| 1. |
- Ayasse, Manfred, et al.
(författare)
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Evolution of reproductive strategies in the sexually deceptive orchid Ophrys sphegodes: How does flower-specific variation of odor signals influence reproductive success?
- 2000
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Ingår i: Evolution. - 1558-5646. ; 54:6, s. 1995-2006
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Tidskriftsartikel (refereegranskat)abstract
- The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population.
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| 2. |
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| 3. |
- Plepys, Dainius, et al.
(författare)
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Odour-mediated nectar foraging in the silver Y moth, Autographa gamma (Lepidoptera : Noctuidae): behavioural and electrophysiological responses to floral volatiles
- 2002
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 99:1, s. 75-82
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Tidskriftsartikel (refereegranskat)abstract
- Naive male and female silver Y moths, Autographa gamma (Lepidoptera: Noctuidae), were attracted in a flight tunnel assay to potted creeping thistle, Cirsium arvense (Asteraceae), butterfly-orchid, Platanthera bifolia (Orchidaceae), soapwort, Saponaria officinalis (Caryophyllaceae), greater knapweed, Centaurea scabiosa (Asteraceae), red clover, Trifolium pratense (Fabaceae), and catnip, Nepeta faasseni (Labiatae), plants with flowers. The most attractive plants were C. arvense, P. bifolia and S. officinalis that elicited 87, 78 and 65%, source contacts, respectively. C. scabiosa was less attractive eliciting 43%, response. T. pratense and N. faasseni showed the least attraction eliciting 28 and 26% source contacts, respectively. A cotton plant used as control, was not attractive. Floral volatiles from the investigated plant species were collected using headspace sampling technique. Samples were analysed using gas chromatography coupled with electroantennographic detection, and electrophysiologically active compounds were identified by coupled gas chromatography/mass spectrometry. Consistent electrophysiological responses were elicited by twelve compounds from headspace of C. arvense, thirteen compounds from P. bifolia, eleven compounds from S. officinalis, nine from C. seabiosa, ten from T. pratense and two from N. faasseni. Most of the active compounds were specific for one or two species, while benzyl benzoate was present in four and benzaldehyde and benzyl alcohol in three species. Floral scents of C. arvense, P. bifolia and S. officinalis, the most attractive flowers, were dominated by aromatic compounds that were not abundant in the scent of other flowers. To conclude, the results demonstrate the absence of a common denominator of odours present in flowers of different plants visited by A. gamma.
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| 4. |
- Plepys, Dainius, et al.
(författare)
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Volatiles from flowers of Platanthera bifolia (Orchidaceae) attractive to the silver Y moth, Autographa gamma (Lepidoptera : Noctuidae)
- 2002
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 99:1, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- We examined the attractiveness of a natural headspace sample of [i]Platanthera bifolia[/i blossoms, synthetic blends and Single compounds to the silver Y moth, Autographa gamma, in a flight tunnel. The synthetic blend consisted of previously identified electrophysiologically active compounds from P. bifolia: benzyl benzoate, benzyl salicylate, cinnamyl alcohol, lilac aldehydes, methyl benzoate and methyl salicylate. This blend had a similar attractivity as the natural headspace sample. Subtraction of lilac aldehydes significantly decreased attractiveness of the synthetic blend. When a mixture of lilac aldehydes was tested alone. it showed attractiveness similar to that of the synthetic blend. One or a mixture of lilac aldehydes accounts for the attraction of moths to P. bifolia. All other Compounds elicited significantly lower responses. Results are discussed in relation to the pollination biology of P. bifolia.
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| 5. |
- Schiestl, Florian P, et al.
(författare)
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Sex pheromone mimicry in the early spider orchid (Ophrys sphegodes): patterns of hydrocarbons as the key mechanism for pollination by sexual deception
- 2000
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Ingår i: Journal of Comparative Physiology A. - : Springer Science and Business Media LLC. - 1432-1351. ; 186:6, s. 567-574
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Tidskriftsartikel (refereegranskat)abstract
- Abstract We investigated the female-produced sex pheromone of the solitary bee Andrena nigroaenea and compared it with floral scent of the sexually deceptive orchid Ophrys sphegodes which is pollinated by Andrena nigroaenea males. We identified physiologically and behaviorally active compounds by gas chromatography with electroantennographic detection, gas chromatography-mass spectrometry, and behavioral tests in the field. Dummies scented with cuticle extracts of virgin females or of O.sphegodes labellum extracts elicited significantly more male reactions than odorless dummies. Therefore, copulation behavior eliciting semiochemicals are located on the surface of the females' cuticle and the surface of the flowers. Within bee and orchid samples, n-alkanes and n-alkenes, aldehydes, esters, all-trans-farnesol and all-trans-farnesyl hexanoate triggered electroantennographic responses in male antennae. Most of the alkanes and alkenes occurred in similar patterns both in the bees and orchids. O. sphegodes leaf extracts contained mostly the same compounds but in different proportions. In behavioral tests with synthetic compounds, blends of alkenes triggered significantly more approaches and pounces of the males whereas alkanes were not more attractive than odorless dummies. Since alkanes and alkenes together were most attractive, we conclude they constitute the bees' sex pheromone as well as the pseudocopulation-behavior releasing orchid-odor bouquet.
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