Electrophysiological and behavioural responses of the housefly to “sweet” volatiles of the flowers of Caralluma europaea (Guss.) N.E. Br.

In sapromyiophilous plants, up to date, long range attraction of fly pollinators has been thoroughly investigated and attributed to “fetid” floral compounds, while the “sweet” floral scent fraction has not been specifically investigated and its role has received little attention. The aim of the present study was to verify if terpenoids, which are the main compounds of the floral bouquet of Caralluma europaea, play a role in the attraction of its pollinator Musca domestica. Terpinolene, α-terpinene and linalool, described as the three main volatiles of the flowers of C. europaea, were evaluated in electrophysiological investigations and blends of these compounds as well as the whole fresh flowers were used in behavioural assays. Antennae of housefly adults showed positive dose-dependent responses to all the chemicals tested. Houseflies were attracted by the odour of the fresh flowers and by the reconstructed terpenoid blend at the dose of 100 μg. At the dose of 10 μg, the blend did not produce any attraction. The results of the present study support the hypothesis that terpinolene, α-terpinene and linalool emitted by C. europaea flowers are involved in pollinator attraction and demonstrate the importance of the “sweet” scent in this sapromyiophilous species.     

Convergent evolution of carrion and faecal scent mimicry in fly-pollinated angiosperm flowers and a stinkhorn fungus

Flowers of many angiosperms attract fly pollinators through mimicry of animal carrion and faeces. This phenomenon of “sapromyiophily” is also evident in the sporophytes of some mosses and fruiting bodies of “stinkhorn” fungi, both of which use flies as agents of spore dispersal. We studied the scent chemistry of a stinkhorn fungus (Clathrus archeri) and seven fly-pollinated plant species with foetid odours to determine the degree to which these organisms mimic the scent of carrion and faeces (reference scent samples were collected from rotting meat, a rat carcass and horse and dog faeces), as well as the degree of convergent evolution between the fungus and angiosperm flowers. We found that scents of both the fungus and angiosperms tended to contain compounds typical of carrion, such as oligosulphides, and of faeces, such as phenol, indole and p-cresol. This study provides compelling new evidence for mimicry of carrion and faeces, as well as a striking pattern of convergence in the putrid scents of the fungus and the angiosperms, relative to those of confamilial species. The syndrome of sapromyiophily thus encompasses at least two kingdoms (Plantae and Fungi) and provides an effective means of exploiting flies as agents of pollen and spore dispersal.     

Can a stench be beautiful? – Osmophores in stem-succulent stapeliads (Apocynaceae-Asclepiadoideae-Ceropegieae-Stapeliinae)

Carrion flower stapeliads are examples of olfactory mimicry, forming sapromyiophilous flowers, which mimic food sources or oviposition sites to attract fly pollinators. The aim of this work was to investigate the ultrastructure of osmophores involved in the release of the carrion odor of Orbea variegata and Boucerosia indica flowers. In spite of their similar architecture (epidermal epithelium+subepidermal secretory layers), the osmophores of stapeliads feature some differences in morphology and ultrastructure. The epidermal epithelial cells of O. variegata and B. indica differ in shape, but both are extremely rich in endoplasmic reticulum and flocculent material in the vacuole. Unlike the Orbea, Boucerosia has starchless leucoplasts in the epidermal epithelium. Orbea features a cuticle with microchannels, while Boucerosia has a different mechanism for the pathway of scent substances to the cell exterior. They are released by rupturing of the outer layer of cuticle at the apex of the papillae. The epidermal cells of the adaxial corolla differ even between parts of the corolla, the corolla lobes and the annulus in the flower. This diversity may be connected with an odor gradient. The morphological and anatomical features of stapeliad (subtribe Stapeliinae) osmophores are generally similar to osmophores of members of subtribe Ceropegiinae (Ceropegia), thus, we suggest that this model of osmophores evolved before early diversification of Ceropegieae. The ultrastructural features of stapeliad osmophores are generally similar to those of Araceae, Orchidaceae and Passifloraceae.     

Floral biology and reproductive isolation by floral scent in three sympatric aroid species in French Guiana

We studied the reproductive biology of three sympatric Araceae species, Anthurium sagittatum, A. thrinax and Spathiphyllum humboldtii in French Guiana. The plants flowered simultaneously and were visited by scent‐collecting male euglossine bees, which were apparently their major pollinators. In total, each species was visited by 3–7 euglossine species, and 2–3 euglossine species accounted for at least 80% of all flower visits, with visits being plant species‐specific. Floral scent consisted of 6–10 main compounds, which made up 76–94% of the total amount of volatiles and were specific in these high amounts to each plant species. We suggest that the different floral scents lead to clear separation of the main pollinating euglossine species, providing a directed and efficient intraspecific pollen flow that results in high reproductive success. Since the simple floral (inflorescence) morphology of the studied plants does not support any morphological mechanisms to exclude visitors, as for example in euglossine‐pollinated perfume orchids, floral scent might be of major importance for the reproductive isolation and sympatric occurrence of these plants.     

Chemical mimicry of insect oviposition sites: a global analysis of convergence in angiosperms

Floral mimicry of decaying plant or animal material has evolved in many plant lineages and exploits, for the purpose of pollination, insects seeking oviposition sites. Existing studies suggest that volatile signals play a particularly important role in these mimicry systems. Here, we present the first large‐scale phylogenetically informed study of patterns of evolution in the volatile emissions of plants that mimic insect oviposition sites. Multivariate analyses showed strong convergent evolution, represented by distinct clusters in chemical phenotype space of plants that mimic animal carrion, decaying plant material, herbivore dung and omnivore/carnivore faeces respectively. These plants deploy universal infochemicals that serve as indicators for the main nutrients utilised by saprophagous, coprophagous and necrophagous insects. The emission of oligosulphide‐dominated volatile blends very similar to those emitted by carrion has evolved independently in at least five plant families (Annonaceae, Apocynaceae, Araceae, Orchidaceae and Rafflesiaceae) and characterises plants associated mainly with pollination by necrophagous flies and beetles.     

Qualitative and quantitative analyses of flower scent in Silene latifolia

The quantitative and qualitative variability in floral scent of 98 specimens of the dioecious species Silene latifolia belonging to 15 European and 19 North American populations was determined. Floral scent was collected from single flowers using dynamic headspace methods, and analysed by Micro-SPE and GC-MS methods. The flowers showed a nocturnal rhythm, and scent was emitted only at night. The amount of emitted volatiles varied greatly during the season, from 400 ng/flower/2 min in June to 50 ng/flower/2 min in August and September. The qualitative variability in the floral scent was high and different chemotypes, characterised by specific scent compounds, were found. Female and male flowers emitted the same type and amount of volatiles. The differences in floral scent composition between European and North American populations were small. Typical compounds were isoprenoids like lilac aldehyde isomers, or trans-beta-ocimene, and benzenoids like benzaldehyde, phenyl acetaldehyde, or veratrole. Some of these compounds are known to attract nocturnal Lepidoptera species. The high qualitative variability is discussed in relation to the pollination biology of S. latifolia, and the results are compared with other studies investigating intraspecific variability of flower scent.     

Smells like debauchery: The chemical composition of semen-like,sweat-like and faintly foetid floral odours in Xysmalobium (Apocynaceae: Asclepiadoideae)

Floral volatiles play an important role in plant communication with both pollinators and antagonists, but remain poorly explored for many plant groups. Asclepiads (Apocynaceae: Asclepiadoideae subtribe Asclepiadinae) represent a diverse group in South African grasslands, but the scents of most species remain unexplored and few genera are sufficiently sampled to allow comparisons between congeners. I used dynamic headspace extraction methods and coupled gas chromatography-mass spectrometry (GC–MS) to examine the scent chemistry of three unusually scented asclepiads in the genus Xysmalobium and then combined these data with previously published data to explore inter- and intraspecific variation in the genus. A total of 74 compounds (33–44 per species) from various compound classes were detected in the species examined here. The sweet but faintly foetid scent of Xysmalobium asperum was dominated by epoxy oxoisophorone in combination with various other terpenoids and aromatics, and small amounts of p-cresol. The sweat-like scent of Xysmalobium tysonianum was dominated by a few aromatics in combination with isovaleric acid and several aliphatic compounds normally associated with microbial degradation or fermentation. The semen-like scent of Xysmalobium parviflorum flowers examined here contained large relative amounts of 1-pyrroline, and comparison with previously published data for dung-scented flowers from a different population revealed clear divergence in the relative amounts of this compound and p-cresol. I also detected 25 compounds that were not shared between the two X. parviflorum populations. Comparison of scent data for eight Xysmalobium species revealed very distinct chemical profiles with limited overlap between species. These results are discussed in relation to the possible roles of these volatiles as pollinator attractants and the evolution of floral scents within the genus.     

Genetic dissection of scent metabolic profiles in diploid rose populations

The scent of flowers is a very important trait in ornamental roses in terms of both quantity and quality. In cut roses, scented varieties are a rare exception. Although metabolic profiling has identified more than 500 scent volatiles from rose flowers so far, nothing is known about the inheritance of scent in roses. Therefore, we analysed scent volatiles and molecular markers in diploid segregating populations. We resolved the patterns of inheritance of three volatiles (nerol, neryl acetate and geranyl acetate) into single Mendelian traits, and we mapped these as single or oligogenic traits in the rose genome. Three other volatiles (geraniol, β-citronellol and 2-phenylethanol) displayed quantitative variation in the progeny, and we mapped a total of six QTLs influencing the amounts of these volatiles onto the rose marker map. Because we included known scent related genes and newly generated ESTs for scent volatiles as markers, we were able to link scent related QTLs with putative candidate genes. Our results serve as a starting point for both more detailed analyses of complex scent biosynthetic pathways and the development of markers for marker-assisted breeding of scented rose varieties.     

Variation in scent emission among floral parts and inflorescence developmental stages in beetle-pollinated Protea species (Proteaceae)

Floral fragrances are an important component for pollinator attraction in beetle-pollinated flowers. Several genera in the Proteaceae contain beetle-pollinated species. However, there is no information on the floral scent chemistry of beetle-pollinated members of the family. In this paper we report on the spatial variation and differences between developmental stages in emission of inflorescence (flowerhead) volatiles of four South African Protea species (P. caffra, P. dracomontana, P. simplex, and P. welwitschii) that are pollinated by cetoniine beetles. The scents from different inflorescence parts (bracts, perianth, styles, and nectar) and from successive anthesis stages of whole inflorescences were sampled using dynamic headspace collection and identified using GC–MS. Although the four species shared many scent compounds, possibly reflecting their close phylogenetic relationships and common pollinators, they showed significant differences in overall scent composition due to various species-specific compounds, such as the unique tiglate esters found in the scent of P. welwitschii. The strongest emissions and largest number of volatiles, especially monoterpenes, were from inflorescences at full pollen dehiscence. Senescing inflorescences of two species and nectars of all species emitted proportionally high amounts of acetoin (3-hydroxy-2-butanone) and aromatic alcohols, typical fermentation products. As a consequence, the scent composition of nectar was much more similar among species than was the scent composition of other parts of the inflorescence. These results illustrate how the blends of compounds that make up the overall floral scent are a dynamic consequence of emissions from various plant parts.     

Flower Scent and Pollination in Selected Neotropical Palms

Abstract: The flower scents of 14 palm species were collected in the field in Ecuador and Puerto Rico by head-space adsorption and analysed by gas chromatography-mass spectrometry. Insect visitors were recorded in seven of the species in Ecuador. The floral scent of the different species was dominated by a variety of compounds, e.g., the fatty-acid derived 3-pentanone and the hydrocarbon series dodecane to pentadecane, the benzenoid compound 1,4-dimethoxybenzene, the isoprenoids ( E )-ocimene, myrcene, linalool, and ( E )-α-farnesene and the nitrogen-containing compound 2-methoxy- sec -butylpyrazine. Rather than mirroring the systematics of the studied palm species, the chemical composition of the floral scent reflected the pollination mode. The scent of beetle-pollinated species was characterized by large amounts of one or a few dominant compounds, whereas fly- and bee-pollinated species contained a mixture of several compounds in smaller total amounts. We suggest that specific scent compounds, as found in the beetle-pollinated species, have evolved as a response to pollinator preferences. The importance of olfactory cues in relation to visual cues is higher in beetle-pollinated species than in species pollinated by flies and bees.     

Floral scent in bird- and beetle-pollinated Protea species (Proteaceae): Chemistry,emission rates and function

Evolutionary shifts between pollination systems are often accompanied by modifications of floral traits, including olfactory cues. We investigated the implications of a shift from passerine bird to beetle pollination in Protea for floral scent chemistry, and also explored the functional significance of Protea scent for pollinator attraction. Using headspace sampling and gas chromatography–mass spectrometry, we found distinct differences in the emission rates and chemical composition of floral scents between eight bird- and four beetle-pollinated species. The amount of scent emitted from inflorescences of beetle-pollinated species was, on average, about 10-fold greater than that of bird-pollinated species. Floral scent of bird-pollinated species consists mainly of small amounts of “green-leaf volatiles” and benzenoid compounds, including benzaldehyde, anisole and benzyl alcohol. The floral scent of beetle-pollinated species is dominated by emissions of linalool, a wide variety of other monoterpenes and the benzenoid methyl benzoate, which imparts a fruity odour to the human nose. The number of compounds recorded in the scent of beetle-pollinated species was, on average, greater than in bird-pollinated species (45 versus 29 compounds, respectively). Choice experiments using a Y-maze showed that a primary pollinator of Protea species, the cetoniine beetle Atrichelaphinis tigrina, strongly preferred the scent of inflorescences of the beetle-pollinated Protea simplex over those of the bird-pollinated sympatric congener, Protea roupelliae. This study shows that a shift from passerine bird- to insect-pollination can be associated with marked up-regulation and compositional changes in floral scent emissions.     

Floral scent chemistry within the genus Linnaea (Caprifoliaceae)

‘Beauty bush’ and ‘twin flower’ are common names attributed to two well‐recognizable species belonging to the genus Linnaea (16 spp.) – L. amabilis and L. borealis – long admired by botanists and gardeners for their perfumed paired bell‐shaped flowers. In the present study, we investigated their floral scent compositions through gas chromatography – mass spectrometry (GC‐MS) analysis of dynamic headspace samples. Because the flowers of L. borealis in wild populations are fragrant both during the day and in the evening, circadian variation of scent emission was also assessed for this species. In total, 26 chemical compounds comprise the floral scent bouquets of L. amabilis and L. borealis, identified as monoterpenes (14), benzenoids and phenylpropanoids (5), aliphatics (3), sesquiterpenes (3) and irregular terpenes (1). Whereas monoterpenes, notably (‐)‐α‐ and β‐pinene, dominated the scent of L. amabilis (over 82% relative abundance), benzene derivates: 1,4 dimethoxybenzene, anisaldehyde, 2‐phenylethanol, benzaldehyde and nicotinaldehyde were exclusive to analysed headspace samples of L. borealis, accounting for 52% to 100% of their relative compositions, in three Swedish populations. A southwestern Finnish population was characterized by the four first mentioned benzenoid compounds and large amounts of (‐)‐α‐ and β‐pinenes plus two aliphatic substances. The scent compounds identified for both species are ubiquitous and may serve as generalist attractants/stimulants for a broad assortment of anthophilous insects. The basic work on the flower scent of L. amabilis and L. borealis should inspire studies of their pollination biology, primarily the behaviour‐guiding roles of the characteristic emitted volatiles.     

A sheep in wolf's clothing: do carrion and dung odours of flowers not only attract pollinators but also deter herbivores?

Carrion and dung odours of various flowers have traditionally been considered an adaptation for attracting the flies and beetles that pollinate them. While we accept the role of such odours in pollinator attraction, we propose that they may also have another, overlooked, anti‐herbivore defensive function. We suggest that such odours may deter mammalian herbivores, especially during the critical period of flowering. Carrion odour is a good predictor for two potential dangers to mammalian herbivores: (1) pathogenic microbes, (2) proximity of carnivores. Similarly, dung odour predicts faeces‐contaminated habitats that present high risks of parasitism. These are two new types of repulsive olfactory aposematic mimicry by plants: (1) olfactory feigning of carcass (thanatosis), a well‐known behavioural defensive strategy in animals, (2) olfactory mimicry of faeces, which also has a defensive visual parallel in animals.     

Character displacement in polyphenic tadpoles

Biologists have long known that closely related species are often phenotypically different where they occur together, but are indistinguishable where they occur alone. The causes of such character displacement are controversial, however. We used polyphenic spadefoot toad tadpoles (Spea bombifrons and S. multiplicata) to test the hypothesis that character displacement evolves to minimize competition for food. We also sought to evaluate the role of phenotypic plasticity in the mediation of competitive interactions between these species. Depending on their diet, individuals of both species develop into either a small-headed omnivore morph, which feeds mostly on detritus, or a large-headed carnivore morph, which specializes on shrimp. Laboratory experiments and surveys of natural ponds revealed that the two species were more dissimilar in their tendency to produce carnivores when they occurred together than when they occurred alone. This divergence in carnivore production was expressed as both character displacement (where S. multiplicata's propensity to produce carnivores was lower in sympatry than in allopatry) and as phenotypic plasticity (where S. multiplicata facultatively enhanced carnivore production in S. bombifrons, and S. bombifrons facultatively suppressed carnivore production in S. multiplicata). In separate experiments, we established that S. bombifrons (the species for which carnivore production was enhanced) was the superior competitor for shrimp. Conversely, S. multiplicata (the species for which carnivore production was suppressed and omnivore production enhanced) was the superior competitor for detritus. These results therefore demonstrate that selection to minimize competition for food can cause character displacement. They also suggest that both character displacement and phenotypic plasticity may mediate competitive interactions between species.     

Phylogenetic fragrance patterns in Nicotiana sections Alatae and Suaveolentes

We analyzed floral volatiles from eight tobacco species (Nicotiana; Solanaceae) including newly discovered Brazilian taxa (Nicotiana mutabilis and "Rastroensis") in section Alatae. Eighty-four compounds were found, including mono- and sesquiterpenoids, nitrogenous compounds, benzenoid and aliphatic alcohols, aldehydes and esters. Floral scent from recent accessions of Nicotiana alata, Nicotiana bonariensis and Nicotiana langsdorffii differed from previously published data, suggesting intraspecific variation in scent composition at the level of biosynthetic class. Newly discovered taxa in Alatae, like their relatives, emit large amounts of 1,8-cineole and smaller amounts of monoterpenes on a nocturnal rhythm, constituting a chemical synapomorphy for this lineage. Fragrance data from three species of Nicotiana sect. Suaveolentes, the sister group of Alatae, (two Australian species: N. cavicola, N. ingulba; one African species: N. africana), were compared to previously reported data from their close relative, N. suaveolens. Like N. suaveolens, N. cavicola and N. ingulba emit fragrances dominated by benzenoids and phenylpropanoids, whereas the flowers of N. africana lacked a distinct floral scent and instead emitted only small amounts of an aliphatic methyl ester from foliage. Interestingly, this ester also is emitted from foliage of N. longiflora and N. plumbaginifolia (both in section Alatae s.l.), which share a common ancestor with N. africana. This result, combined with the synapomorphic pattern of 1,8 cineole emission in Alatae s.s., suggests that phylogenetic signal explains a major component of fragrance composition among tobacco species in sections Alatae and Suaveolentes. At the intraspecific level, interpopulational scent variation is widespread in sect. Alatae, and may reflect edaphic specialization, introgression, local pollinator shifts, genetic drift or artificial selection in cultivation. Further studies with genetically and geographically well-defined populations are needed to distinguish between these possibilities.     

Emitted and endogenous floral scent compounds of Prunus mume and hybrids

Prunus mume is the only species of Prunus known to produce a strong floral fragrance. Most interspecific hybrids between P. mume and other species of Prunus lack the fragrance. The analysis of variations in emitted and endogenous compounds among genetically close cultivars is a powerful approach for revealing the mechanisms underlying floral scent emission. Compounds emitted by flowers from five cultivars were collected using the static headspace method, and endogenous compounds in the flowers were extracted with ethyl acetate. Samples were analysed quantitatively and qualitatively using gas chromatography-mass spectrometry. The result showed that benzenoids were the dominant compounds, of which benzyl acetate was the principal component contributing to the floral scent of P. mume. A clustering analysis of the floral volatiles from the different cultivars suggested that the scent traits of hybrids are related to the taxonomic relationship between their parents. The correlations between the amount of the endogenous and emitted compounds revealed that benzyl acetate had a stronger tendency to be volatile than the other compounds and the volatilisation rate of volatile compounds varied greatly among different cultivars. The importance of the biosynthetic pathway and the function of benzaldehyde are discussed.     

Variation in floral characters,particularly floral scent,in sapromyophilous Stemona species

Flowers or inflorescences often deploy various signals, including visual, olfactory, and gustatory cues, that can be detected by their pollinators. In many plants, these cues and their functions are poorly understood. Deciphering the interactions between floral cues and pollinators is crucial for analyzing the reproductive success of flowering plants. In this study, we examined the composition of the fetid floral scents produced by several Stemona species, including nine S. tuberosa populations from across China, using dynamic headspace adsorption, gas chromatography, and mass spectrometry techniques. We compared variations in floral phenotype, including floral longevity, nectar rewards, pollinator behavior, and flower length and color among the Stemona species. Of the 54 scent compounds identified, the major compounds include fetid dimethyl disulfide, dimethyl trisulfide, 1‐pyrroline, butyric acid, p‐cresol, isoamyl alcohol, and indole. We detected striking differentiation in floral scent at both the species and population level, and even within a population of plants with different colored flowers. Floral characteristics related to sapromyophily and deceptive pollination, including flower color mimicking livor mortis and a lack of nectar, were found in five Stemona species, indicating that Stemona is a typical sapromyophilous taxon. Species of this monocot genus might employ evolutionary tactics to exploit saprophilous flies for pollination.     

A novel pollination mode,saprocantharophily, in Duguetia cadaverica (Annonaceae): A stinkhorn (Phallales) flower mimic

Duguetia cadaverica (Annonaceae), a small understory tree of humid primary forest from the Guianas to Pará state, Brazil, unites several unusual blossom and floral characters such as flagelliflory and putrid-smelling flowers, respectively. The few pollination studies conducted in the large genus Duguetia have shown that species are usually cantharophilous, pollinated by either small (mostly Nitidulidae) or large specialized dynastid (Scarabaeidae) beetles. Foul-smelling flowers are a novelty within the genus, and to better understand their significance, we undertook a study of the reproductive biology and flower scent chemistry of D. cadaverica. In a primary forest of French Guiana, we observed and measured morphology and phenology of trees and flowers; additionally, flower pollination chamber temperature was measured and insect visitors to flowers observed. Flower scent was collected in situ and later analyzed in the laboratory by GC–MS. Flowers are visited by small beetles of a single Pycnocnemus species (Nitidulidae), which are the only insects observed to enter the pollination chamber. Moreover, flowers evince a rhythm in sexual stage, scent emission and temperature, which finds correspondence in behavioral characters of the putative nitidulid pollinator, such as timing of entry and exit from the pollination chamber. Floral scent analysis revealed an unusual, previously undescribed combination of chemical odor classes. The earthy, rank flower scent contained 18 compounds, among them fatty acid derivatives, terpenoids and N- and S-bearing compounds. The most abundant volatiles were 1-octen-3-ol, 3-octanone, and (E)-2-octenol, which are characteristic earthy odors of fungi; additionally, there were sulfides and 4-methylpentanoic acid, which are molecules associated with carcass and cheese odors, respectively.     

Temporal relationship between emitted and endogenous floral scent volatiles in summer‐ and winter‐blooming Jasminum species

Jasminum spp. is cultivated for their fragrant flowers used in essential oil production and cosmetic uses. An attempt was made to study the temporal variations in floral scent volatiles composition including emitted, free endogenous and glycosyl‐linked volatile compounds from two summer‐blooming species namely, Jasminum auriculatum and Jasminum grandiflorum as well as from two winter‐blooming species namely, Jasminum multiflorum and Jasminum malabaricum. The overall emitted volatile organic compounds (VOCs) were found to be highest when the matrix Porapak Q 80/100 was used with dichloromethane (DCM) as elution solvent. The floral volatile emission from bud to senescence exhibited nocturnal maxima pattern for both the summer‐blooming species. Both the winter‐blooming species emitted its highest concentration at noon. The free endogenous concentrations of all VOCs were low when corresponding emitted concentrations were high. Enzymatic treatment of petal extract revealed that several aromatic volatiles including aromatic alcohols and monoterpenols are synthesized and stored in the flowers as water‐soluble glycosides; these compounds were shown to accumulate in higher amounts in flowers at late bud stage. These findings indicate the utilization of the precursors, i.e. the volatile‐conjugates, through hydrolysis followed by their release as free‐volatiles at flower opening stage. The outcome as a whole suggests a linkage among the temporal pattern of emitted volatiles, free‐endogenous volatiles and glycoside‐bound volatile compounds in all above studied Jasminum spp. and provided an overview of their floral volatilome.     

Chemistry and geographic variation of floral scent in Yucca filamentosa (Agavaceae)

We identified volatiles from the floral headspace of Yucca filamentosa using gas chromatography and mass spectrometry and analyzed floral scent composition and variation among populations pollinated by different yucca moth species. Twenty-one scent compounds were repeatedly identified and most could be categorized into two major classes: (1) homoterpenes derived from the sesquiterpene alcohol nerolidol and (2) long chain aliphatic hydrocarbons. Two biosynthetic pathways are thus responsible for the majority of floral volatiles in Y. filamentosa. The homoterpene E-4,8-dimethylnona-1,3,7-triene, which is released systemically by higher plants upon herbivory, was the most abundant compound. Two di-oxygenated compounds not previously reported as floral compounds also were detected. No differentiation in floral scent was observed between populations pollinated by different yucca moths, nor was there any correlation between chemical distance and geographic distance among populations. The total release rate of volatiles differed significantly among populations, but not between populations with different pollinators. The combination of unique compounds and low variation in the fragrance blend may reflect highly selective attraction of obligate pollinators to flowers. The observed lack of differentiation in floral scent can putatively explain high moth-mediated gene flow among sites, but it does not explain conservation of odor composition across populations with different pollinators.