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Philipp M. Schlüter - One of the best experts on this subject based on the ideXlab platform.
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the complete plastid genomes of Ophrys iricolor and o sphegodes orchidaceae and comparative analyses with other orchids
PLOS ONE, 2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:Sexually deceptive orchids of the genus Ophrys may rapidly evolve by adaptation to pollinators. However, understanding of the genetic basis of potential changes and patterns of relationships is hampered by a lack of genomic information. We report the complete plastid genome sequences of Ophrys iricolor and O. sphegodes, representing the two most species-rich lineages of the genus Ophrys. Both plastomes are circular DNA molecules (146754 bp for O. sphegodes and 150177 bp for O. iricolor) with the typical quadripartite structure of plastid genomes and within the average size of photosynthetic orchids. 213 Simple Sequence Repeats (SSRs) (31.5% polymorphic between O. iricolor and O. sphegodes) were identified, with homopolymers and dipolymers as the most common repeat types. SSRs were mainly located in intergenic regions but SSRs located in coding regions were also found, mainly in ycf1 and rpoC2 genes. The Ophrys plastome is predicted to encode 107 distinct genes, 17 of which are completely duplicated in the Inverted Repeat regions. 83 and 87 putative RNA editing sites were detected in 25 plastid genes of the two Ophrys species, all occurring in the first or second codon position. Comparing the rate of nonsynonymous (dN) and synonymous (dS) substitutions, 24 genes (including rbcL and ycf1) display signature consistent with positive selection. When compared with other members of the orchid family, the Ophrys plastome has a complete set of 11 functional ndh plastid genes, with the exception of O. sphegodes that has a truncated ndhF gene. Comparative analysis showed a large co-linearity with other related Orchidinae. However, in contrast to O. iricolor and other Orchidinae, O. sphegodes has a shift of the junction between the Inverted Repeat and Small Single Copy regions associated with the loss of the partial duplicated gene ycf1 and the truncation of the ndhF gene. Data on relative genomic coverage and validation by PCR indicate the presence, with a different ratio, of the two plastome types (i.e. with and without ndhF deletion) in both Ophrys species, with a predominance of the deleted type in O. sphegodes. A search for this deleted plastid region in O. sphegodes nuclear genome shows that the deleted region is inserted in a retrotransposon nuclear sequence. The present study provides useful genomic tools for studying conservation and patterns of relationships of this rapidly radiating orchid genus.
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List of genes identified in the plastomes of Ophrys iricolor and Ophrys sphegodes.
2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:List of genes identified in the plastomes of Ophrys iricolor and Ophrys sphegodes.
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Comparison of two Ophrys plastid genomes.
2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:Comparison of two Ophrys plastid genomes.
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multiple shifts to different pollinators fuelled rapid diversification in sexually deceptive Ophrys orchids
New Phytologist, 2015Co-Authors: Donata Cafasso, Philipp M. Schlüter, Hendrik Breitkopf, Renske E Onstein, Salvatore CozzolinoAbstract:Episodes of rapid speciation provide unique insights into evolutionary processes underlying species radiations and patterns of biodiversity. Here we investigated the radiation of sexually deceptive bee orchids (Ophrys). Based on a time-calibrated phylogeny and by means of ancestral character reconstruction and divergence time estimation, we estimated the tempo and mode of this radiation within a state-dependent evolutionary framework. It appears that, in the Pleistocene, the evolution of Ophrys was marked by episodes of rapid diversification coinciding with shifts to different pollinator types: from wasps to Eucera bees to Andrena and other bees. An abrupt increase in net diversification rate was detected in three clades. Among these, two phylogenetically distant lineages switched from Eucera to Andrena and other bees in a parallel fashion and at about the same time in their evolutionary history. Lack of early radiation associated with the evolution of the key innovation of sexual deception suggests that Ophrys diversification was mainly driven by subsequent ecological opportunities provided by the exploitation of novel pollinator groups, encompassing many bee species slightly differing in their sex pheromone communication systems, and by spatiotemporal fluctuations in the pollinator mosaic.
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genic rather than genome wide differences between sexually deceptive Ophrys orchids with different pollinators
Molecular Ecology, 2014Co-Authors: Khalid E M Sedeek, Salvatore Cozzolino, Giovanni Scopece, Florian P Schiestl, Yannick M Staedler, Jurg Schonenberger, Philipp M. SchlüterAbstract:High pollinator specificity and the potential for simple genetic changes to affect pollinator attraction make sexually deceptive orchids an ideal system for the study of ecological speciation, in which change of flower odour is likely important. This study surveys reproductive barriers and differences in floral phenotypes in a group of four closely related, coflowering sympatric Ophrys species and uses a genotyping-by-sequencing (GBS) approach to obtain information on the proportion of the genome that is differentiated between species. Ophrys species were found to effectively lack postpollination barriers, but are strongly isolated by their different pollinators (floral isolation) and, to a smaller extent, by shifts in flowering time (temporal isolation). Although flower morphology and perhaps labellum coloration may contribute to floral isolation, reproductive barriers may largely be due to differences in flower odour chemistry. GBS revealed shared polymorphism throughout the Ophrys genome, with very little population structure between species. Genome scans for FST outliers identified few markers that are highly differentiated between species and repeatable in several populations. These genome scans also revealed highly differentiated polymorphisms in genes with putative involvement in floral odour production, including a previously identified candidate gene thought to be involved in the biosynthesis of pseudo-pheromones by the orchid flowers. Taken together, these data suggest that ecological speciation associated with different pollinators in sexually deceptive orchids has a genic rather than a genomic basis, placing these species at an early phase of genomic divergence within the 'speciation continuum'.
Hannes F Paulus - One of the best experts on this subject based on the ideXlab platform.
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Speciation, pattern recognition and the maximization of pollination: general questions and answers given by the reproductive biology of the orchid genus Ophrys
Journal of Comparative Physiology A, 2019Co-Authors: Hannes F PaulusAbstract:Pollination syndromes evolved under the reciprocal selection of pollinators and plants (coevolution). Here, the two main methods are reviewed which are applied to prove such selection. (i) The indirect method is a cross-lineage approach using phylogenetical trees to understand the phylogeny. Thus, features of single origin can be distinguished from those with multiple origins. Nearly all pollination modes originate in multiple evolutionary ways. (ii) The most frequent pollinators cause the strongest selection because they are responsible for the plant’s most successful reproduction. The European sexually deceptive orchid genus Ophrys provides an example of a more direct way to prove selection because the attraction of a pollinator is species specific. Most members of the genus have remarkably variable flowers. The variability of the signals given off by the flowers enables the deceived pollinator males to learn individual flower patterns. They thus avoid already visited Ophrys flowers, interpreting them as females rejecting them. As the males will not return to these individually recognizable flowers, the pollinators´ learning behavior causes cross-pollination and prevents the orchid’s self-pollination.
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species boundaries in the Ophrys iricolor group in tunisia do local endemics always matter
Plant Systematics and Evolution, 2016Co-Authors: Julia Gogler, Hannes F Paulus, Salvatore Cozzolino, Anis Zitari, Manfred AyasseAbstract:The potential high pollinator specificity and the mosaic of highly differentiated potential habitats in the Mediterranean have probably fueled species diversification in the sexually deceptive genus Ophrys. Several endemic species have been described whose taxonomic status remains questionable. By using a combination of morphological, chemical, behavioural and genetic analyses, we have investigated the taxonomic status of O. vallesiana, a presumed endemic species of the O. iricolor/eleonorae group in Tunisia. We have found that O. eleonorae and O. vallesiana produce similar odour bouquets, are attractive to the same pollinators, have overlapping flower morphology and are genetically indistinct. Thus, all experimental evidence supports the conclusion that, in spite of the observed morphological differences in plant height and flower number, the local endemic O. vallesiana clusters together with the widespread and co-occurring O. eleonorae. Concomitantly, our results exclude a putative origin of O. vallesiana as a hybrid taxon between O. eleonorae and O. gazella, even if hybridization between these two species can occur locally. Our study demonstrates the need for accurate and multidisciplinary investigations for the proper taxonomic delimitation of local endemics and highlights the complexity of the evolutionary dynamics in Ophrys species complexes.
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functional significance of labellum pattern variation in a sexually deceptive orchid Ophrys heldreichii evidence of individual signature learning effects
PLOS ONE, 2015Co-Authors: Kerstin Stejskal, Hannes F Paulus, Martin Streinzer, Adrian G Dyer, Johannes SpaetheAbstract:Mimicking female insects to attract male pollinators is an important strategy in sexually deceptive orchids of the genus Ophrys, and some species possess flowers with conspicuous labellum patterns. The function of the variation of the patterns remains unresolved, with suggestions that these enhance pollinator communication. We investigated the possible function of the labellum pattern in Ophrys heldreichii, an orchid species in which the conspicuous and complex labellum pattern contrasts with a dark background. The orchid is pollinated exclusively by males of the solitary bee, Eucera berlandi. Comparisons of labellum patterns revealed that patterns within inflorescences are more similar than those of other conspecific plants. Field observations showed that the males approach at a great speed and directly land on flowers, but after an unsuccessful copulation attempt, bees hover close and visually scan the labellum pattern for up to a minute. Learning experiments conducted with honeybees as an accessible model of bee vision demonstrated that labellum patterns of different plants can be reliably learnt; in contrast, patterns of flowers from the same inflorescence could not be discriminated. These results support the hypothesis that variable labellum patterns in O. heldreichii are involved in flower-pollinator communication which would likely help these plants to avoid geitonogamy.
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pollinators as prepollinating isolation factors evolution and speciation in Ophrys orcffldaceae
Israel journal of botany, 2013Co-Authors: Hannes F Paulus, Claudia GackAbstract:ABSTRACT The flowers of the Mediterranean genus Ophrys imitate important specific sexual releasing factors of aculeate hymenopteran females. They attract hymenopteran males who attempt to copulate with the labellum searching for females. During this “pseudocopulation,” the insects perform pollination. As this relation is highly specific, the pollinators serve as prepollinating isolation factors. This is illustrated by many examples. We consider it evident that specific pollinators have a strong selective effect on Ophrys flowers. By comparing the characters of the Ophrys flowers and of their pollinators, we try to bring an indirect proof of this hypothesis1. As a pollinator usually acts as a prepollinating isolation mechanism, speciation in Ophrys is always a consequence of a change in pollinator. We discuss some ideas about how speciation in Ophrys might have occurred and how the attraction and pollination modality of pseudocopulation developed during evolution.
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genetic patterns and pollination in Ophrys iricolor and o mesaritica orchidaceae sympatric evolution by pollinator shift
Botanical Journal of the Linnean Society, 2009Co-Authors: Philipp M. Schlüter, Paulo Mauricio Ruas, Gudrun Kohl, Claudete De Fatima Ruas, Tod F Stuessy, Hannes F PaulusAbstract:Ophrys iricolor and O. mesaritica are a pair of morphologically similar, closely related sexually deceptive orchids from the eastern Mediterranean. Ophrys iricolor is known to be pollinated by Andrena morio males and the specific pollinator of Ophrys mesaritica is determined as Andrena nigroaenea. Amplified fragment length polymorphism revealed O. iricolor and O. mesaritica to be genetically intermixed on the whole, although populations of O. iricolor and O. mesaritica in geographical proximity are strongly differentiated, suggesting that specific pollinators locally differentiate these taxa. Based on the available biological data and the system of pollinator attraction operative in Ophrys, we hypothesize that O. mesaritica may have arisen from O. iricolor by pollinator shift and that this is more probable than scenarios invoking hybridization as a result of mispollination by rare, non-specific flower visitors or specifically attracted insects.
Salvatore Cozzolino - One of the best experts on this subject based on the ideXlab platform.
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the complete plastid genomes of Ophrys iricolor and o sphegodes orchidaceae and comparative analyses with other orchids
PLOS ONE, 2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:Sexually deceptive orchids of the genus Ophrys may rapidly evolve by adaptation to pollinators. However, understanding of the genetic basis of potential changes and patterns of relationships is hampered by a lack of genomic information. We report the complete plastid genome sequences of Ophrys iricolor and O. sphegodes, representing the two most species-rich lineages of the genus Ophrys. Both plastomes are circular DNA molecules (146754 bp for O. sphegodes and 150177 bp for O. iricolor) with the typical quadripartite structure of plastid genomes and within the average size of photosynthetic orchids. 213 Simple Sequence Repeats (SSRs) (31.5% polymorphic between O. iricolor and O. sphegodes) were identified, with homopolymers and dipolymers as the most common repeat types. SSRs were mainly located in intergenic regions but SSRs located in coding regions were also found, mainly in ycf1 and rpoC2 genes. The Ophrys plastome is predicted to encode 107 distinct genes, 17 of which are completely duplicated in the Inverted Repeat regions. 83 and 87 putative RNA editing sites were detected in 25 plastid genes of the two Ophrys species, all occurring in the first or second codon position. Comparing the rate of nonsynonymous (dN) and synonymous (dS) substitutions, 24 genes (including rbcL and ycf1) display signature consistent with positive selection. When compared with other members of the orchid family, the Ophrys plastome has a complete set of 11 functional ndh plastid genes, with the exception of O. sphegodes that has a truncated ndhF gene. Comparative analysis showed a large co-linearity with other related Orchidinae. However, in contrast to O. iricolor and other Orchidinae, O. sphegodes has a shift of the junction between the Inverted Repeat and Small Single Copy regions associated with the loss of the partial duplicated gene ycf1 and the truncation of the ndhF gene. Data on relative genomic coverage and validation by PCR indicate the presence, with a different ratio, of the two plastome types (i.e. with and without ndhF deletion) in both Ophrys species, with a predominance of the deleted type in O. sphegodes. A search for this deleted plastid region in O. sphegodes nuclear genome shows that the deleted region is inserted in a retrotransposon nuclear sequence. The present study provides useful genomic tools for studying conservation and patterns of relationships of this rapidly radiating orchid genus.
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List of genes identified in the plastomes of Ophrys iricolor and Ophrys sphegodes.
2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:List of genes identified in the plastomes of Ophrys iricolor and Ophrys sphegodes.
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Comparison of two Ophrys plastid genomes.
2018Co-Authors: Luca Roma, Salvatore Cozzolino, Philipp M. Schlüter, Giovanni Scopece, Donata CafassoAbstract:Comparison of two Ophrys plastid genomes.
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species boundaries in the Ophrys iricolor group in tunisia do local endemics always matter
Plant Systematics and Evolution, 2016Co-Authors: Julia Gogler, Hannes F Paulus, Salvatore Cozzolino, Anis Zitari, Manfred AyasseAbstract:The potential high pollinator specificity and the mosaic of highly differentiated potential habitats in the Mediterranean have probably fueled species diversification in the sexually deceptive genus Ophrys. Several endemic species have been described whose taxonomic status remains questionable. By using a combination of morphological, chemical, behavioural and genetic analyses, we have investigated the taxonomic status of O. vallesiana, a presumed endemic species of the O. iricolor/eleonorae group in Tunisia. We have found that O. eleonorae and O. vallesiana produce similar odour bouquets, are attractive to the same pollinators, have overlapping flower morphology and are genetically indistinct. Thus, all experimental evidence supports the conclusion that, in spite of the observed morphological differences in plant height and flower number, the local endemic O. vallesiana clusters together with the widespread and co-occurring O. eleonorae. Concomitantly, our results exclude a putative origin of O. vallesiana as a hybrid taxon between O. eleonorae and O. gazella, even if hybridization between these two species can occur locally. Our study demonstrates the need for accurate and multidisciplinary investigations for the proper taxonomic delimitation of local endemics and highlights the complexity of the evolutionary dynamics in Ophrys species complexes.
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multiple shifts to different pollinators fuelled rapid diversification in sexually deceptive Ophrys orchids
New Phytologist, 2015Co-Authors: Donata Cafasso, Philipp M. Schlüter, Hendrik Breitkopf, Renske E Onstein, Salvatore CozzolinoAbstract:Episodes of rapid speciation provide unique insights into evolutionary processes underlying species radiations and patterns of biodiversity. Here we investigated the radiation of sexually deceptive bee orchids (Ophrys). Based on a time-calibrated phylogeny and by means of ancestral character reconstruction and divergence time estimation, we estimated the tempo and mode of this radiation within a state-dependent evolutionary framework. It appears that, in the Pleistocene, the evolution of Ophrys was marked by episodes of rapid diversification coinciding with shifts to different pollinator types: from wasps to Eucera bees to Andrena and other bees. An abrupt increase in net diversification rate was detected in three clades. Among these, two phylogenetically distant lineages switched from Eucera to Andrena and other bees in a parallel fashion and at about the same time in their evolutionary history. Lack of early radiation associated with the evolution of the key innovation of sexual deception suggests that Ophrys diversification was mainly driven by subsequent ecological opportunities provided by the exploitation of novel pollinator groups, encompassing many bee species slightly differing in their sex pheromone communication systems, and by spatiotemporal fluctuations in the pollinator mosaic.
Manfred Ayasse - One of the best experts on this subject based on the ideXlab platform.
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Sexual Deception in the Eucera-Pollinated Ophrys leochroma: A Chemical Intermediate between Wasp- and Andrena-Pollinated Species
Journal of Chemical Ecology, 2017Co-Authors: Monica Cuervo, Demetra Rakosy, Carlos Martel, Stefan Schulz, Manfred AyasseAbstract:Ophrys flowers mimic sex pheromones of attractive females of their pollinators and attract males, which attempt to copulate with the flower and thereby pollinate it. Virgin females and orchid flowers are known to use the same chemical compounds in order to attract males. The composition of the sex pheromone and its floral analogue, however, vary between pollinator genera. Wasp-pollinated Ophrys species attract their pollinators by using polar hydroxy acids, whereas Andrena -pollinated species use a mixture of non-polar hydrocarbons. The phylogeny of Ophrys shows that its evolution was marked by episodes of rapid diversification coinciding with shifts to different pollinator groups: from wasps to Eucera and consequently to Andrena and other bees. To gain further insights, we studied pollinator attraction in O. leochroma in the context of intra- and inter-generic pollinator shifts, radiation, and diversification in the genus Ophrys . Our model species, O. leochroma , is pollinated by Eucera kullenbergi males and lies in the phylogeny between the wasp and Andrena -pollinated species; therefore, it is a remarkable point to understand pollinator shifts. We collected surface extracts of attractive E. kullenbergi females and labellum extracts of O. leochroma and analyzed them by using gas chromatography with electroantennographic detection (GC-EAD) and gas chromatography coupled with mass spectrometry (GC-MS). We also performed field bioassays. Our results show that O. leochroma mimics the sex pheromone of its pollinator’s female by using aldehydes, alcohols, fatty acids, and non-polar compounds (hydrocarbons). Therefore, in terms of the chemistry of pollinator attraction, Eucera -pollinated Ophrys species might represent an intermediate stage between wasp- and Andrena -pollinated orchid species.
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species boundaries in the Ophrys iricolor group in tunisia do local endemics always matter
Plant Systematics and Evolution, 2016Co-Authors: Julia Gogler, Hannes F Paulus, Salvatore Cozzolino, Anis Zitari, Manfred AyasseAbstract:The potential high pollinator specificity and the mosaic of highly differentiated potential habitats in the Mediterranean have probably fueled species diversification in the sexually deceptive genus Ophrys. Several endemic species have been described whose taxonomic status remains questionable. By using a combination of morphological, chemical, behavioural and genetic analyses, we have investigated the taxonomic status of O. vallesiana, a presumed endemic species of the O. iricolor/eleonorae group in Tunisia. We have found that O. eleonorae and O. vallesiana produce similar odour bouquets, are attractive to the same pollinators, have overlapping flower morphology and are genetically indistinct. Thus, all experimental evidence supports the conclusion that, in spite of the observed morphological differences in plant height and flower number, the local endemic O. vallesiana clusters together with the widespread and co-occurring O. eleonorae. Concomitantly, our results exclude a putative origin of O. vallesiana as a hybrid taxon between O. eleonorae and O. gazella, even if hybridization between these two species can occur locally. Our study demonstrates the need for accurate and multidisciplinary investigations for the proper taxonomic delimitation of local endemics and highlights the complexity of the evolutionary dynamics in Ophrys species complexes.
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pollinator driven speciation in sexually deceptive orchids of the genus Ophrys
2010Co-Authors: Manfred Ayasse, Johannes Stokl, Julia GoglerAbstract:Ophrys orchids mimic females of their pollinator species to attract male insects for pollination. Reproductive isolation is based on the specific attraction of males of usually a single pollinator species, mostly bees, by mimicking the female species-specific sex-pheromone. Sexually deceptive orchids are ideal candidates for studies of sympatric speciation, because key adaptive traits such as the pollinator-attracting scent are associated with their reproductive success and with premating isolation.
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comparison of the flower scent of the sexually deceptive orchid Ophrys iricolor and the female sex pheromone of its pollinator andrena morio
Chemoecology, 2007Co-Authors: Johannes Stokl, Wittko Francke, Robert Twele, Dirk Erdmann, Manfred AyasseAbstract:Ophrys flowers mimic the female produced sex pheromone of their pollinator species to attract males for pollination. The males try to copulate with the putative female and thereby pollinate the flower. Using electrophysiological and chemical analyses, floral volatiles released by O. iricolor as well as the female sex pheromone of its pollinator species, Andrena morio are investigated. Overall, 38 peaks comprising 41 chemical compounds, were found to release reactions in the antennae of male A. morio bees. Analyses using coupled gas chromatography-mass spectrometry revealed the presence of alkanes and alkenes with 20 to 29 carbon atoms, aldehydes (C9 to C24) and two esters. Almost all of those compounds were found in similar proportions in both, the floral extracts of O. iricolor and cuticle surface extracts of A. morio females. The pattern of biologically active volatiles described here is very similar to that used by other Ophrys species pollinated by Andrena males.
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pollinator attracting odour signals in sexually deceptive orchids of the Ophrys fusca group
Plant Systematics and Evolution, 2005Co-Authors: Manfred Ayasse, Hannes F Paulus, Wittko Francke, Johannes Stokl, Amots Dafni, Claudia SchulzAbstract:We investigated patterns of volatiles of several allopatric and sympatric species of the Ophrys fusca group and one species of the O. mammosa/sphegodes group pollinated by either Andrena nigroaenea or A. flavipes, using electrophysiology (gas chromatography coupled with electroantennography; GC-EAD) and chemical analyses. We found 52 GC-EAD active compounds, mainly saturated and unsaturated hydrocarbons with chain lengths of 21 to 31, aldehydes, an ester, and an acid. Based on the relative proportions of all GC-EAD active compounds, the investigated species were compared using various statistical methods (ANOVA, principle component analyses, discriminant function analyses and cluster analyses). Our results show that Ophrys species with the same pollinator – independent of their phylogenetic relationship–use the same volatiles for pollinator attraction. Differences between the species mainly involve different quantitative patterns of volatiles. Our results are in congruence with previous studies that showed different odour bouquets to be responsible for the specific attraction of different pollinators and that alkanes and alkenes are most important for pollinator attraction.
Hendrik Breitkopf - One of the best experts on this subject based on the ideXlab platform.
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multiple shifts to different pollinators fuelled rapid diversification in sexually deceptive Ophrys orchids
New Phytologist, 2015Co-Authors: Donata Cafasso, Philipp M. Schlüter, Hendrik Breitkopf, Renske E Onstein, Salvatore CozzolinoAbstract:Episodes of rapid speciation provide unique insights into evolutionary processes underlying species radiations and patterns of biodiversity. Here we investigated the radiation of sexually deceptive bee orchids (Ophrys). Based on a time-calibrated phylogeny and by means of ancestral character reconstruction and divergence time estimation, we estimated the tempo and mode of this radiation within a state-dependent evolutionary framework. It appears that, in the Pleistocene, the evolution of Ophrys was marked by episodes of rapid diversification coinciding with shifts to different pollinator types: from wasps to Eucera bees to Andrena and other bees. An abrupt increase in net diversification rate was detected in three clades. Among these, two phylogenetically distant lineages switched from Eucera to Andrena and other bees in a parallel fashion and at about the same time in their evolutionary history. Lack of early radiation associated with the evolution of the key innovation of sexual deception suggests that Ophrys diversification was mainly driven by subsequent ecological opportunities provided by the exploitation of novel pollinator groups, encompassing many bee species slightly differing in their sex pheromone communication systems, and by spatiotemporal fluctuations in the pollinator mosaic.
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pollinator shifts between Ophrys sphegodes populations might adaptation to different pollinators drive population divergence
Journal of Evolutionary Biology, 2013Co-Authors: Salvatore Cozzolino, Philipp M. Schlüter, Hendrik Breitkopf, Florian P Schiestl, Giovanni ScopeceAbstract:Local adaptation to different pollinators is considered one of the possible initial stages of ecological speciation as reproductive isolation is a by-product of the divergence in pollination systems. However, pollinator-mediated divergent selection will not necessarily result in complete reproductive isolation, because incipient speciation is often overcome by gene flow. We investigated the potential of pollinator shift in the sexually deceptive orchids Ophrys sphegodes and Ophrys exaltata and compared the levels of floral isolation vs. genetic distance among populations with contrasting predominant pollinators. We analysed floral hydrocarbons as a proxy for floral divergence between populations. Floral adoption of pollinators and their fidelity was tested using pollinator choice experiments. Interpopulation gene flow and population differentiation levels were estimated using AFLP markers. The Tyrrhenian O. sphegodes population preferentially attracted the pollinator bee Andrena bimaculata, whereas the Adriatic O. sphegodes population exclusively attracted A. nigroaenea. Significant differences in scent component proportions were identified in O. sphegodes populations that attracted different preferred pollinators. High interpopulation gene flow was detected, but populations were genetically structured at species level. The high interpopulation gene flow levels independent of preferred pollinators suggest that local adaptation to different pollinators has not (yet) generated detectable genome-wide separation. Alternatively, despite extensive gene flow, few genes underlying floral isolation remain differentiated as a consequence of divergent selection. Different pollination ecotypes in O. sphegodes might represent a local selective response imposed by temporal variation in a geographical mosaic of pollinators as a consequence of the frequent disturbance regimes typical of Ophrys habitats.
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floral isolation is the main reproductive barrier among closely related sexually deceptive orchids
Evolution, 2011Co-Authors: Philipp M. Schlüter, Salvatore Cozzolino, Giovanni Scopece, Hendrik Breitkopf, Karin Gross, Florian P SchiestlAbstract:Floral isolation is an important component of pollinator-driven speciation. However, up to now, only a few studies have quantified its strength and relative contribution to total reproductive isolation. In this study, we quantified floral isolation among three closely related, sympatric orchid species of the genus Ophrys by directly tracking pollen flow. Ophrys orchids mimic their pollinators' mating signals, and are pollinated by male insects during mating attempts. This pollination system, called sexual deception, is usually highly specific. However, whether pollinator specialization also conveys floral isolation is currently under debate. In this study, we found strong floral isolation: among 46 tracked pollen transfers in two flowering seasons, all occurred within species. Accounting for observation error rate, we estimated a floral isolation index ≥0.98 among each pair of species. Hand pollination experiments suggested that postpollination barriers were effectively absent among our study species. Genetic analysis based on AFLP markers showed a clear species clustering and very few F(1) hybrids in natural populations, providing independent evidence that strong floral isolation prevents significant interspecies gene flow. Our results provide the first direct evidence that floral isolation acts as the main reproductive barrier among closely related plant species with specialized pollination.