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Floral signaling, especially through floral scent, is often highly complex, and little is known about the molecular mechanisms and evolutionary causes of this complexity. In this study, we focused on the evolution of 'floral scent genes' and the associated changes in their functions in three closely related orchid species of the genus Gymnadenia. We developed a benchmark repertoire of 2,571 expressed sequence tags (ESTs) in Gymnadenia odoratissima. For the functional characterization and evolutionary analysis, we focused on eugenol synthase, as eugenol is a widespread and important scent compound. We obtained complete coding complementary DNAs (cDNAs) of two copies of putative eugenol synthase genes in each of the three species. The proteins encoded by these cDNAs were characterized by expression and testing for activity in Escherichia coli. While G. odoratissima and Gymnadenia conopsea enzymes were found to catalyze the formation of eugenol only, the Gymnadenia densiflora proteins synthesize eugenol, as well as a smaller amount of isoeugenol. Finally, we showed that the eugenol and isoeugenol producing gene copies of G. densiflora are evolutionarily derived from the ancestral genes of the other species producing only eugenol. The evolutionary switch from production of one to two compounds evolved under relaxed purifying selection. In conclusion, our study shows the molecular bases of eugenol and isoeugenol production and suggests that an evolutionary transition in a single gene can lead to an increased complexity in floral scent emitted by plants. [ABSTRACT FROM AUTHOR]

Patterns and levels of genetic diversity mayhave significant influence on the long termpersistence of local populations and revealingsuch information is important in protectingrare species. In this study we investigated thegenetic pattern in five microsatellite lociwithin five Swedish populations of the rareorchid species Gymnadenia odoratissima. Thegeographic distribution of G. odoratissima isrestricted to Europe and in Scandinavia it isonly found in three provinces in southernSweden; Östergötland,Västergötland and on the island ofGotland.Compared with the more widespread congener G.conopsea our results indicate lower levels ofgenetic variation within and higher degrees ofgenetic differentiation among populations of G. odoratissima (HEL = 0.6–0.8 in G. conopseaand 0.3–0.7 in G. odoratissima; FST over allpopulations = 0.06 in G. conopsea and 0.19 in G. odoratissima). Also, we found a cleardistinction among mainland and islandpopulations of G. odoratissima wherepopulations on the island of Gotland seem toexhibit higher levels of gene flow andintragenetic variation, probably as a result ofa larger number of existing populations.Future conservation of this species shouldfocus on facilitation on colonisation events,especially on the mainland, and preservation ofthe genetically more variable Gotlandpopulations. [ABSTRACT FROM AUTHOR]

Ten species of orchid plants belonging to the genera Orchis (7), Dactylorhiza (2), and Gymnadenia (1) were analyzed by enzyme electrophoresis. Each species can be identified by a combination of enzyme bands different from those of all other species examined. The electrophoretic data were used for the construction of phenetic and phylogenetic trees with the help of computer programs. The trees were almost identical regardless which method was used. Our results differ considerably from a classification based on morphological evidence. The electrophoretic data indicate that the genus Orchis is not a monophyletic group. [ABSTRACT FROM AUTHOR]

The digitate-tubered clade (Dactylorhiza s.l. plus Gymnadenia s.l.) within subtribe Orchidinae is an important element of the North-temperate orchid flora and has become a model system for studying the genetic and epigenetic consequences of organism-wide ploidy change. Here, we integrate morphological phylogenetics with Sanger sequencing of nrITS and the plastid region trnL-F in order to explore phylogenetic relationships and phenotypic character evolution within the clade. The resulting morphological phylogenies are strongly incongruent with the molecular phylogenies, instead reconstructing through parsimony the genus-level boundaries recognised by traditional 20th Century taxonomy. They raise fresh doubts concerning whether Pseudorchis is sister to Platanthera or to Dactylorhiza plus Gymnadenia. Constraining the morphological matrix to the topology derived from ITS sequences increased tree length by 20%, adding considerably to the already exceptional level of phenotypic homoplasy. Both molecular and morphological trees agree that D. viridis and D. iberica are the earliest-diverging species within Dactylorhiza (emphasising the redundancy of the former genus Coeloglossum). Morphology and ITS both suggest that the former genus Nigritella is nested within (and thus part of) Gymnadenia, the Pyrenean endemic 'N.' gabasiana apparently forming a molecular bridge between the two radically contrasting core phenotypes. Comparatively short subtending molecular branches plus widespread (though sporadic) hybridisation indicate that Dactylorhiza and Gymnadenia approximate the minimum level of molecular divergence acceptable in sister genera. They share similar tuber morphologies and base chromosome numbers, and both genera are unusually prone to polyploid speciation. Another prominent feature of multiple speciation events within Gymnadenia is floral paedomorphosis. The 'traditional' morphological and candidate-gene approaches to phylogeny reconstruction are critically appraised. [ABSTRACT FROM AUTHOR]