Riporto di seguito i lavori e pubblicazioni che ho trovato finora relativi a Gymnadenia conopsea s.l., compresi i tre precedentemente segnalati. Quando disponibile l'intero articolo, ho riportato il link del pdf.
Moseler BM. 1987
Zur morphologischen, phanologischen und standortlichen charakterisierung von Gymnadenia conopsea (L.) R.BR. subsp. densiflora (Wahlenb.) K.Richter.
Flor. Rundbr. 21. (1): 8-18
Marco Soliva e Alex Widmer, 1999
Genetic and floral divergence among sympatric populations of Gymnadenia conopsea sl (Orchideaceae) with different flowering phenology.
International journal of plant sciences, 160 (5): 897-905.
Abstract:Gymnadenia conopsea s.l. is a common orchid in central Europe, where early- and late-flowering populations can be distinguished. The early-flowering form is recognized as subspecies conopsea and the late-flowering form as subspecies densiflora. The two subspecies can occur in sympatry, but their flowering periods are separated. We investigated whether early- and late-flowering subspecies are genetically differentiated, whether they diverged once or repeatedly, and we tried to identify potential evolutionary forces involved in the divergence of the two subspecies. We used genetic markers to estimate genetic divergence within and among populations of early- and late-flowering G. conopsea, and to reconstruct their evolutionary history. In addition, we assessed morphological variation between subspecies. Allozyme variation indicated that subspecies conopsea was significantly more variable than subsp. densiflora and that gene flow among populations of subsp. conopsea was higher than among populations of subsp. densiflora. Gene flow between subspecies was low, indicating that the difference in flowering phenology represented an effective barrier to gene flow. A neighbor-joining tree based on allozyme frequencies indicated that early- and late- flowering populations did not diverge repeatedly in sympatry. Levels of cpDNA variation were generally low, even between G. conopsea s.l. and Gymnadenia odoratissima, chosen as an outgroup. Four cpDNA haplotypes were found, which differed only in the number of microsatellite repeats. Their distribution among subspecies of G. conopsea s.l. and G. odoratissima indicates that microsatellite haplotypes have evolved repeatedly, and their occurrence in different taxa thus represents a homoplasy. Floral characters were variable within and among populations and subspecies but did not consistently separate early- from late-flowering populations. A weak separation between subspecies was found in vegetative characters that presumably reflected habitat and competitive differences experienced by early- and late-flowering populations.
Gustafsson, S. 2003.
Population genetic analyses in the orchid genus Gymnadenia – a conservation genetic perspective.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 799. 43 pp
Small populations are facing a particular risk of extinction due to a lack of appropriate genetic diversity and associated negative effects, factors dealt with in the discipline of conservation genetics. Many orchid species exhibit characteristics that make them a perfect study object in the scope of conservation genetics. The aim with this thesis was to investigate genetic structure at different levels in two orchid species Gymnadenia conopsea, geographically widespread, although diminishing and G. odoratissima with a long history of being rare. Microsatellite markers, developed in and used in studies of G. conopsea were also used in the study of G. odoratissima. Populations of G. conopsea expressed high levels of genetic variation and a certain amount of gene flow, although investigated mating pattern in a small population indicated non-random mating among individuals, with the majority of pollen exchange between near neighbours, and noticeable levels of geitonogamous pollinations. Further a pronounced year to year variation in flowering frequency among individuals was found. It was also discovered that flowering time variants (early and late) within the species G. conopsea were highly differentiated and seem to have had a more ancient historical separation than the separation between the two different species, G. conopsea and G. odoratissima. Levels of genetic variation in the rare congener, G. odoratissima differed between island and mainland populations where the more numerous island populations expressed larger levels of genetic variation and were less differentiated compared to the few remaining and genetically depauperated mainland populations.
http://uu.diva-portal.org/smash/get/div ... FULLTEXT01S Gustafsson and M Lönn - 2003
Genetic differentiation and habitat preference of flowering-time variants within Gymnadenia conopsea,
Heredity 91, 284–292
AbstractUsing fast-evolving microsatellites, more slowly evolving ITS markers and performing habitat analyses, we demonstrated a drastic genetic divergence and significant habitat differentiation between early- and late-flowering variants of plants morphologically belonging to Gymnadenia conopsea ssp conopsea. The two phenological variants can either be found in separate or in mixed populations. Information from microsatellite markers and ITS sequences indicated the occurrence of an early historical split between the two flowering-time variants, a split that has been maintained until the present time even within sympatric populations. Early-flowering variants were also far more genetically diverse, had more alleles per microsatellite locus and a wider habitat amplitude than late-flowering variants. As a comparison, we included G. odoratissima in the sequencing study. We found G. odoratissima to be most closely related to the early- flowering type. This indicates a more ancient divergence event between the two flowering-time variants within G. conopsea ssp conopsea than between the two different species G. odoratissima and the early-flowering variant of G. conopsea. Possible explanations to the results arrived at and possible mechanisms maintaining the genetic separation are discussed.
http://www.nature.com/hdy/journal/v91/n ... 00334a.pdfK.Marhold, I.Jongepierová, A.Krahulcová & J.Kucera - 2005
Morphological and karyological differentiation of Gymnadenia densiflora and Gymnadenia conopsea in the Czech Republic and Slovakia.
Preslia, Praha, 77: 159–176.
AbstractGymnadenia densiflora was recently either misinterpreted or not accepted as a distinct taxon by several authors. To resolve its taxonomic position and differentiation from the related G. conopsea, a detailed study of the morphology, chromosome numbers and distribution of these two taxa in the Czech Republic, Slovakia and neighbouring areas was carried out. Chromosome counts showed an invariable diploid chromosome number (2n = 40) for G. densiflora, while G. conopsea is diploid, tetraploid and rarely also pentaploid (2n = 40, 80, 100). Results of morphometric analyses (principal component analysis, cluster analysis, classificatory and canonical discriminant analysis) confirmed a good morphological separation between G. densiflora and G. conopsea. Characters such as the width of the second lowermost leaf, height of the plant, number of flowers in the inflorescence, number of leaves, and the ratio of height of the plant and distance from the stem base to the base of the uppermost sheathed leaf contributed most to this separation. Our study supports the recognition of G. densiflora as a distinct species.
http://ibot.sav.sk/usr/Karol/docs/PDF_f ... 52CMar.pdfLonn, M., Alexandersson, R. and Gustafsson, S. 2006
Hybrids and fruit set in a mixed flowering-time population of Gymnadenia conopsea (Orchidaceae).
Hereditas 143: 222228. Lund, Sweden. eISSN 1601-5223.
AbstractWe have recently found that the morphologically determined subspecies Gymnadenia conopsea ssp conopsea in Sweden includes early and late flowering individuals. We were interested in the interactions between the flowering time groups; if there were gene flow between them and if so this was detrimental or advantageous. A spatially mixed population of early and late flowering individuals was studied using three microsatellite loci. We measured patterns in genetic differentiation and inferred occurrence of hybridisation and introgression. Variation in flowering time, fertility and relative and absolute fruit set was measured. The pattern of introgression between flowering-time groups differed between loci. In two of the three investigated loci, allele separation was distinct between early and late flowering plants and one genetically obvious hybrid was infertile. In the third locus, several alleles were shared between the two flowering time variants. The degree of introgression was associated to fruit set failure, which was higher in the late flowering plants and lower in early flowering plants.
A small group of early flowering individuals with somewhat delayed flowering compared to the main group was genetically distinct and had lower relative and absolute fruit set. This group was not genetically intermediate, but rather constituting an independent group, with lower fruit set possibly caused by absence of pollinators. There seem to be a strong barrier against introgression into the late flowering group which is kept genetically distinct and less diverse. The early flowering group is diverse, includes two subgroups and seems to benefit from gene flow.
http://onlinelibrary.wiley.com/doi/10.1 ... 1958.×/pdfVICTORIA V. CAMPBELL, GRAHAM ROWE, TREVOR J. C. BEEBEE, MICHAEL J. HUTCHINGS, 2007
Genetic differentiation amongst fragrant orchids (Gymnadenia conopsea s.l.) in the British Isles
The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 349–360.
AbstractGenetic variation was examined in five microsatellite loci to seek evidence of genetic differentiation and restricted gene flow that would support the taxonomic division of Gymnadenia into three species (G. borealis, G. conopsea, and G. densiflora). A total of 107 alleles was detected in 17 populations from England, Scotland, and Ireland. The mean expected heterozygosities ranged from 0.48 to 0.81. The differentiation in allele frequencies amongst populations that had been assigned to each taxon on the basis of morphology was sufficiently large to support the taxa as distinct species. Phylogenetic trees based on microsatellite allele frequencies, as well as assignment tests, supported the existence of three distinct groups with at least partial restriction of gene flow between them. There was substantial homozygote excess, leading to high FIS estimates, for most loci in most populations. This is unlikely to have been a result of widespread null alleles, and more probably reflects a high level of inbreeding in G. conopsea. This inference requires further investigation. The implications of the results of this and other taxonomic studies for the conservation of Gymnadenia in Britain are discussed.
MATHEW S. BOX, RICHARD M. BATEMAN, BEVERLEY J. GLOVER, PAULA J. RUDALL, 2008
Floral ontogenetic evidence of repeated speciation via paedomorphosis in subtribe Orchidinae (Orchidaceae)
Botanical Journal of the Linnean Society, Volume 157, Issue 3, pages 429–454,
AbstractThoroughly sampled molecular phylogenies of the dominantly European orchid subtribe Orchidinae were used to identify a pair and a triplet of recently diverged species in which: (1) divergence involved substantial changes in floral morphology, particularly in the labellar lobes and spur; and (2) the polarity of those changes could be inferred phylogenetically. Floral ontogeny in the selected species was documented in detail through macromorphological, light microscopic, and scanning electron microscopic study of a wide range of ontogenetic stages. All study species showed differentiation of perianth segments earlier than the gynostemium. Unsurprisingly, component parts of the basic floral organs (gymnostemial auricles and rostellum, labellar lateral lobes, and spur) were initiated relatively late, the spur and ovary continuing to expand beyond anthesis. The predominant evolutionary pattern identified in the two case studies was paedomorphosis via progenesis (earlier offset of growth); this credibly explained the reduction in spur size and lateral lobing of the labellum in Gymnadenia odoratissima and, especially, G. austriaca relative to G. conopsea. Loss of resupination in G. austriaca was best viewed as the deletion of a formerly terminal ontogenetic stage. Radical reduction of the spur of Dactylorhiza viridis relative to D. fuchsii was also attributed to progenesis, although the long, narrow outline and relatively short central lobe of its labellum were attributed to increased growth of the lateral lobes (i.e. hypermorphosis resulting in peramorphosis). Microscopic study of epidermal cell types on the labellum and spur suggested a degree of decoupling of micromorphological from macromorphological transitions, although both were subject to heterochronic shifts. Each of the two case studies was consistent with, but not proof of, saltational macroevolution operating via functional changes in one or more key developmental genes. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 429–454.
Christiane Starka, Wieslaw Babikb, Walter Durka, 2009
Fungi from the roots of the common terrestrial orchid Gymnadenia conopsea
Mycological Research, 113, (9): 952–959.
AbstractThe fungal community associated with the terrestrial photosynthetic orchid Gymnadenia conopsea was characterized through PCR-amplification directly from root extracted DNA and cloning of the PCR products. Six populations in two geographically distinct regions in Germany were investigated. New ITS-primers amplifying a wide taxonomic range including Basidiomycetes and Ascomycetes revealed a high taxonomic and ecological diversity of fungal associates, including typical orchid mycorrhizas of the Tulasnellaceae and Ceratobasidiaceae as well as several ectomycorrhizal taxa of the Pezizales. The wide spectrum of potential mycorrhizal partners may contribute to this orchid's ability to colonize different habitat types with their characteristic microbial communities. The fungal community of G. conopsea showed a clear spatial structure. With 43 % shared taxa the species composition of the two regions showed only little overlap. Regardless of regions, populations were highly variable concerning taxon richness, varying between 5 and 14 taxa per population. The spatial structure and the continuous presence of mycorrhizal taxa on the one hand and the low specificity towards certain fungal taxa on the other hand suggest that the fungal community associated with G. conopsea is determined by multiple factors. In this context, germination as well as pronounced morphological and genetic differentiation within G. conopsea deserve attention as potential factors affecting the composition of the fungal community.
http://www.eko.uj.edu.pl/molecol/images ... a_2009.pdfNina Sletvold and Jon Ågren, 2010
Pollinator-Mediated Selection on Floral Display and Spur Length in the Orchid Gymnadenia conopsea.
International Journal of Plant Sciences Vol. 171, No. 9, pp. 999-1009
AbstractFloral diversification and specialization are thought to be driven largely by interactions with pollinators, but the extent to which current selection on floral traits is mediated by pollinators has rarely been determined experimentally. We documented selection through female function on floral traits in two populations of the rewarding orchid Gymnadenia conopsea in two years and quantified pollinator-mediated selection (?ßpoll) by subtracting estimates of selection gradients for plants receiving supplemental hand pollination from estimates obtained for open-pollinated control plants. There was directional selection for taller plants, more flowers, larger corollas, and longer spurs in the study populations. Pollinator-mediated selection ranged from weak to moderately strong (?ßpoll, range -0.01–0.21, median 0.08). All observed selection on spur length could be attributed to interactions with pollinators, while the proportion of observed selection on plant height (0%–77%), number of flowers (13%–42%), and corolla size (13%–97%) caused by pollinators varied among populations and years. Our results demonstrate that pollinators can mediate selection on both traits likely to be involved in pollinator attraction and traits affecting pollination efficiency. They further show that spatiotemporal variation in the strength of pollinator-mediated selection can contribute substantially to differences in selection between years and populations.
Christiane Stark, 2010 -
Tesi di dottoratoPopulation genetics on anthropogenic and natural sites, subspecies differentiation and fungal community of Gymnadenia conopsea s.l. (Orchidaceae)
AbstractToday human impact is the main driver of global environmental change. One of the most severe anthropogenic changes is land transformation, which has altered 40- 50% of Earth’s surface into urban and agricultural systems. Orchids are particularly vulnerable to environmental changes, because with germination and pollination two important life cycle stages directly depend on symbiotic interactions. Therefore a thorough understanding of orchid biology and the factors that determine habitat suitability and orchid distribution is essential for an effective conservation of orchid diversity. Using Gymnadenia conopsea s.l. as study system, a common orchid that occurs over a wide ecological amplitude, this thesis addresses aspects of orchid biology that might be critical for orchid recruitment and the long-term persistence of populations in the wild, namely the specificity of the mycorrhizal symbiosis, population genetic diversity and genetic differentiation. The availability of suitable fungal partners is a precondition for orchid germination in the wild as they provide carbohydrates for initial growth. In one study the fungal communities of six G. conopsea s.str. populations in two study regions in East and North Germany were analysed. The 28 identified taxa revealed a high diversity of fungi associated with G. conopsea. This high diversity of associated fungi indicates that this orchid shows only little specificity to certain fungal clades, which is likely to contribute to its ability to grow in very different habitat types with the respective fungal communities. However, the taxon composition showed a clear spatial structure and only little overlap between regions, suggesting that factors at the local scale may strongly affect local species composition and hence diversity at the regional level. In all populations taxa of the known OM genera Tulasnella, Ceratobasidium, Thanatephorus and Sebacina were detected, suggesting that G. conopsea utilizes typical OM fungi as mycorrhizas. However, also ascomycetous taxa from the Pezizales and Helotiales were identified. Their continuous detection indicates that this orchid is also able to utilize ascomycetous ectomycorrhizal taxa, which could be another aspect contributing to its ability to grow in a variety of different habitats. Many orchids are well known as primary colonisers and are often found in anthropogenic habitats. In order to assess whether founder effects during colonization threaten the long-term survival of recently established populations, another study compared the genetic diversity and fitness of populations from anthropogenically disturbed and surrounding natural habitats in two German regions (East Germany: lignite post-mining area; North Germany: quarries). The results revealed a reduced genetic diversity and lowered fruit set for the populations in the lignite post-mining area, whereas no such effects were found for the quarry populations. However, the general plant performance was similar for all investigated populations. This indicates that during the colonization of post-mining areas that are often distant from potential source populations, founder effects may occur. In contrast, this problem seems negligible for G. conopsea populations in the quarries, which were spatially intermixed with source populations. Gymnadenia conopsea (L.) R.BR. s.l. is a controversial taxon. The two most commonly distinguished taxa are G. conopsea (L.) R.BR. subsp. conopsea and G. conopsea subsp. densiflora (WAHLENB.) K. RICHT., for which also a species status has been suggested. Due to a high morphological overlap between the taxa, identification in the field is difficult. Hence, for taxon assignment all investigated populations were genetically and morphologically analyzed. The analysis of the ITS region revealed a 2% nucleotide divergence, similar to the divergence between other Gymnadenia species. This, together with largely non-overlapping sets of microsatellite alleles supports the view that Gymnadenia conopsea (L.) R.BR. s.str. and Gymnadenia densiflora (WAHLENB.) DIETRICH deserve species status. G. conopsea s.str. and G. densiflora are not even sister species as the sequences of G. densiflora form a well supported monophyletic group, sharing a most recent common ancestor with G. nigra and G. austriaca. G. conopsea s.str. was either diploid or tetraploid, while G. densiflora was diploid throughout. As the microsatellite patterns of the two ploidy levels of G. conopsea s.str. were hardly differentiated and the most frequent ITS haplotypes occurred in both of them, an autopolyploid origin of tetraploid from diploid G. conopsea s.str. is likely. However, morphological differentiation was less clear. Although some traits (e.g. flower number and density) allow a fairly good distinction, due to a considerable variation an unequivocal identification will remain difficult.
http://archiv.ub.uni-marburg.de/diss/z2011/0106/Jana Jersáková, Sílvia Castro, Nicole Sonk, Kathrin Milchreit, Iva Schödelbauerová, Till Tolasch and Stefan Dötterl, 2010
Absence of pollinator-mediated premating barriers in mixed-ploidy populations of Gymnadenia conopsea s.l. (Orchidaceae)
EVOLUTIONARY ECOLOGY Volume 24, Number 5 (2010), 1199-1218
AbstractPolyploidy has played a key role in plant evolution and diversification. Despite this, the processes governing reproductive isolation among cytotypes growing in mixed-ploidy populations are still largely unknown. Theoretically, coexistence of diploid and polyploid individuals in sympatric populations is unlikely unless cytotypes are prezygotically isolated through assortative pollination. Here, we investigated the pre-mating barriers involved in the maintenance of three co-occurring cytotypes from the genus Gymnadenia (Orchidaceae): tetraploid and octoploid G. conopsea and tetraploid G. densiflora. We assessed differences in flowering phenology, floral morphology, and visual and olfactory cues, which could lead to assortative mating. Gas chromatography coupled with electroantennographic detection was used to identify scent compounds with physiological activity in the two main pollinators, Deilephila porcellus and Autographa gamma. The importance of olfactory cues was also assessed in the field by analysing the moths’ responses to the olfactory display of the plants, and by following the pollinator’s behaviour on artificial arrays. Our complex approach demonstrated that the coexistence of Gymnadenia cytotypes in mixed-ploidy populations was only partly explained by differences in floral phenology, as cytotypes with overlapping flowering (i.e., octoploid G. conopsea and tetraploid G. densiflora) might freely exchange pollen due to only 1 mm differences in spur lengths and the lack of assortative behaviour of pollinators. While floral colour among the cytotypes was similar, floral scent differed significantly. Though both pollinator species seemed to physiologically detect these differences, and the floral scent alone was sufficient to attract them, pollinators did not use this cue to discriminate the cytotypes in the field. The absence of pre-mating barriers among cytotypes, except partial temporal segregation, suggests the existence of other mechanisms involved in the cytotypes’ coexistence. The genetic differences in ITS sequences among cytotypes were used to discuss the cytotype’s origin.
Pavel Tràvnìcek, Barbora Kubàtovà, Vladislav Curn, Jana Rauchovà, Eva Krajnìkovà, Jana Jersàkovà and Jan Suda, 2011
Remarkable coexistence of multiple cytotypes of the Gymnadenia conopsea aggregate (the fragrant orchid): evidence from flow cytometry
Annals of Botany 107: 77–87,
Background and Aims One of the prerequisites for polyploid research in natural systems is knowledge of the geographical distribution of cytotypes. Here inter- and intrapopulational ploidy diversity was examined in the Gymnadenia conopsea aggregate in central Europe and potential explanations and evolutionary consequences of the observed spatial patterns investigated.
Methods DAPI flow cytometry supplemented by confirmatory chromosome counts was used to determine ploidy in 3581 samples of the G. conopsea aggregate from 43 populations. The fine-scale spatial pattern of cytotype distribution (intra- and interploidy associations) was analysed with univariate and bivariate K-functions.
Key Results Gymnadenia tissues undergo a progressively partial endoreplication, which accounts for about 60 % and 75 % of the total genome in G. conopsea and G. densiflora, respectively. Flow cytometric profiles are therefore species-specific and can be used as a marker for rapid and reliable species recognition. Two majority (4x, 8x) and three minority (6x, 10x, 12x) cytotypes were found, often in mixed-ploidy populations (harbouring up to all five different ploidy levels). The scarcity of the minority cytotypes (about 2.7 %) suggests the existence of strong pre- or postzygotic mating barriers. Spatial structure was observed in plots of populations with the highest cytotype variation, including clumping of individuals of the same ploidy and negative association between tetra- and octoploids.
Conclusions The remarkable ploidy coexistence in the G. conopsea aggregate has reshaped our perception of intrapopulational ploidy diversity under natural conditions. This system offers unique opportunities for studying processes governing the formation and establishment of polyploids and assessing the evolutionary significance of the various pre- and postzygotic mating barriers that maintain this ploidy mixture.
http://aob.oxfordjournals.org/content/107/1/77.full.pdfhttp://ktisis.cut.ac.cy/bitstream/10488 ... ct%202.pdfChristiane Stark, Stefan G. Michalski, Wiesław Babik, Grit Winterfeld, Walter Durka, 2011
Strong genetic differentiation between Gymnadenia conopsea and G. densiflora despite morphological similarity
Plant Systematics and Evolution 293: 213–226
The fragrant orchid Gymnadenia conopsea s.l. is a controversial taxon with two commonly distinguished species, G. conopsea s.str. and G. densiflora. Despite morphological similarity, differentiation between the taxa has been reported for several characters; however, character variation within taxa has obviated a clear consensus. We assessed ITS sequences, microsatellite variation and chromosome numbers on the European scale (1,420 samples) and conducted morphological analyses for 626 samples from Germany. ITS analysis revealed a 2% nucleotide divergence between the taxa, similar to the divergence between other Gymnadenia species. The ITS sequences of G. densiflora form a well-supported monophyletic group sharing a most recent common ancestor with G. nigra and G. austriaca. Thus, G. conopsea and G. densiflora are not sister species, and a species rank is supported for G. densiflora (Wahlenb.) Dietrich and G. conopsea (L.) R.BR. s.str. This was confirmed by the microsatellite analysis, which revealed a strong genetic differentiation between the taxa because of largely non-overlapping sets of alleles. Chromosome numbers showed that G. conopsea was either diploid or tetraploid, whereas G. densiflora was diploid throughout. Morphologically, the taxa differed significantly in the mean value of a number of diagnostic characters. However, a discriminant analysis showed that the morphological variability is substantial, and on the individual level an unequivocal assignment is not possible as 96% of G. conopsea, but only 77% of G. densiflora could be assigned correctly. Further studies are needed on character variation within and among species and ploidy levels to allow for a better identification of the genetically differentiated but morphologically similar taxa.
http://www.ufz.de/export/data/1/22231_S ... l_2011.pdfALOK KUMAR GUPTA, 2011 - Tesi di laurea
Identification, characterization, and evolutionary patterns of floral fragrance genes in Gymnadenia and Silene species.
Dalhousie University, Canada
Abstract
Plants release an array of chemical compounds that play a key role in mediating plant-insect interactions. Floral scents are chemically complex blends of low-molecular weight volatile organic compounds (VOCs) that not only attract pollinators but can also deter herbivores and ants from causing harm to the plants’ reproductive structures. Though plants tend to synthesize and produce hundreds of volatile compounds, only a small subset of these are found to be
perceived by pollinators and to elicit behavioral responses. Quantitative and qualitative variation in the emission of such scent compounds may be responsible for assortative flower-visitation and thereby, can drive reproductive isolation between co-flowering species. Knowledge of the genetic basis of scent production, the evolutionary processes shaping scent composition, and variation in this complex floral signal are essential for understanding the dynamics of plantpollinator adaptations. Until recently, most studies on volatile-associated enzyme biochemistry and gene cloning have been conducted on a few model species, such as Clarkia, Petunia, Antirrhinum, and Rosa, while less progress has been made for non-model plants. As a result, to date, nothing is known about how scent is produced and regulated in lepidoptera-pollinated Gymnadenia and Silene species at the molecular level, where floral scent has a key role in ensuring pollination. The aims of this thesis were to elucidate the molecular basis of scent synthesis in fragrant Gymnadenia (Orchidaceae) and Silene (Caryophyllaceae) species, and to study the evolutionary patterns of scent-specific genes in these focal species. As a first step (Chapter I), a benchmark Gymnadenia odoratissima sequence resource of 3,456 expressed sequence tags (ESTs) was developed for the identification of floral and especially floral scent-related genes. The floral EST sequences of putative eugenol synthase genes were further used to obtain full-length cDNAs encoding G. odoratissima eugenol synthase1 (GoEGS1), G. odoratissima eugenol synthase 2 (GoEGS2), G. conopsea eugenol synthase1 (GcEGS1), G. conopsea eugenol synthase 2 (GcEGS2), G. densiflora (iso)-eugenol synthase1 (GdIEGS1) and G. densiflora (iso) eugenol synthase2 (GdIEGS2). Results of the biochemical analyses illustrate that most of the identified Gymnadenia NADPH-dependent enzymes in this study catalyze the formation of eugenol, except GdIEGS1 and GdIEGS2 that catalyze the formation of eugenol and trace amounts of isoeugenol. To date, no such NADPH-dependent enzyme has been characterized that is responsible for the formation of a mixture of phenylpropene regio-isomers. Furthermore, our evolutionary analysis suggests that a switch from production of one (eugenol) to two compounds (eugenol and isoeugenol) evolved under relaxed purifying selection. [...] The thesis presented here provides the foundations of two new plant systems, Silene and Gymnadenia, for scent-molecular research. In addition, functionally characterized fragrance genes and their evolutionary patterns are relevant for understanding pollinator-mediated selection on floral scent variation and thereby, expand our knowledge of traits that contribute to reproductive isolation among closely related plant species.
http://e-collection.library.ethz.ch/ese ... 503-01.pdf
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In particolare, in una stazione che conosco molto bene, sita ad una cinquantina di metri da dove abito, il pendio collinare discende piuttosto ripido, esposto ad est e piuttosto in ombra perché collocato in una stretta valletta, alternando una facies superiore di sabbie gialle, tipiche del pliocene astigiano e uno strato argilloso più profondo, che affiora verso il fondo della riva (argille grigio-azzurre del piacenziano). In piena estate (luglio - agosto) appare come un luogo arido, ma in primavera e autunno, soprattutto dopo le lunghe pioggie, compare la vera natura di quel terreno... tante piccole risorgive da cui "butta" costantemente un filo d'acqua, che generano piccoli rigagnoli, che rendono tutta la scarpata un ambiente ideale per la crescita di queste orchidee! Di seguito una foto di una Gymnadenia conopsea subsp. densiflora di questa stazione della provincia di Asti ancora in boccio... in piena fioritura supera i 110 cm! Seguita per tre anni consecutivi, l'altezza finale variava di pochissimi cm, con una infiorescenza di circa 280-300 fiori! Tale sottospecie, oltre che per l'altezza e per l'infiorescenza così densa, si distingue dalla sottospecie nominale per la disposizione delle foglie, che sono tutte addensate alla base, e sono più lunghe e più larghe di quelle della subsp. nominale. Per quanto riguarda le differenze nel periodo di fioritura non ho avuto modo di osservare differenze significative. In realtà alcuni studi sostengono che dove questa forma cresce con la subsp. conopsea, quest'ultima tende a fiorire due settimane prima, ma mi sembra un periodo talmente breve e soggetto a possibili variazioni stagionali, da non essere un parametro così certo di distinzione.
