1,721,005 research outputs found
Hybrid floral scent novelty drives pollinator shift in sexually deceptive orchids
Full text linksee also the coverage by the BBC (http://news.bbc.co.uk/2/hi/science/nature/8632814.stm), the related articles in "Le Soir" and "EOS Sciences" and the commentary by MW Chase et al. in BMC Biology (http://www.biomedcentral.com/content/pdf/1741-7007-8-45.pdf).info:eu-repo/semantics/publishe
Variability in floral scent in rewarding and deceptive orchids - the signature of pollinator-imposed selection?
Full text linkBackground and Aims A comparative investigation was made of floral scent variation in the closely related, food-rewarding Anacamptis coriophora and the food-deceptive Anacamptis morio in order to identify patterns of variability of odour compounds in the two species and their role in pollinator attraction/avoidance learning. Methods Scent was collected from plants in natural populations and samples were analysed via quantitative gas chromatography and mass spectrometry. Combined gas chromatography and electroantennographic detection was used to identify compounds that are detected by the pollinators. Experimental reduction of scent variability was performed in the field with plots of A. morio plants supplemented with a uniform amount of anisaldehyde. Key Results Both orchid species emitted complex odour bouquets. In A. coriophora the two main benzenoid compounds, hydroquinone dimethyl ether (1,4-dimethoxybenzene) and anisaldehyde (methoxybenzaldehyde), triggered electrophysiological responses in olfactory neurons of honey-bee and bumble-bee workers. The scent of A. morio, however, was too weak to elicit any electrophysiological responses. The overall variation in scent was significantly lower in the rewarding A. coriophora than in the deceptive A. morio, suggesting pollinator avoidance-learning selecting for high variation in the deceptive species. A. morio flowers supplemented with non-variable scent in plot experiments, however, did not show significantly reduced pollination success. Conclusions Whereas in the rewarding A. coriophora stabilizing selection imposed by floral constancy of the pollinators may reduce scent variability, in the deceptive A. morio the emitted scent seems to be too weak to be detected by pollinators and thus its high variability may result from relaxed selection on this floral trai
Pollinator attraction in Anacamptis papilionacea (Orchidaceae): a food or a sex promise?
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Do floral and ecogeographic isolation allow the co-occurrence of two ecotypes of Anacamptis papilionacea (Orchidaceae)?
Full text linkEcotypes are relatively frequent in flowering plants and considered central in ecological speciation as local adaptation can promote the insurgence of reproductive isolation. Without geographic isolation, gene flow usually homogenizes the allopatrically generated phenotypic and ecological divergences, unless other forms of reproductive isolation keep them separated. Here, we investigated two orchid ecotypes with marked phenotypic floral divergence that coexist in contact zones. We found that the two ecotypes show different ecological habitat preferences with one being more climatically restricted than the other. The ecotypes remain clearly morphologically differentiated both in allopatry and in sympatry and differed in diverse floral traits. Despite only slightly different flowering times, the two ecotypes achieved floral isolation thanks to different pollination strategies. We found that both ecotypes attract a wide range of insects, but the ratio of male/female attracted by the two ecotypes was significantly different, with one ecotype mainly attracts male pollinators, while the other mainly attracts female pollinators. As a potential consequence, the two ecotypes show different pollen transfer efficiency. Experimental plots with pollen staining showed a higher proportion of intra- than interecotype movements confirming floral isolation between ecotypes in sympatry while crossing experiments excluded evident postmating barriers. Even if not completely halting the interecotypes pollen flow in sympatry, such incipient switch in pollination strategy between ecotypes may represent a first step on the path toward evolution of sexual mimicry in Orchidinae
Putative Signals of Generalist Plant Species Adaptation to Local Pollinator Communities and Abiotic Factors
No full textThe reproductive success of flowering plants with generalized pollination systems is influenced by interactions with a diverse pollinator community and abiotic factors. However, knowledge about the adaptative potential of plants to complex ecological networks and the underlying genetic mechanisms is still limited. Based on a pool-sequencing approach of 21 natural populations of Brassica incana in Southern Italy, we combined a genome-environmental association analysis with a genome scan for signals of population genomic differentiation to discover genetic variants associated with the ecological variation. We identified genomic regions putatively involved in the adaptation of B. incana to the identity of local pollinator functional categories and pollinator community composition. Interestingly, we observed several shared candidate genes associated with long-tongue bees, soil texture, and temperature variation. We established a genomic map of potential generalist flowering plant local adaptation to complex biotic interactions, and the importance of considering multiple environmental factors to describe the adaptive landscape of plant populations
Pollinator convergence and the nature of species' boundaries in sympatric Sardinian Ophrys (Orchidaceae)
No full text† Background and Aims In the sexually deceptive Ophrys genus, species isolation is generally considered ethological
and occurs via different, specific pollinators, but there are cases in which Ophrys species can share a
common pollinator and differ in pollen placement on the body of the insect. In that condition, species are
expected to be reproductively isolated through a pre-mating mechanical barrier. Here, the relative contribution
of pre- vs. post-mating barriers to gene flow among two Ophrys species that share a common pollinator and
can occur in sympatry is studied.
† Methods A natural hybrid zone on Sardinia between O. iricolor and O. incubacea, sharing Andrena morio as
pollinator, was investigated by analysing floral traits involved in pollinator attraction as odour extracts both for
non-active and active compounds and for labellum morphology. The genetic architecture of the hybrid zone
was also estimated with amplified fragment length polymorphism (AFLP) markers, and pollination fitness and
seed set of both parental species and their hybrids in the sympatric zone were estimated by controlled crosses.
† Key Results Although hybrids were intermediate between parental species in labellum morphology and nonactive
odour compounds, both parental species and hybrids produced a similar odour bouquet for active compounds.
However, hybrids produced significantly lower fruit and seed set than parental species, and the
genetic architecture of the hybrid zone suggests that they were mostly first-generation hybrids.
†Conclusions The two parental species hybridize in sympatry as a consequence of pollinator overlap and weak
mechanical isolation, but post-zygotic barriers reduce hybrid frequency and fitness, and prevent extensive introgression.
These results highlight a significant contribution of late post-mating barriers, such as chromosomal
divergence, for maintaining reproductive isolation, in an orchid group for which pre-mating barriers are often
considered predominant
CONVERGENZA DELL’IMPOLLINATORE ED ISOLAMENTO RIPRODUTTIVO IN SPECIE SIMPATRICHE DI OPHRYS (ORCHIDACEAE) IN SARDEGNA
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