within its present distribution area, and it contains no other molecular markers than those found in the parental D. incarnata var. incarnata and D. maculata ssp. fuchsii in the same area. It appears to have weak barriers towards secondary hybridization with its parental lineages. The situation is reminiscent to that of other young allotetraploids in the D. majalis s.l. complex, suggesting that introgression may be an underestimated process explaining the accumulation of genetic diversity in evolving allopolyploid plants.
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| 4. |
- Hedrén, Mikael, et al.
(författare)
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The polymorphic early marsh orchids, Dactylorhiza incarnata s.l. (Orchidaceae), at Lough Gealain, Ireland
- 2011
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Ingår i: New Journal of Botany. - 2042-3489. ; 1:1, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- Populations of Dactylorhiza incarnata (early marsh orchids) with spotted leaves appear in widely separate parts of Europe including Scandinavia and the Baltic area, the Alps, and Britain and Ireland. Forms with spotted leaves have often been segregated as a separate subspecies, D. incarnata subsp. cruenta. Although previous studies have indicated that the taxon is heterogeneous, it is not known how spotted forms from Britain and Ireland are related to unspotted forms from the same area and how they are related to spotted populations from other parts of Europe. Here, we performed a detailed genetic analysis of the mixed population of spotted and unspotted early marsh orchids at Lough Gealain, County Clare, Ireland in an attempt to shed some light on these questions. A total of 27 plants (11 spotted and 16 unspotted) was examined for genetic variation patterns at three nuclear microsatellite loci and three plastid loci, including one 9-bp deletion and two plastid microsatellites. Spotted and unspotted morphs at Lough Gealain were clearly genetically differentiated from each other, and the total genetic diversity at the site was much better explained by separation into morphs than by separation into subsites along the lake. However, there was still some overlap between morphs at both nuclear microsatellite loci and in plastid haplotypes indicating that at least restricted gene flow occurs. Within each morph, plants growing at close distance from each other seemed to be more closely related than plants growing at larger distances, but the effect was not significant. The spotted morph was affected by some inbreeding, whereas the unspotted morph was not. The spotted morph at Lough Gealain does not agree any more closely with spotted forms of D. incarnata sensu lato from other parts of Europe than with unspotted forms. Both morphs of D. incarnata growing at Lough Gealain contain some fraction of plastid haplotypes that do not occur in any form of the species in the Baltic area, but that are widespread in western Europe, in the Alps, and in Asia Minor. Our results are in agreement with the commonly adopted hypothesis that local segregates of D. incarnata sensu lato may represent genetically divergent groups with restricted gene flow between them. Such patterns could be consistent over local or regional scales, but should not be extrapolated to wider geographic areas in the absence of good supporting molecular data. Spotted forms of D. incarnata growing in different parts of Europe could at most be allocated the rank of variety or forma.
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| 5. |
- Paun, Ovidiu, et al.
(författare)
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Altered gene expression and ecological divergence in sibling allopolyploids of Dactylorhiza (Orchidaceae)
- 2011
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Hybridization and polyploidy are potent forces that have regularly stimulated plant evolution and adaptation. Dactylorhiza majalis s.s., D. traunsteineri s.l. and D. ebudensis are three allopolyploid species of a polyploid complex formed through unidirectional (and, in the first two cases, recurrent) hybridization between the widespread diploids D. fuchsii and D. incarnata. Differing considerably in geographical extent and ecological tolerance, the three allopolyploids together provide a useful system to explore genomic responses to allopolyploidization and reveal their role in adaptation to contrasting environments. Results: Analyses of cDNA-AFLPs show a significant increase in the range of gene expression of these allopolyploid lineages, demonstrating higher potential for phenotypic plasticity than is shown by either parent. Moreover, allopolyploid individuals express significantly more gene variants (including novel alleles) than their parents, providing clear evidence of increased biological complexity following allopolyploidization. More genetic mutations seem to have accumulated in the older D. majalis compared with the younger D. traunsteineri since their respective formation. Conclusions: Multiple origins of the polyploids contribute to differential patterns of gene expression with a distinct geographic structure. However, several transcripts conserved within each allopolyploid taxon differ between taxa, indicating that habitat preferences shape similar expression patterns in these independently formed tetraploids. Statistical signals separate several transcripts - some of them novel in allopolyploids - that appear correlated with adaptive traits and seem to play a role favouring the persistence of individuals in their native environments. In addition to stabilizing the allopolyploid genome, genetic and epigenetic alterations are key determinants of adaptive success of the new polyploid species after recurrent allopolyploidization events, potentially triggering reproductive isolation between the resulting lineages.
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| 6. |
- Paun, Ovidiu, et al.
(författare)
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Stable Epigenetic Effects Impact Adaptation in Allopolyploid Orchids (Dactylorhiza: Orchidaceae)
- 2010
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 27:11, s. 2465-2473
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Tidskriftsartikel (refereegranskat)abstract
- Epigenetic information includes heritable signals that modulate gene expression but are not encoded in the primary nucleotide sequence. We have studied natural epigenetic variation in three allotetraploid sibling orchid species (Dactylorhiza majalis s.str, D. traunsteineri s.l., and D. ebudensis) that differ radically in geography/ecology. The epigenetic variation released by genome doubling has been restructured in species-specific patterns that reflect their recent evolutionary history and have an impact on their ecology and evolution, hundreds of generations after their formation. Using two contrasting approaches that yielded largely congruent results, epigenome scans pinpointed epiloci under divergent selection that correlate with eco-environmental variables, mainly related to water availability and temperature. The stable epigenetic divergence in this group is largely responsible for persistent ecological differences, which then set the stage for species-specific genetic patterns to accumulate in response to further selection and/or drift. Our results strongly suggest a need to expand our current evolutionary framework to encompass a complementary epigenetic dimension when seeking to understand population processes that drive phenotypic evolution and adaptation.
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| 7. |
- Pedersen, Henrik A. E., et al.
(författare)
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On the distinction of Dactylorhiza baltica and D-pardalina (Orchidaceae) and the systematic affinities of geographically intermediate populations
- 2010
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Ingår i: Nordic Journal of Botany. - : Wiley. - 0107-055X .- 1756-1051. ; 28:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- The eastern European Dactylorhiza baltica (Klinge) N. I. Orlova and the western European D. pardalina (Pugsl.) Aver. (= D. praetermissa var. junialis (Verm.) Sengh) are usually considered to have non-overlapping geographic distributions, for which reason it has rarely been realized that they are morphologically similar. They have not previously been thoroughly compared by molecular methods, and no existing flora or revision has convincingly demonstrated that they can be distinguished by morphological characters. In reality, they might be 'political' rather than natural taxa. Prompted by the recent discovery of geographically intermediate populations (in eastern Denmark), originally identified as D. baltica, we have addressed this problem by analysis of morphometric data as well as molecular data from allozyme markers, plastid haplotypes, nuclear ITS alleles and nuclear microsatellites. Dactylorhiza baltica and D. pardalina turned out to be clearly distinguished genetically, and although they are morphologically similar, a few characters were identified that distinguish with 81-85% certainty between the two taxa. Molecular and morphometric data place the geographically intermediate populations in D. pardalina. Both taxa were confirmed to be allotetraploids combining diploid genomes from the D. incarnata s.l. and D. maculata s.l. lineages, and they should therefore be recognized as infraspecic taxa under D. majalis s.l. Thus, D. baltica should be called D. majalis subsp. baltica; D. pardalina is identical with D. praetermissa var. junialis, but the nomenclatural consequences for D. praetermissa, if treated as subspecies under D. majalis, are still unresolved.
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| 8. |
- Soubani, Eman, et al.
(författare)
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Phylogeography of the European rock rose Helianthemum nummularium (Cistaceae): incongruent patterns of differentiation in plastid DNA and morphology
- 2014
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Ingår i: Botanical Journal of the Linnean Society. - : Oxford University Press (OUP). - 1095-8339 .- 0024-4074. ; 176:3, s. 311-331
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Tidskriftsartikel (refereegranskat)abstract
- Helianthemum nummularium is a morphologically variable species that has been subdivided into several subspecies based on indumentum characters. We investigated four of these subspecies for variation in plastid DNA and leaf and petal shape in Europe. Three size-variable mononucleotide repeat regions were amplified by means of species-specific primers and 18 combined haplotypes were identified. The highest haplotype diversity was found in the Alps and the surrounding lowland areas, whereas marginal areas such as northern Europe and the south-eastern Balkans had a lower diversity. Most of the common haplotypes were shared between subspecies and showed a geographical structuring across the range of the species, whereas geographically restricted haplotypes were found elsewhere (e.g. in the Baltic area). Leaf and petal shape descriptors could not differentiate between subspecies. The role of hybridization and introgression between post-glacial migration lineages is discussed. As an alternative hypothesis to introgression between ancient taxa, we suggest that the poor correspondence between plastid haplotype distribution and subspecies circumscription could be a result of multiple origins of similar morphs (grouped into taxonomic subspecies) in different parts of the distribution range of the complex. (c) 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 311-331.
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| 9. |
- Ståhlberg, David, et al.
(författare)
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Evolutionary history of the Dactylorhiza maculata polyploid complex (Orchidaceae)
- 2010
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066. ; 101:3, s. 503-525
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Tidskriftsartikel (refereegranskat)abstract
- Taxonomic complexity may be associated with migration history and polyploidy. We used plastid and nuclear DNA markers to investigate the evolutionary history of the systematically challenging Dactylorhiza maculata polyploid complex. A total of 1833 individuals from 298 populations from throughout Europe were analysed. We found that gene flow was limited between the two major taxa, diploid ssp. fuchsii (including ssp. saccifera) and tetraploid ssp. maculata. A minimum of three autotetraploid lineages were discerned: (1) southern/western ssp. maculata; (2) northern/eastern ssp. maculata; and (3) Central European ssp. fuchsii. The two ssp. maculata lineages, which probably pre-date the last glaciation, form a contact zone with high genetic diversity in central Scandinavia. Intermediate plastid haplotypes in the contact zone hint at recombination. Central Europe may have been a source area for the postglacial migration for the southern/western lineage of ssp. maculata, as well as for ssp. fuchsii. The northern/eastern lineage of ssp. maculata may have survived the LGM in central Russia west of the Urals. The tetraploid lineage of ssp. fuchsii is indistinguishable from diploid ssp. fuchsii, and is probably of postglacial origin. The Mediterranean region and the Caucasus have not contributed to the northward migration of either ssp. fuchsii or ssp. maculata.
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| 10. |
- Travnicek, Pavel, et al.
(författare)
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Minority cytotypes in European populations of the Gymnadenia conopsea complex (Orchidaceae) greatly increase intraspecific and intrapopulation diversity
- 2012
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 110:5, s. 977-986
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Tidskriftsartikel (refereegranskat)abstract
- Patterns of ploidy variation among and within populations can provide valuable insights into the evolutionary mechanisms shaping the dynamics of plant systems showing ploidy diversity. Whereas data on majority ploidies are, by definition, often sufficiently extensive, much less is known about the incidence and evolutionary role of minority cytotypes. Ploidy and proportions of endoreplicated genome were determined using DAPI (4,6-diamidino-2-phenylindole) flow cytometry in 6150 Gymnadenia plants (fragrant orchids) collected from 141 populations in 17 European countries. All widely recognized European species, and several taxa of less certain taxonomic status were sampled within Gymnadenia conopsea sensu lato. Most Gymnadenia populations were taxonomically and/or ploidy heterogeneous. Two majority (2x and 4x) and three minority (3x, 5x and 6x) cytotypes were identified. Evolution largely proceeded at the diploid level, whereas tetraploids were much more geographically and taxonomically restricted. Although minority ploidies constituted 2 of the individuals sampled, they were found in 35 of populations across the entire area investigated. The amount of nuclear DNA, together with the level of progressively partial endoreplication, separated all Gymnadenia species currently widely recognized in Europe. Despite their low frequency, minority cytotypes substantially increase intraspecific and intrapopulation ploidy diversity estimates for fragrant orchids. The cytogenetic structure of Gymnadenia populations is remarkably dynamic and shaped by multiple evolutionary mechanisms, including both the ongoing production of unreduced gametes and heteroploid hybridization. Overall, it is likely that the level of ploidy heterogeneity experienced by most plant species/populations is currently underestimated; intensive sampling is necessary to obtain a holistic picture.
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