Non-host plant odor (Tanacetum vulgare; Asteracea) affects the reproductive behavior ofLobesia botrana Den. et Schiff (Lepidoptera: Tortricidae)

Females ofLobesia botrana Den. et Schiff. (Lepidoptera Tortricidae) are attracted in natural conditions by volatiles released by a nonhost plant: tansy (Tanacetum vulgare L.; Asteracea). We have shown that both tansy flowers and their odor inhibit oviposition behavior and mating behavior and reduce adult longevity. The mean number of eggs laid per female isolated with tansy flowers was reduced by up to 50% every 2 days during the 6 days of exposure. This reduction was maintained after the tansy was removed. In the presence of tansy essential oil, the egg-laying reduction ranged from about 30 to 80% according to the odor concentration. The number of spermatophores found in females isolated with tansy flowers was also reduced twofold compared to the control treatment, indicating that the presence of tansy reduced mating activity. This mating activity is strongly reduced, by two-thirds, when adults face the highest dose of essential oil compared to controls. The number of eggs laid by the controls cannot be explained by the number of spermatophores. Therefore, the reduction in oviposition has been attributed to the presence of tansy flowers or to the tansy odor. Tansy flowers and tansy odor increased male mortality during the exposure (10% in the control, 50% in the tansy treatment, and up to 98% in the odor treatment). The highest rates of male mortality occurred during the 4- to 6-day period of exposure to flowers or odor. Repellence resulting in sustained locomotor activity is a possible cause of such a mortality. Female mortality was increased only in response to the highest dose of odor. This increase might be due to egg retention, and not directly to a plant effect. We discuss the effects of tansy flower odor on different patterns relative to the reproductive behavior ofL. botrana and, especially, on oviposition behavior in the ecological context of plant selection and polyphagy.     

Plant odour processing in the antennal lobe of male and female grapevine moths,Lobesia botrana (Lepidoptera: Tortricidae)

Moths of Lobesia botrana (Lepidoptera: Tortricidae) are confronted with different volatiles emitted from the host plant during the different seasons. To test the hypothesis of plasticity of central plant odour processing in moths of different generations in the future, we first investigated the responses of antennal lobe (AL) interneurons of laboratory-reared virgin and mated males and females. We used intracellular recording and staining techniques while stimulating the antenna with a range of host and non-host plant odours. The AL structure of L. botrana is similar to that found in other Lepidoptera species studied. The most frequent physiological responses for all types of moths were obtained with (E)-2-hexenal, and with thujyl alcohol and β-thujone, components of tansy, a behaviourally attractive non-host plant. Some broadly responding neurons were capable of distinguishing between different compounds through different response patterns (excitation/inhibition) and/or different dose-response characteristics. Response characteristics (response spectra, threshold and specificity) of neurons were similar, independent of sex or mating status of the moths. Significant differences between the groups were, however, found in the proportion of responding neurons for a few tested components.     

Differences in nutritional quality of parts of Vitis vinifera berries affect fitness of the European grapevine moth

The European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), is a major grapevine pest in Europe. The larva is polyphagous and able to develop on more than 25 plant species, several of them being more suitable than Vitaceae for the fitness of L. botrana. Larvae normally eat the pulp of the berry, but may also consume the seeds according to the development stage of the berry and the larval density per bunch. Understanding the effect on individual fitness of such feeding behaviour is important to assess how suitable the different berry tissues are for this insect. We offered to the larvae either entire berries, seeds, or pulp with skin of the variety Vitis vinifera cv. ‘Cabernet Sauvignon’ as larval food in order to assess several life history traits from egg hatching to adult death. Two control groups were raised on semisynthetic diets, offering a low (no plant material) or a higher (with corn flour) nutritive value medium. The larvae performed differently when fed on diets containing different parts of berries. The larvae fed on a diet containing grape berry seeds had a prolonged development time and showed higher mortality. The females emerging from these larvae had a lower fecundity and mating success than the females emerging from larvae fed on diets containing other parts of the berries. However, their longevity was greater in comparison to the other groups. We conclude that seeds of Cabernet Sauvignon are not toxic to larvae but affect the reproductive life history traits in L. botrana.     

Male and female Trybliographa rapae (Hymenoptera: Figitidae) behavioural responses to food plant, infested host plant and combined volatiles

Many parasitoids use volatiles produced by plants as important cues during their food and host search process. We investigated the attraction of the parasitic wasp Trybliographa rapae Westwood (Hymenoptera: Figitidae) to volatiles emitted from plants infested by the cabbage root fly Delia radicum L. (Diptera: Anthomyiidae), as well as to volatiles from a nectar food plant. Behavioural choice tests showed that male parasitoids were not attracted to any volatiles from plants infested by D. radicum or from nectar plants, while females showed clear attraction to both volatile sources. Young females were more attracted to combined volatiles of host and food plants over those from only the host plant, whereas older females showed no differences in attraction to the two odour sources. This suggests that intercropping attractive flowers with host plants could potentially be used to recruit newly emerged parasitoids from surrounding fields while older parasitoids invest more energy in host location than in additional food search. Volatiles from a whole infested plant were chosen over those emitted from separated above- and below-ground parts from infested plants. It is important to consider the availability of both energy and host resources for parasitoids when designing an eco-compatible management of a vegetable crop system.     

Pea plant volatiles guide host location behaviour in the pea moth

Identification of plant volatiles that attract mated insect females for oviposition can provide important information about plant–insect relationships that can be used to develop pest control strategies involving manipulation of the female host search. Our study represents a first step towards identifying volatiles that affect the host location behaviour of the pea moth Cydia nigricana. The behaviours of virgin and mated males and females were analysed in cage experiments testing a two-choice situation at close range and in wind tunnel experiments evaluating upwind orientation over a distance. In both experimental setups, flowering pea plants constituted the most attractive phenological stage for mated females, with 58 % landing on such plants in the wind tunnel. Testing headspace extracts of different phenological stages of pea and of detached pea buds and flowers in the wind tunnel, mated females showed the highest landing responses to volatiles during flower development (budding 42 % and flowering 56 %) and from detached buds (46 %) and flowers (66 %). Volatile compounds collected from the various phenological stages of pea were analysed by gas chromatography–mass spectrometry, and the antennal responses to these headspace collections were evaluated by gas chromatography–electroantennography. Ten antennally active compounds were identified, nine of which were present in the headspace extracts of the whole pea plants at all tested phenological stages and in detached buds and flowers. Overall, our results demonstrate a clear link between host plant phenology, the corresponding plant odour, and the behaviour of mated C. nigricana females.     

Development of a synthetic plant volatile-based attracticide for female noctuid moths. I. Potential sources of volatiles attractive to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

This paper is the first of a series which will describe the development of a synthetic plant volatile-based attracticide for noctuid moths. It discusses potential sources of volatiles attractive to the cotton bollworm, Helicoverpa armigera (Hübner), and an approach to the combination of these volatiles in synthetic blends. We screened a number of known host and non-host (for larval development) plants for attractiveness to unmated male and female moths of this species, using a two-choice olfactometer system. Out of 38 plants tested, 33 were significantly attractive to both sexes. There was a strong correlation between attractiveness of plants to males and females. The Australian natives, Angophora floribunda and several Eucalyptu s species were the most attractive plants. These plants have not been recorded either as larval or oviposition hosts of Helicoverpa spp., suggesting that attraction in the olfactometer might have been as nectar foraging rather than as oviposition sources. To identify potential compounds that might be useful in developing moth attractants, especially for females, collections of volatiles were made from plants that were attractive to moths in the olfactometer. Green leaf volatiles, floral volatiles, aromatic compounds, monoterpenes and sesquiterpenes were found. We propose an approach to developing synthetic attractants, here termed 'super-blending', in which compounds from all these classes, which are in common between attractive plants, might be combined in blends which do not mimic any particular attractive plant.     

Discrepancy in laboratory and field attraction of apple fruit moth Argyresthia conjugella to host plant volatiles

Abstract.  Apple fruit moth Argyresthia conjugella is a specialist seed predator of rowan Sorbus aucuparia . Large-scale synchronous fluctuation of seed production in rowan (i.e. named masting) drives the apple fruit moth to seek alternative host plants such as apple, during years when rowan berries are not available for oviposition. The role of plant volatile compounds in the attraction of gravid apple fruit moth females is studied in a laboratory wind tunnel. Volatiles from rowan branches with green berries stimulate female moths to fly upwind and to land at the odour source. By contrast, females are not attracted to rowan branches without green berries, and they are not attracted to apple, demonstrating that the chemical stimulus from rowan berries is required for attraction. Attraction to synthetic compounds identified from rowan, anethole and 2-phenyl ethanol confirms the role of plant volatiles in host finding. These two compounds, however, show a discrepant behavioural effect in wind tunnel and field tests. Field traps baited with 2-phenyl ethanol capture female moths but anethole does not produce significant captures. Wind tunnel tests produce the opposite results: moths fly upwind towards the anethole lure, whereas 2-phenyl ethanol is not attractive at all. Wind tunnel attraction to 2-phenyl ethanol is achieved by adding odour from a rowan branch without berries, which is not attractive on its own. This finding demonstrates that interaction with the background odour contributes to the behavioural effect of plant volatile stimuli in the field.     

A NO‐CHOICE WIND TUNNEL OLFACTOMETER SYSTEM FOR EVALUATING THE ATTRACTIVENESS OF PLANT VOLATILES TO ADULT HELICOVERPA ARMIGERA (HÜBNER) (LEPIDOPTERA:NOCTUIDAE) *

Abstract A bioassay system to evaluate adult cotton bollworm (CBW), Helicoverpa armigera, behavioral responses to plant volatiles was described. The system was comprised of a no‐choice olfactometer, a wind tunnel, and a wind tunnel room. The olfactometer was designed to provide for the testing and evaluation of volatiles from a variety of natural and synthetic sources. The behavioral responses in this system demonstrated that the volatiles of wilted leaves of Pterocarya stenoptera, Toona sinensis and Populus canadensis, the main materials of which poplar bundles were made, only could attract virgin females but not mated females and males. The volatiles emitted from fresh carrot and celery flowers did not exhibit significant attractiveness to both sexes of CBW. 0.1% phenylacetaldehyde showed significant attraction for virgin females and males. The biological significance of attraction of volatiles from these plants for CBW was discussed.     

Host plant volatiles induce oriented flight behaviour in male European grapevine moths, Lobesia botrana

The European grapevine moth Lobesia botrana relies on a female produced sex pheromone for long-distance mate finding. Grapevine moth males compete heavily during limited time windows for females. The aim of this study was to investigate the perception of host plant volatiles by grapevine moth males and whether such compounds elicit upwind oriented flights. We compared five host plant headspace extracts by means of gas chromatography linked electroantennogram (EAG) recording. We identified 12 common host plant volatiles (aliphatic esters, aldehydes, and alcohols, aromatic compounds and terpenes) that elicit EAG responses from grapevine moth males and that occur in at least three of the host plant volatile headspace extracts tested. Subsequently the behavioural response of grapevine moth males to four these compounds presented singly and in mixtures (1-hexanol, 1-octen-3-ol, (Z)-3-hexenyl acetate and (E)-β-caryophyllene) was recorded in a wind tunnel. Grapevine moth males engaged in upwind flights to all of four compounds when released singly at 10,000 pg/min and to all, except 1-octen-3-ol, when released at 100 pg/min. A blend of the four host plant volatiles released at 10,000 pg/min and mixed at a ratio based on the analysis of Vitis vinifera cv. Solaris volatile emissions attracted significantly more males than any single compound. Grapevine moth males perceive and respond to host plant volatiles at biologically relevant levels indicating that host plant volatiles figure as olfactory cues and that L. botrana males can discern places where the likelihood of encountering females is higher.     

Endophytes of Grapevine Flowers,Berries, and Seeds: Identification of Cultivable Bacteria,Comparison with Other Plant Parts,and Visualization of Niches of Colonization

Endophytic bacteria can colonize various plants and organs. However, endophytes colonizing plant reproductive organs have been rarely analyzed. In this study, endophytes colonizing flowers as well as berries and seeds of grapevine plants grown under natural conditions were investigated by cultivation as well as by fluorescence in situ hybridization. For comparison, bacteria were additionally isolated from other plant parts and the rhizosphere and characterized. Flowers, fruits, and seeds hosted various endophytic bacteria. Some taxa were specifically isolated from plant reproductive organs, whereas others were also detected in the rhizosphere, endorhiza or grape inflo/infructescence stalk at the flowering or berry harvest stage. Microscopic analysis by fluorescence in situ hybridization of resin-embedded samples confirmed the presence of the isolated taxa in plant reproductive organs and enabled us to localize them within the plant. Gammaproteobacteria (including Pseudomonas spp.) and Firmicutes (including Bacillus spp.) were visualized inside the epidermis and xylem of ovary and/or inside flower ovules. Firmicutes, mainly Bacillus spp. were additionally visualized inside berries, in the intercellular spaces of pulp cells and/or xylem of pulp, but also along some cell walls inside parts of seeds. Analysis of cultivable bacteria as well as microscopic results indicated that certain endophytic bacteria can colonize flowers, berries, or seeds. Our results also indicated that some specific taxa may not only derive from the root environment but also from other sources such as the anthosphere.     

Pollinator attraction to volatiles from virgin and pollinated host flowers in a yucca/moth obligate mutualism

The classic obligate pollination–seed consumption mutualism between yuccas and yucca moths has been thought to be mediated by chemical cues, but empirical data on pollinator attraction to host floral volatiles in this association have been lacking. Here we show that the scent from virgin flowers of the host Yucca glauca is sufficient to attract its obligate pollinator Tegeticula yuccasella in Y‐tube olfactometer tests. Interestingly, both sexes of moths were attracted to the scent stimulus. Because yucca moths mate inside host flowers, the attraction of both females and males to host floral volatiles is likely to increase encounter rates. In a second test, female moths did not discriminate between virgin and hand‐pollinated flowers, indicating no post‐pollination change in scent production by the host that would lead to a reduction in pollinator attraction and thereby limit exploitation of the available seeds in host flowers. However, other mechanisms that could stabilise the mutualism between T. yuccasella and its yucca hosts have already been documented, i.e. selective abortion of heavily infested flowers, and a female‐derived host‐marking pheromone. Headspace collection and GC–MS were used to identify the blend of floral volatiles emitted by Y. glauca, which was found to be very similar to those of two other allopatric capsular‐fruited species, Y. elata and Y. filamentosa, revealing strong conservation of this trait within Yucca section Chaenocarpa.     

Spatial fragrance patterns in flowers of Silene latifolia: Lilac compounds as olfactory nectar guides?

Floral odour can differ qualitatively and quantitatively between different parts of the flowers, and these spatial fragrance patterns within the flowers can be used by pollinators for orientation on flowers. Here we present results of spatial fragrance patterns within flowers of the dioecious Silene latifolia (Caryophyllaceae). Volatiles were collected and analysed using a highly sensitive dynamic headspace method, which allows dramatically reducing the sample time. From all flower parts, especially the petals and the anthophore emitted the typical flower volatiles of S. latifolia. However, compounds emitted from the petals differed from compounds emitted by the anthophore. The anthophore emitted the monoterpenoids lilac aldehydes and alcohols, whereas, all other typical scent compounds (e.g. benzoids, other monoterpenoids) were emitted by the petals. Lilac aldehydes are known to be behaviourally very attractive for noctuid moths, and they may serve as nectar guides in S. latifolia.     

Structural investigation of selective binding dynamics for the pheromone‐binding protein 1 of the grapevine moth,Lobesia botrana

The European grapevine moth, Lobesia botrana (Denis & Schiffermüller), is a serious pest in vineyards in North and South America. Mating disruption techniques have been used to control and monitor L. botrana on the basis of its sexual communication. This needs a well‐tuned olfactory system, in which it is believed that pheromone‐binding proteins (PBPs) are key players that transport pheromones in the antennae of moths. In this study, the selectivity of a PBP, named as LbotPBP1, was tested by fluorescence binding assays against 11 sex pheromone components and 6 host plant volatiles. In addition, its binding mechanism was predicted on the basis of structural analyses by molecular docking and complex and steered molecular dynamics (SMD). Our results indicate that LbotPBP1 binds selectively to sex pheromone components over certain host plant volatiles, according to both in vitro and in silico tests. Thus, chain length (14 carbon atoms) and functional groups (i.e., alcohol and ester) appear to be key features for stable binding. Likewise, residues such as Phe12, Phe36, and Phe118 could participate in unspecific binding processes, whilst Ser9, Ser56, and Trp114 could participate in the specific recognition and stabilization of sex pheromones instead of host plant volatiles. Moreover, our SMD approach supported 11‐dodecenyl acetate as the best ligand for LbotPBP1. Overall, the dynamics simulations, contact frequency analysis and SMD shed light on the binding mechanism of LbotPBP1 and could overcome the imprecision of molecular docking, supporting the in vitro binding assays. Finally, the role of LbotPBP1 in the chemical ecology of L. botrana is discussed.     

Concurrent modulation of neuronal and behavioural olfactory responses to sex and host plant cues in a male moth

Mating has profound effects on animal physiology and behaviour, not only in females but also in males, which we show here for olfactory responses. In cotton leafworm moths, Spodoptera littoralis, odour-mediated attraction to sex pheromone and plant volatiles are modulated after mating, producing a behavioural response that matches the physiological condition of the male insect. Unmated males are attracted by upwind flight to sex pheromone released by calling females, as well as to volatiles of lilac flowers and green leaves of the host plant cotton, signalling adult food and mating sites, respectively. Mating temporarily abolishes male attraction to females and host plant odour, but does not diminish attraction to flowers. This behavioural modulation is correlated with a response modulation in the olfactory system, as shown by electro-physiological recordings from antennae and by functional imaging of the antennal lobe, using natural odours and synthetic compounds. An effect of mating on the olfactory responses to pheromone and cotton plant volatiles but not to lilac flowers indicates the presence of functionally independent neural circuits within the olfactory system. Our results indicate that these circuits interconnect and weigh perception of social and habitat odour signals to generate appropriate behavioural responses according to mating state.     

Development of a synthetic plant volatile-based attracticide for female noctuid moths. II. Bioassays of synthetic plant volatiles as attractants for the adults of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

This paper reports olfactometer studies to determine the attractiveness of synthetic equivalents of plant volatiles to Helicoverpa armigera (Hübner) moths. Synthetic volatiles identified from host plants and other volatiles reported in literature as attractants to various noctuid species were tested in a two-choice olfactometer. Of 34 single chemicals tested, only seven were significantly attractive, and six were significantly repellent. However, when presented as blends of two or more volatiles, 21 of 31 blends tested were significantly attractive, and only one was significantly repellent. The most attractive blends were those containing four to six components, including aromatic volatiles primarily found in flowers, especially 2-phenylethanol and phenylacetaldehyde and volatiles found primarily in leaves, including green leaf volatiles and terpenoids. Some general principles in blending volatiles for developing attracticides for H. armigera are presented, including the need for blend complexity, the combination of volatiles from leaves and flowers, and early consideration of pragmatic factors such as price and toxicological profile.     

Adjusting the scent ratio: using genetically modified Vitis vinifera plants to manipulate European grapevine moth behaviour

Herbivorous insects use olfactory cues to locate their host plant within a complex olfactory landscape. One such example is the European grapevine moth Lobesia botrana, a key pest of the grape in the Palearctic region, which recently expanded both its geographical and host plant range. Previous studies have showed that a synthetic blend of the three terpenoids, (E)‐β‐caryophyllene, (E)‐β‐farnesene and (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT), was as attractive for the moth as the complete grape odour profile in laboratory conditions. The same studies also showed that the specific ratio of these compounds in the grape bouquet was crucial because a percentage variation in any of the three volatiles resulted in almost complete inhibition of the blend's attractiveness. Here, we report on the creation of stable grapevine transgenic lines, with modified (E)‐β‐caryophyllene and (E)‐β‐farnesene emission and thus with an altered ratio compared to the original plants. When headspace collections from these plants were tested in wind tunnel behavioural assays, they were less attractive than control extracts. This result was confirmed by testing synthetic blends imitating the ratio found on natural and transformed plants, as well as by testing the plants themselves. With this evidence, we suggest that a strategy based on volatile ratio modification may also interfere with the host‐finding behaviour of L. botrana in the field, creating avenues for new pest control methods.     

Unexpected reactions of a generalist predator towards defensive devices of cassidine larvae (Coleoptera, Chrysomelidae)

Studies of multitrophic interactions show that insect faeces may act as a defensive device against predators, as kairomone source for attraction of antagonists and as a significant energy source for micro-organisms. In the present study, we investigated effects of larval faeces from leaf beetles of the subfamiliy Cassidinae towards a generalist predator, the ant Myrmica rubra. Most cassidine larvae collect their faeces together with exuviae as so-called abdominal defensive shields on two movable spines at the posterior tip. The effects of these abdominal shields towards M. rubra were studied in three cassidine species, which feed mono- or oligophagously upon tansy (Chrysanthemum vulgare): Cassida denticollis and C. sanguinosa which possess such faecal shields and, for comparison, C. stigmatica with shields made of exuviae only (=skin shield). Bioassays revealed that larvae with both faecal and skin shields were attacked by the ant M. rubra more often than larvae whose shields had been removed. This attractiveness of shields towards ants contrasts with other studies, which found that abdominal shields of chrysomelid larvae act as defensive mechanisms against generalist predators like ants. To characterize the attractive cues of the shields, we studied possible chemical and physical stimuli. Olfactometer bioassays with M. rubra and chemical analyses revealed that plant-derived volatiles from faecal shields of C. denticollis attracted the ant, whereas odour from skin shields of C. stigmatica did not. Skin shields also emitted volatiles which derived from tansy, but in much lower quantities. Exclusion of contact to surface chemicals of a faecal shield reduced the ants' aggressive behaviour, whereas a change in the moisture content of a faecal shield had no influence. Visual stimuli cannot be ruled out as enhancing the ants' reaction towards faecal shields with their attractive volatiles, and are suggested to play a major role in the ants' response towards skin shields. This novel attractive effect of the abdominal shields of cassidine larvae is discussed, especially with respect to host plant chemistry and possible functions of the shields that might outweigh the negative consequences of the attraction of the predator M. rubra. Received: 22 June 1998 / Accepted: 2 November 1998     

Floral color change and the attraction of insect pollinators in lungwort (Pulmonaria collina)

We studied the effect of floral color change on long- and short-distance attraction of insect pollinators to the herb lungwort, Pulmonaria collina. Lungwort flowers change color with age from red to blue. Young red flowers had a significantly greater pollen and nectar reward and were significantly more often unpollinated than old blue ones. Red and blue flowers both influenced long-distance attractiveness of plants, defined as the number of insect approaches towards an individual plant. After reaching a plant, flower visitors preferred to visit young red flowers. Therefore, short-distance attractiveness, defined as the number of flowers visited successively on an individual plant, was influenced mainly by the number of young red flowers. The co-occurrence of the change in reproductive ability, in amount of reward, and in flower color enabled lungwort plants to direct pollinators to reproductive, highly rewarding red flowers. The data suggest that by maintaining changed flowers lungwort plants can increase their long-distance attraction and simultaneously enhance the probability of flower visits to pre-changed flowers. Thus, we propose floral color change as a mechanism that can increase the efficiency of pollen transfer to enhance plant fitness. Received: 2 November 1998 / Accepted: 14 July 1999     

Floral display, pollinator visitation and reproductive success in the dioecious perennial herb Wurmbea dioica (Liliaceae)

Floral traits that increase attractiveness to pollinators are predicted to evolve through selection on male function rather than on female function. To determine the importance of male-biased selection in dioecious Wurmbea dioica, we examined sexual dimorphism in flower size and number and the effects of these traits on pollinator visitation and reproductive success of male and female plants. Males produced more and larger flowers than did females. Bees and butterflies responded to this dimorphism and visited males more frequently than females, although flies did not differentiate between the sexes. Within sexes, insect pollinators made more visits to and visited more flowers on plants with many flowers. However, visits per flower did not vary with flower number, indicating that visitation was proportional to the number of flowers per plant. When flower number was experimentally held constant, visitation increased with flower size under sunny but not overcast conditions. Flower size but not number affected pollen removal per flower in males and deposition in females. In males, pollen removal increased with flower size 3 days after flowers opened, but not after 6 days when 98% of pollen was removed. Males with larger flowers therefore, may have higher fitness not because pollen removal is more complete, but because pollen is removed more rapidly providing opportunities to pre-empt ovules. In females, pollen deposition increased with flower size 3 days but not 6 days after flowers opened. At both times, deposition exceeded ovule production by four-fold or more, and for 2 years seed production was not limited by pollen. Flower size had no effect on seed production per plant and was negatively related to percent seed set, implying a tradeoff between allocation to attraction and reproductive success. This indicates that larger flower size in females is unlikely to increase fitness. In both sexes, gamete production was positively correlated with flower size. In males, greater pollen production would increase the advantage of large flowers, but in females more ovules may represent a resource cost. Selection to increase flower size and number in W. dioica has probably occurred through male rather than female function. Received: 15 June 1997 / Accepted: 12 February 1998     

Factors affecting fruit and seed production of Paeonia ostii “Feng Dan”, an economically important oil tree

Many factors may affect reproduction of animal-pollinated species. In this study, the effects of pollen limitation, attractive traits (flower number, plant height and flower width) and flowering phenological traits (flowering onset, duration and synchrony) on female reproduction, as well as the patterns of variation in fruit and seed production within plants, were investigated in Paeonia ostii “Feng Dan” over two flowering seasons (2018 and 2019). Fruit set was very high (90%), and pollen supplementation did not increase fruit and seed production in either year, indicating no pollen limitation. Fruit set, ovule number per fruit and mean individual seed weight per fruit were not affected by any of the six attractive and phenological traits in either year, whereas seed number per fruit was related to the three attractive traits in one or both years. Seed number per plant was positively affected by the three attractive traits and best explained by flower number in both years, but the effect of each of the three phenological traits on seed number per plant differed between years. Within plants, the fruit set, ovule number, seed set and seed number per fruit declined from early- to late-opening flowers, presumably because of resource preemption, but the mean individual seed weight did not vary across the flowering sequence. Our study shows that attractive traits of Paeonia ostii “Feng Dan” are more important than flowering phenological traits in the prediction of total seed production per plant.