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Pollen presentation theory ( PPT) predicts that plant species typically pollinated by frequent and wasteful pollinators ought to be much more parsimonious and only gradually release pollen compared to plant species pollinated by infrequent pollinators that are efficient at delivering the pollen they remove. To test PPT, we compare the pollen presentation schedules and pollination systems in three related Epimedium species, having different pollinators. Results showed that differences in anther dehiscence and flowering traits resulted in different pollen packaging schedules. For E. sutchuenense and E. franchetii, a special 'roll-up' movement of the anther wall during anther dehiscence increased pollen removal compared to the dehiscence pattern in E. mikinorii, which lacked the 'roll-up' movement. Investigations revealed that honeybees had a higher pollen removal rate and lower stigmatic pollen load compared to bumblebees. In accordance with PPT, E. sutchuenense presents pollen sequentially and slowly for the frequent and wasteful honeybees. In comparison to E. sutchuenense, E. franchetii had a faster presentation rate and was adapted to the efficient and infrequent bumblebees. However, E. mikinorii was pollinated by both bumblebees and honeybees at high frequency and had the fastest pollen presentation. This pattern could reduce pollen wastage by honeybees and might be an adaptation to its short flower longevity (less than 1 day), to increase the chances of pollen deposition on stigmas. The study indicates that pollen presentation schedules can be a consequence of interactions among anther dehiscence, flowering traits and pollination environments for a given species. [ABSTRACT FROM AUTHOR]

Fragmentation of natural vegetation creates one of the largest threats to plant-pollinator interactions. Although fragmentation impacts on plant populations have been explored in many, mainly herbaceous, species, the response of wild mass-flowering species is poorly known. Here, we studied 28 heathland patches dominated by the mass-flowering shrub Rhododendron ferrugineum, each presenting different R. ferrugineum floral display sizes (total inflorescence number per patch) and patch isolation (median distance to the three nearest patches). We assessed the impacts of these two factors on (i) heathland patch visitor assemblage (considering R. ferrugineum versus surrounding community) and (ii) R. ferrugineum flower visitation rate and pollen transfer limitation (comparing seed set from emasculated to pollen-supplemented flowers). We found that diversity and abundance of bees visiting R. ferrugineum in heathland patches significantly decreased with decreasing R. ferrugineum floral display, while overall visitor density per patch and flower visitation rate increased. Moreover, a decrease in massive floral display and increase in patch isolation resulted in reduced visitor density in the surrounding community. Even in patches with few individuals, we found disproportionate visitor abundance in R. ferrugineum compared to the surrounding community. Finally, pollen transfer limitation in R. ferrugineum was neither affected by visitation rate nor by patch attributes. By disproportionally attracting pollinators from co-flowering species, and probably promoting geitonogamous pollen transfer, the mass-flowering trait appears adequate to compensate, in terms of conspecific pollen transfer, for the decrease in visitor diversity and abundance and in mate availability, which usually result from population fragmentation. [ABSTRACT FROM AUTHOR]

Background Most angiosperms present flowers in inflorescences, which play roles in reproduction, primarily related to pollination, beyond those served by individual flowers alone. An inflorescence's overall reproductive contribution depends primarily on the three-dimensional arrangement of the floral canopy and its dynamics during its flowering period. These features depend in turn on characteristics of the underlying branching structure (scaffold) that supports and supplies water and nutrients to the floral canopy. This scaffold is produced by developmental algorithms that are genetically specified and hormonally mediated. Thus, the extensive inflorescence diversity evident among angiosperms evolves through changes in the developmental programmes that specify scaffold characteristics, which in turn modify canopy features that promote reproductive performance in a particular pollination and mating environment. Nevertheless, developmental and ecological aspects of inflorescences have typically been studied independently, limiting comprehensive understanding of the relations between inflorescence form, reproductive function, and evolution. Scope This review fosters an integrated perspective on inflorescences by summarizing aspects of their development and pollination function that enable and guide inflorescence evolution and diversification. Conclusions The architecture of flowering inflorescences comprises three related components: topology (branching patterns, flower number), geometry (phyllotaxis, internode and pedicel lengths, three-dimensional flower arrangement) and phenology (flower opening rate and longevity, dichogamy). Genetic and developmental evidence reveals that these components are largely subject to quantitative control. Consequently, inflorescence evolution proceeds along a multidimensional continuum. Nevertheless, some combinations of topology, geometry and phenology are represented more commonly than others, because they serve reproductive function particularly effectively. For wind-pollinated species, these combinations often represent compromise solutions to the conflicting physical influences on pollen removal, transport and deposition. For animal-pollinated species, dominant selective influences include the conflicting benefits of large displays for attracting pollinators and of small displays for limiting among-flower self-pollination. The variety of architectural components that comprise inflorescences enable diverse resolutions of these conflicts. [ABSTRACT FROM AUTHOR]

Large floral displays receive more pollinator visits but involve higher production and maintenance costs. This can result in indirect costs which may negatively affect functions like reproductive output. In this study, we explored the relationship between floral display and indirect costs in two pairs of coflowering sympatric Mediterranean Cistus of contrasting flower size. We hypothesized that: (1) corolla production entails direct costs in dry mass, N and P, (2) corollas entail significant indirect costs in terms of fruit set and seed production, (3) indirect costs increase with floral display, (4) indirect costs are greater in larger-flowered sympatric species, and (5) local climatic conditions influence indirect costs. We compared fruit set and seed production of petal-removed flowers and unmanipulated control flowers and evaluated the influence of mean flower number and mean flower size on relative fruit and seed gain of petal-removed and control flowers. Fruit set and seed production were significantly higher in petal-removed flowers in all the studied species. A positive relationship was found between relative fruit gain and mean individual flower size within species. In one pair of species, fruit gain was higher in the large-flowered species, as was the correlation between fruit gain and mean number of open flowers. In the other pair, the correlation between fruit gain and mean flower size was also higher in the large-flowered species. These results reveal that Mediterranean environments impose significant constraints on floral display, counteracting advantages of large flowers from the pollination point of view with increased indirect costs of such flowers. [ABSTRACT FROM AUTHOR]

Investigating plant-pollinator interactions and pollen dispersal are particularly relevant for understanding processes ensuring long-term viability of fragmented plant populations. Pollen dispersal patterns may vary strongly, even between similar congeneric species, depending on the mating system, pollinator assemblages and floral traits. We investigated pollen dispersal and fruit production in a population of Vaccinium oxycoccos, an insect-pollinated shrub, and compared the pollen dispersal pattern with a co-flowering, sympatric congener, V. uliginosum. We examined whether they share pollinators (through interspecific fluorescent dye transfers) and may differently attract pollinators, by comparing their floral colour as perceived by insects. Fluorescent dyes were mainly dispersed over short distances (80% within 40.4 m (max. 94.5 m) for V. oxycoccos and 3.0 m (max. 141.3 m) for V. uliginosum). Dye dispersal in V. oxycoccos was not significantly affected by plant area, floral display or the proximity to V. uliginosum plants. Interspecific dye transfers were observed, indicating pollinator sharing. The significantly lower dye deposition on V. oxycoccos stigmas suggests lower visitation rates by pollinators, despite higher flower density and local abundance. The spectral reflectance analysis indicates that bees are unlikely to be able to discriminate between the two species based on floral colour alone. Fruit production increased with increasing floral display, but was not affected by proximity to V. uliginosum plants. Our study highlights that fragmented populations of V. oxycoccos, when sympatric with co-flowering V. uliginosum, might incur increased competition for the shared pollinators in the case of pollination disruption, which might then reduce outcrossed seed set. [ABSTRACT FROM AUTHOR]

Jatropha curcas L. (Euphorbiaceae) has attracted considerable recent attention as a potential horticultural crop based on the quality of its oil seed for biodiesel production, and its ability to grow in unproductive subtropical or subdesert soils. Additionally, several characteristics of the species make it a good model for a more thorough understanding of the reproductive biology of a species undergoing the domestication process. To date, there is limited information about its reproductive patterns and the genetics involved. Such information is necessary for developing efficient agronomic practices and for guiding the research needed to more fully understand the species' reproduction processes. J. curcas has an inconsistent mating system, which presents both opportunities and challenges in developing breeding strategies and agronomic practices. Unraveling the mating system of J. curcas can increase our understanding of the evolution of reproduction systems in monoecious plants. The influences of environmental factors on flowering and floral organ development have not been reported under either field or controlled conditions. Moreover, no genetic mechanisms controlling the characteristics of the flowering (architecture, sex expression and sex ratios) have been proposed. The present review assesses and synthesizes the current knowledge of the floral biology of J. curcas. It provides a description of the species, its reproductive organs and reproductive patterns, and discussing the factors influencing them. [ABSTRACT FROM AUTHOR]

The evolution of floral display is thought to be constrained by trade-offs between the size and number of flowers; however, empirical evidence for the trade-off is inconsistent. We examined evidence for trade-offs and hierarchical allocation of resources within and between two populations each of the monocarpic perennials, Cardiocrinum cordatum and C. giganteum. Within all populations, flower size-number trade-offs were evident after accounting for variation in plant size. In addition, variation in flower size explained much variation in flower-level allocation to attraction, and female and male function, a pattern consistent with hierarchical allocation. However, between population differences in flower size ( C. cordatum) and number ( C. giganteum) were not consistent with size-number trade-offs or hierarchical allocation. The population-level difference in C. cordatum likely reflects the combined influence of a time lag between initiation and maturation of flowers, and higher light levels in one population. Thus, our study highlights one mechanism that may account for the apparent independence of flower size and number in many studies. A prediction of sex allocation theory was also supported. In C. giganteum: plants from one population invested more mass in pistils and less in stamens than did plants from the other population. Detection of floral trade-offs in Cardiocrinum may be facilitated by monocarpic reproduction, production of a single inflorescence and ease of measuring plant size. [ABSTRACT FROM AUTHOR]

Floral traits that correlate with nectar availability or are linked functionally to nectar production carry the potential to enable remote assessment of energy rewards by pollinators. Such floral traits can be considered "honest" in the sense that they convey information about the quality or profitability of a lower to a pollinator. Recently a new sensory channel used in plant-pollinator interactions was identified. We demonstrated that evaporation of water from the nectar itself and the petals create local humidity gradients above Oenothera cespitosa (Onagraceae) lowers. Since these humidity gradients are directly linked to nectar volume, they convey reliable information about nectar rewards to hawkmoth pollinators (Sphingidae). Several studies document a variety of sensory cues that constitute honest signaling between plants and pollinators, and shed light on the central question of when the two parties should communicate honestly. In the following sections, I will comment on different honest signals mediating plant-pollinator interactions, with a special emphasis on our recent findings about floral humidity gradients. [ABSTRACT FROM AUTHOR]

Most research on plant-pollinator communication has focused on sensory and behavioral responses to relatively static cues. Floral rewards such as nectar, however, are dynamic, and foraging animals will increase their energetic profit if they can make use of floral cues that more accurately indicate nectar availability. Here we document such a cue-transient humidity gradients-using the night blooming flowers of Oenothera cespitosa (Onagraceae). The headspace of newly opened flowers reaches levels of about 4% above ambient relative humidity due to additive evapotranspira-tional water loss through petals and water-saturated air from the nectar tube. Floral humidity plumes differ from ambient levels only during the first 30 min after anthesis (before nectar is depleted in wild populations), whereas other floral traits (scent, shape, and color) persist for 12-24 h. Manipulative experiments indicated that floral humidity gradients are mechanistically linked to nectar volume and therefore contain information about energy rewards to floral visitors. Behavioral assays with Hyles lineata (Sphingidae) and artificial flowers with appropriate humidity gradients suggest that these hawkmoth pollinators distinguish between subtle differences in relative humidity when other floral cues are held constant. Moths consistently approached and probed flowers with elevated humidity over those with ambient humidity levels. Because floral humidity gradients are largely produced by the evaporation of nectar itself, they represent condition-informative cues that facilitate remote sensing of floral profitability by discriminating foragers. In a xeric environment, this level of honest communication should be adaptive when plant reproductive success is pollinator limited, due to intense competition for the attention of a specialized pollinator. [ABSTRACT FROM AUTHOR]

* Premise of the study: The showiness of floral displays is usually explained as an adaptation to attract pollinators. However, selection for less attractive displays imposed by non-pollinating agents, particularly herbivores, may balance pollinator-driven selection for highly visible inflorescences. We investigated whether inflorescence architecture, particularly the unusual groundlevel flowering associated with a specialized bird perch in Babiana ringens may have originated, in part, as an adaptive response to mammalian herbivory. * Methods: We measured levels of herbivory by antelope in populations of B. hirsuta , the putative sister species of B. ringens , which possesses the likely ancestral form of inflorescence architecture. To test for position-dependent effects of herbivory on flowers, we compared the herbivory rates and seed production of manipulated inflorescences in a field experiment. We predicted that flowers at the base of inflorescences would suffer less herbivory than those in apical positions. * Results: We found herbivore damage to flowers in 50% of naturally occurring B. hirsuta plants. Manipulated inflorescences with only basal flowers, and consequently similar infl orescence architecture to B. ringens , experienced significantly lower herbivory and higher seed set than inflorescences manipulated to have only apical flowers. * Conclusions: Our results are consistent with the hypothesis that position-dependent herbivory on inflorescences could have played a role in the evolution of inflorescence design. More specifically, position-dependent herbivory may have selected for the loss of apical flowers. Position-dependent herbivory may have contributed toward the evolution of a naked inflorescence axis, a structure that characterizes B. ringens and functions as a bird perch facilitating cross-pollination by sunbirds. [ABSTRACT FROM AUTHOR]

Heterogeneous distribution of resources in most plant populations results in a mosaic of plant physiological responses tending to maximize plant fitness. This includes plant responses to trophic interactions such as herbivory and mycorrhizal symbiosis which are concurrent in most plants. We explored fitness costs of 50% manual defoliation and mycorrhizal inoculation in Datura stramonium at different light availability and soil fertility environments in a greenhouse experiment. Overall, we showed that non-inoculated and mycorrhiza-inoculated plants did not suffer from 50% manual defoliation in all the tested combinations of light availability and soil fertility treatments, while soil nutrients and light availability predominately affected plant responses to the mycorrhizal inoculation. Fifty percent defoliation had a direct negative effect on reproductive traits whereas mycorrhiza-inoculated plants produced larger flowers than non-inoculated plants when light was not a limiting factor. Although D. stramonium is a facultative selfing species, other investigations had shown clear advantages of cross-pollination in this species; therefore, the effects of mycorrhizal inoculation on flower size observed in this study open new lines of inquiry for our understanding of plant responses to trophic interactions. Also in this study, we detected shifts in the limiting resources affecting plant responses to trophic interactions. [ABSTRACT FROM AUTHOR]

Abstract: Short growing seasons, low temperatures, and frequent strong wind classify high mountains as adverse environments, in which pollinator abundance and activity are reduced. In such environments, plants growing in dense stands comprising several species and thus exhibiting larger and more diverse flower displays may profit by attracting more visits from scarce alpine pollinators than do plants that grow alone or in patches only composed of conspecifics. To study whether aggregation of plants increases (facilitation) or decreases (competition) the attraction of pollinators, we measured the rate and numbers with which insects entered experimental plots in the Swiss Alps, and their behaviour at flowers in plots that they entered. The plots contained individuals of the blue-flowering cushion plant Eritrichium nanum, either alone or mixed with white- to yellowish-flowering Saxifraga species. Pollinators were generally rare: in 55% of 236 observation periods, no pollinators were observed. Over 95% of the pollinators were Diptera. The average probability of observing any insect at all was higher in plots that contained some Saxifraga flowers, including mixed plots, than in those containing only E. nanum flowers. However, although insects tended to choose Saxifraga as the first flower visited in mixed plots, in all other regards their visitation of Saxifraga and E. nanum flowers in such plots was statistically indistinguishable. We also detected no effect of floral neighbourhood on the frequencies of potentially geitonogamous visits or of transitions among individual plants of the same or different species. Thus, our study suggests that the presence of Saxifraga may facilitate visitation to E. nanum at larger spatial scales, but gives no evidence for either competition or facilitation at small scales within floral neighbourhoods. [Copyright &y& Elsevier]

Declines in availability of plant resources to pollinators are a major cause of pollinator loss. The management of plant communities to enhance floral resources is often proposed as a way to sustain pollinator populations. Nectar, the main energetic resource for pollinators, plays a central role in behaviour and composition of pollinator communities. Abiotic and biotic factors are known to influence nectar traits at both the species and community levels, but the impact of plant community composition itself has never been investigated. Below-ground interactions in plant communities can induce changes in plant development through (i) plant-derived litter amendment of the soil and (ii) competition for soil resources between plants. We tested how plant below-ground interactions affect above-ground nectar traits involved in plant attractiveness to pollinators. A short-term pot experiment was carried out with three temperate grassland species Mimulus guttatus, Lamium amplexicaule, and Medicago sativa, showing distinct litter stoichiometry and competitive abilities for soil resources. Litter amendment (none, mono and tri-specific litter) and plant interaction treatments (monocultures, two- and three-species mixtures) were crossed in a factorial design. Litter amendment to the soil led to an increase in total nectar sugar content in L. amplexicaule plants but not in the two other species. We also found that the presence of M. guttatus, a competitive species, reduced the total nectar sugar content in L. amplexicaule through a concomitant decrease in nectar volume per flower and in floral display size, but not in other species. Species-specific responses of nectar traits to variation in soil nitrogen availability were thus observed, suggesting consequences for plant species and community attractiveness to pollinators. However, we did not find evidence that the legume M. sativa affected nectar traits of any neighbouring plants. Synthesis. Our results demonstrate that litter inputs and competition between plants for soil resources can alter nectar traits linked to plant attractiveness to pollinators. This supports the idea that below-ground plant-plant interactions for soil resources can influence above-ground plant-plant interactions for pollination services. This offers promising perspectives in studying the role of below-ground-above-ground interactions on higher trophic levels. [ABSTRACT FROM AUTHOR]

A major gap in our understanding of floral evolution, especially micro-evolutionary processes, is the role of pollinators in generating patterns of natural selection on floral traits. Here we explicitly tested the role of pollinators in selecting floral traits in a herbaceous perennial, Penstemon digitalis., We manipulated the effect of pollinators on fitness through hand pollinations and compared phenotypic selection in open- and hand-pollinated plants., Despite the lack of pollen limitation in our population, pollinators mediated selection on floral size and floral display. Hand pollinations removed directional selection for larger flowers and stabilizing selection on flower number, suggesting that pollinators were the agents of selection on both of these traits., We reviewed studies that measured natural selection on floral traits by biotic agents and generally found stronger signatures of selection imposed by pollinators than by herbivores and co-flowering plant species. [ABSTRACT FROM AUTHOR]

We compared the floral morphologies, floral scents, and flower visitor compositions of Weigela coraeensis var. coraeensis on the Japanese mainland and its variety fragrans endemic to the Izu Islands to examine the differentiation process of W. coraeensis var. fragrans. The corolla lengths of W. coraeensis were smaller on the Izu Islands than those on the mainland and decreased gradually with the distance from the mainland, probably resulting from changes in pollinator fauna. A total of 13 volatile compounds were identified in the floral scent analyses, and limonene was produced at the highest level, although the floral scents were not different between var. coraeensis and var. fragrans. In this study, it was suggested that the pollinator fauna peculiar to the Izu Islands influenced the morphological differentiation of W. coraeensis var. fragrans. [ABSTRACT FROM AUTHOR]

Correlations between phenotypic traits are common in many organisms, but the relative importance of nonadaptive mechanisms and selection for the evolution and maintenance of such correlations are poorly understood. In polymorphic species, morphs may evolve quantitative differences in additional characters as a result of morph-specific selection. The perennial rosette herb Primula farinosa is polymorphic for scape length. The short-scaped morph is less damaged by grazers and seed predators but is more strongly pollen limited than the long-scaped morph. We examined whether morph-specific differences in biotic interactions are associated with differences in selection on two other traits affecting floral display (number of flowers and petal size) and on one trait likely to affect pollination efficiency (corolla tube width) in three P. farinosa populations. Differences in selection between morphs were detected in one population. In this population, selection for more flowers and larger petals was stronger in the short-scaped than in the long-scaped morph, and although there was selection for narrower corolla tubes in the short-scaped morph, no statistically significant selection on corolla tube width could be detected in the long-scaped morph. In the study populations, the short-scaped morph produced more and larger flowers and wider corolla tubes. Current morph-specific selection was thus only partly consistent with trait differences between morphs. The results provide evidence of morph-specific selection on traits associated with floral display and pollination efficiency, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Urban sprawl has led over wide areas to alteration and fragmentation of so many ecosystem types that it becomes essential to consider biodiversity conservation in urban planning. As the urbanisation is usually irreversible, the urban context has to be taken into account when defining appropriate management measures to sustain viable populations. Connectivity through pollen flow appears to be a key-factor for the long-term persistence of populations of insect-pollinated plant species. We investigated pollen dispersal using fluorescent dye as pollen analogue in Lychnis flos-cuculi, an insect-pollinated wetland herb, along the Woluwe River, in Brussels urban zone (Belgium). Dye dispersal showed an exponential decay distribution, with particles mainly deposited on neighbouring individuals and populations. The mean distance of dye transfer was 133.6m, with a maximal distance of 523.7m. Dye deposition was positively related to the number of potential recipient plants when distance to dye source was held constant. This may be associated with a higher flowering plant density across the flying distance that increases attractiveness and visitation rate of pollinators, and/or with secondary dye transfer. When connected, small and large populations only differed in response to the number of potential recipients. The small isolated population received little immigrant pollen flow, but remained a dye donor. Our study demonstrates that small populations of L. flos-cuculi along an urban river may still exchange pollen thanks to pollinator movements, and might therefore be regarded in management planning as potential connecting components between populations. [Copyright &y& Elsevier]

• Reduced allocation to structures for pollinator attraction is predicted in selfing species. We explored the association between outcrossing and floral display in a broad sample of angiosperms. We used the demonstrated relationship to test for bias against selfing species in the outcrossing rate distribution, the shape of which has relevance for the stability of mixed mating. • Relationships between outcrossing rate, flower size, flower number and floral display, measured as the product of flower size and number, were examined using phylogenetically independent contrasts. The distribution of floral displays among species in the outcrossing rate database was compared with that of a random sample of the same flora. • The outcrossing rate was positively associated with the product of flower size and number; individually, components of display were less strongly related to outcrossing. Compared with a random sample, species in the outcrossing rate database showed a deficit of small floral display sizes. • We found broad support for reduced allocation to attraction in selfing species. We suggest that covariation between mating systems and total allocation to attraction can explain the deviation from expected trade-offs between flower size and number. Our results suggest a bias against estimating outcrossing rates in the lower half of the distribution, but not specifically against highly selfing species. [ABSTRACT FROM AUTHOR]

Deceptive orchids are generally characterized by low levels of fruit set; however, there may be substantial variations in fruit set between sites and years. Within a single population, individual plants may also differ greatly in their reproductive output as a result of differences in inflorescence size or local density. In this study, we determined flower and fruit production over 5 years in two populations of the food-deceptive orchid, Orchis purpurea. All plants were monitored annually for survival and flowering at each site to determine whether flowering and fruiting induced costs. The number of flowers per inflorescence varied considerably from year to year (min: 36.6, max: 49.5). Average fruit set was low (7%) and varied considerably among years and populations. A considerable proportion of plants also failed to set any fruit. However, the probability of producing at least one fruit was not affected by inflorescence size or local density. The number of fruits was significantly related to inflorescence size, but proportional fruit set was not. Local density also did not affect the number of fruits, nor proportional fruit set. There was also no evidence that plants with large inflorescence size or high fruiting success had a larger probability of remaining vegetative the year after flowering than plants with small inflorescence size or low fruiting success. Our results suggest that pollinator-mediated selective forces on inflorescence size through female reproductive success alone are weak, most likely because of the low overall level of visitation and the resulting uncertainty of pollination at the individual level. Our results further demonstrate that investigation of patterns of fruit set over several years is needed to better understand the variability in female reproductive success that is typical of most plant–pollinator interactions. [ABSTRACT FROM AUTHOR]

1. The evolution of many floral traits is thought to have been shaped by pollinator-mediated selection for increased attractiveness or an improved mechanical fit of flowers to pollinators. Yet, few studies have examined experimentally the independent and interactive effects of different aspects of flower morphology on plant reproductive success. 2. In the orchid Platanthera bifolia, perianth size and spur length are positively correlated within and among populations. To test the hypothesis that pollination success and seed output increases with increasing perianth size and spur length, we manipulated the two traits in a factorial design in a long-spurred population of P. bifolia pollinated by long-tongued hawkmoths. Additionally, to determine whether differences in selfing rate can explain variation in fruit set and fruit size, we performed controlled self- and cross-pollination. 3. Plants with long spurs had more flowers pollinated, more pollen removed and produced more and larger fruits compared to plants with short spurs. In contrast, perianth size did not affect the pollination success or fruit production of P. bifolia. 4. Fruit production and fruit size did not differ among flowers pollinated with self- and cross pollen, respectively. This indicates that reduced pollen deposition rather than pollinator-mediated self-pollination caused the reduction in fruit set and fruit volume observed after shortening of the spur. 5. The results demonstrate that spur length, but not perianth size, is critical for reproductive success in P. bifolia, and suggest that among-population differentiation in perianth size may reflect a correlated response to selection on spur length. The results are consistent with the hypothesis that visual display is less important than other cues for the reproductive success of P. bifolia, and underscore the necessity to experimentally examine the functional significance of putatively adaptive traits. [ABSTRACT FROM AUTHOR]

Background and Aims: Adjacent flowers on Mimulus ringens floral displays often vary markedly in selfing rate. We hypothesized that this fine-scale variation in mating system reflects the tendency of bumble-bee pollinators to probe several flowers consecutively on multiflower displays. When a pollinator approaches a display, the first flower probed is likely to receive substantial outcross pollen. However, since pollen carryover in this species is limited, receipt of self pollen should increase rapidly for later flowers. Here the first direct experimental test of this hypothesis is described. [ABSTRACT FROM PUBLISHER]

The evolution of floral display and flowering time in animal-pollinated plants is commonly attributed to pollinator-mediated selection. Yet, the causes of selection on flowering phenology and traits contributing to floral display have rarely been tested experimentally in natural populations. We quantified phenotypic selection on morphological and phenological characters in the perennial, outcrossing herb Arabidopsis lyrata in two years using female reproductive success as a proxy of fitness. To determine whether selection on floral display and flowering phenology can be attributed to interactions with pollinators, selection was quantified both for open-pollinated controls and for plants receiving supplemental hand-pollination. We documented directional selection for many flowers, large petals, late start of flowering, and early end of flowering. Seed output was pollen-limited in both years and supplemental hand-pollination reduced the magnitude of selection on number of flowers, and reversed the direction of selection on end of flowering. The results demonstrate that interactions with pollinators may affect the strength of selection on floral display and the direction of selection on phenology of flowering in natural plant populations. They thus support the contention that pollinators can drive the evolution of both floral display and flowering time. [ABSTRACT FROM AUTHOR]

Spatio-temporal variation in seed predation may strongly influence both plant population dynamics and selection on plant traits. The intensity of seed predation may depend on a number of factors, but the relative importance of previous predator abundance (“local legacy”), spatial distribution of the host plant, environmental factors and plant characteristics has been explored in few species. We monitored seed predation in the perennial herb Primula farinosa, which is dimorphic for scape length, during 5 consecutive years, in a 10-km × 4-km area comprising 79 P. farinosa populations. A transplant experiment showed that the seed predator, the oligophagous tortricid moth Falseuncaria ruficiliana, was not dispersal limited at the spatial scale corresponding to typical distances between P. farinosa populations. Correlations between population characteristics and incidence and intensity of seed predation varied among years. The incidence of the seed predator was positively correlated with host population size and mean number of flowers, while intensity of seed predation in occupied patches was positively related to the frequency of the long-scaped morph in 2 years and negatively related to host population size in 1 year. In both scape morphs, predation tended to increase with increasing frequency of the long morph. There was no evidence of a local legacy; incidence and intensity of seed predation were not related to the abundance of the seed predator in the population in the previous year. Taken together, the results indicate that among-population variation in seed predation intensity is determined largely by patch selection and that the seed predator’s preference for tall and many-flowered inflorescences may not only affect selection on plant traits within host plant populations, but also the overall intensity of seed predation. [ABSTRACT FROM AUTHOR]

Florivores are antagonists that damage flowers, and have direct negative effects on flowering and pollination of the attacked plants. While florivory has mainly been studied for its consequences on seed production or siring success, little is known about its impact on mating systems. Damage to flowers can alter pollinator attraction to the plant and may therefore modify patterns of pollen transfer. However, the consequences of damage for mating systems can take two forms: a decrease in flower number reduces opportunities for intra-inflorescence pollen deposition (geitonogamy), which, in turn, may lead to a decrease in selfing; whereas a decrease in floral display may also reduce overall visitation and thus increase the chances of self-pollination via facilitated or autonomous autogamy. We investigated the effects of damage by a bud-clipping weevil ( Anthonomus signatus) in Fragaria virginiana in an experimental setting mimicking natural conditions. We found that increased damage led to an increase in selfing, a result consistent with the increased autogamy pathway. We discuss the implications of this finding and evaluate the generality of florivore-mediated mating system expression. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the level of reproductive success (RS) in natural and anthropogenic populations of generalist orchid Epipactis palustris and its dependence on flower structure and nectar composition, i.e., amino acids and sugars. We found that both pollinaria removal and female reproductive success were high and similar in all populations, despite differences in flower traits and nectar chemistry. Flower structures were weakly correlated with parameters of RS. Nectar traits were more important in shaping RS; although, we noted differentiated selection on nectar components in distinct populations. Individuals in natural populations produced nectar with a larger amount of sugars and amino acids. The sucrose to (fructose and glucose) ratio in natural populations was close to 1, while in anthropogenic ones, a clear domination of fructose and glucose was noted. Our results indicate that the flower traits and nectar composition of E. palustris reflect its generalist character and meet the requirements of a wide range of pollinators, differing according to body sizes, mouth apparatus, and dietary needs. Simultaneously, differentiation of nectar chemistry suggests a variation of pollinator assemblages in particular populations or domination of their some groups. To our knowledge, a comparison of nectar chemistry between natural and anthropogenic populations of orchids is reported for the first time in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Plant–pollinator interactions determine reproductive success for animal-pollinated species and, in the case of invasive plants, they are supposed to play an important role in invasive success. We compared the invasive Senecio inaequidens to its native congener S. jacobaea in terms of interactions with pollinators. Visitor guild, visitation rate, and seed set were compared over 3years in three sites in Belgium. Floral display (capitula number and arrangement) and phenology were quantified, and visiting insects were individually censused, i.e. number of visited capitula and time per visited capitulum. As expected from capitula resemblance, visitor guilds of both species were very similar (proportional similarity=0.94). Senecio inaequidens was visited by 33 species, versus 36 for S. jacobaea. For both species, main visitors were Diptera, especially Syrphidae, and Hymenoptera. Visitation rate averaged 0.13 visitor per capitulum per 10min for S. inaequidens against 0.08 for S. jacobaea. However, insects visited more capitula per plant on S. jacobaea, due to high capitula density (886m−2 versus 206m−2 for S. inaequidens), which is likely to increase self-pollen deposition considerably. Seed set of S. jacobaea was lower than that of S. inaequidens. We suggest that floral display is the major factor explaining the differences in insect visitation and seed set between the two Senecio species. [Copyright &y& Elsevier]

Background and Aims: Few studies have examined the dynamics of specialist plant–pollinator interactions at a geographical scale. This knowledge is crucial for a more general evolutionary and ecological understanding of specialized plant–pollinator systems. In the present study, variations in pollinator activity, assemblage composition and pollen limitation were explored in the oil-producing species Nierembergia linariifolia (Solanaceae). [ABSTRACT FROM PUBLISHER]

• In animal-pollinated plants with unisexual flowers, sexual dimorphism in floral traits may be the consequence of pollinator-mediated selection. Experimental investigations of the effects of variation in flower size and floral display on pollinator visitation can provide insights into the evolution of floral dimorphism in dioecious plants. • Here, we investigated pollinator responses to experimental arrays of dioecious Sagittaria latifolia in which we manipulated floral display and flower size. We also examined whether there were changes in pollinator visitation with increasing dimorphism in flower size. • In S. latifolia, males have larger flowers and smaller floral displays than females. Visitation by pollinators, mainly flies and bees, was more frequent for male than for female inflorescences and increased with increasing flower size, regardless of sex. The number of insect visits per flower decreased with increasing floral display in males but remained constant in females. Greater sexual dimorphism in flower size increased visits to male inflorescences but had no influence on the number of visits to female inflorescences. • These results suggest that larger flower sizes would be advantageous to both females and males, and no evidence was found that females suffer from increased flower-size dimorphism. Small daily floral displays may benefit males by allowing extended flowering periods and greater opportunities for effective pollen dispersal. [ABSTRACT FROM AUTHOR]

Theory predicts that, with conflicting selection pressures mediated by mutualists and antagonists, alternative reproductive strategies can be maintained by negative frequency-dependent selection if it results in rare-morph advantage. We combined field experiments and surveys of natural populations to determine whether !election on floral display is frequency dependent in the self-incompatible herb Primula farinosa, which is polymorphic for inflorescence height and occurs in a short-scaped and a long-scaped morph. Among short-scaped plants, both pollination success, quantified as initiation of fruits and seeds, and seed predation were positively correlated with the relative frequency of the long-scaped morph. The relative strength of these effects and the direction of the resulting frequency-dependent selection on scape morph varied among years and populations. The results suggest that both mutualists and antagonists may mediate frequency-dependent selection and that frequency dependence may vary from positive to negative with rare-morph advantage, depending on the relative strength of these interactions. [ABSTRACT FROM AUTHOR]

Differences in floral traits among plant species have often been attributed to adaptation to pollinators. We explored the importance of pollinator shifts in explaining floral divergence among 15 species of Iochroma. We examined four continuously varying floral traits: corolla length, nectar reward, display size, and flower color. Pollinator associations were characterized with a continuously varying measure of pollinator importance (the product of visitation and pollen deposition) for four groups of pollinators: hummingbirds, Hymenoptera, Lepidoptera, and Diptera. A phylogenetic generalized least squares approach was used to estimate correlations between pollinator groups and floral traits across a sample of Bayesian trees using different models of trait evolution. Multivariate analyses were also employed to identify suites of traits associated with each pollinator group. We found that nonphylogenetic models typically fit the data better than phylogenetic models (Brownian motion, Ornstein–Uhlenbeck), and thus results varied little across trees. Our results indicated that species with high nectar reward and large displays are significantly more likely to be pollinated by hummingbirds and less likely to be pollinated by all groups of insects. Corolla length and flower color did not show any consistently significant associations with pollinator groups. For these two traits, we discuss alternative evolutionary forces, including phylogenetic inertia and community-level factors. [ABSTRACT FROM AUTHOR]

Plant flowering and breeding characteristics are important for us to understand the reproduction of plant populations. In this paper, we studied the reproduction characteristics of Jatropha curcas in Yuanjiang County (23°36′N, 101°00′E), Yunnan Province. The plant produces flowers in dichasial inflorescences. Normally, the flowers are unisexual, and male and female flowers are produced in the same inflorescence. Only a few male flowers are produced in an inflorescence, and fruits are produced only through pollination between different flowers from the same or different plants. By the treatments of emasculation, bagging and artificial pollination in this experiment, there were few but same fruit set ratios when the inflorescences were emasculated, bagged, or bagged with net, except artificial pollination treatments, which showed that Jatropha curcas could produce fruit through apomixis but not wind pollination. When the inflorescences were unbagged, unemasculated and with free pollination treatments, or bagged, emasculated and with artificial cross-pollination treatments, or unbagged, emasculated and with free pollination treatments, there were many fruits produced. It showed that Jatropha curcas shows outcrossing, is self-compatible, and demanding for pollinators. Normally, the male flowers open first and a few flowers bloom in one day in a raceme. These flowers last a long time in bloom. However, a large number of female flowers open from the third to the fifth day, with some female flowers opening first in a few raceme. This shows a tendency to promote xenogamy and minimize geitonogamy. [ABSTRACT FROM AUTHOR]

Variation in flower size is an important aspect of a plant’s life history, yet few studies have shown how flower size varies with environmental conditions and to what extent foliar responses to the environment are correlated with flower size. The objectives of this study were to (1) develop a theoretical framework for linking flower size and leaf size to their costs and benefits, as assessed using foliar stable carbon isotope ratio (δ13C) under varying degrees of water limitation, and then (2) examine how variation in flower size within and among species growing along a naturally occurring moisture availability gradient correlates with variation in δ13C and leaf size. Five plant species were examined at three sites in Oregon. Intra- and inter-specific patterns of flower size in relation to moisture availability were the same: the ratios of the area of flower display to total leaf area and of individual flower area to leaf area were greater at sites with more soil moisture compared to those sites with less soil moisture. The increase in flower area per unit increase in leaf area was greater at sites with more soil moisture than at sites where water deficit can occur. Values of δ13C, an index of water-use efficiency, were greater for plants with larger floral size. The patterns we observed generalize across species, irrespective of overall plant morphology or pollination system. These correlations between flower size, moisture availability, and δ13C suggest that water loss from flowers can influence leaf responses to the environment, which in turn may indirectly mediate an effect on flower size. [ABSTRACT FROM AUTHOR]

To determine whether population differentiation in flowering time is consistent with differences in current selection, we quantified phenotypic selection acting through female reproductive success on flowering phenology and floral display in two Scandinavian populations of the outcrossing, perennial herb Arabidopsis lyrata in two years. One population was located in an alpine environment strongly affected by grazing, whereas the other was close to sea level and only moderately affected by herbivory. Multiple regression models indicated directional selection for early end of flowering in one year in the lowland population, and directional selection for early start of flowering in one year in the alpine population. As expected, there was selection for more inflorescences in the lowland population. However, in the alpine population, plants with many inflorescences were selectively grazed and the number of inflorescences produced was negatively related to female fitness in one year and not significantly related to female fitness in the second year. The results are consistent with the hypothesis that genetic differentiation in flowering phenology between the study populations is adaptive, and indicate that interactions with selective grazers may strongly influence selection on floral display in A. lyrata. [ABSTRACT FROM AUTHOR]

The capacity of individual branches to store water and fix carbon can have profound effects on inflorescence size and architecture, thus on floral display, pollination, and fecundity. Mixed regression was used to investigate the relation between branch length, a proxy for plant resources, and floral display of Fouquieria splendens (ocotillo), a woody, candelabraform shrub of wide distribution in arid North America. Long branches produced three times as many flowers as short branches, regardless of overall plant size. Long branches also had more complex panicles with more cymes and cyme types than short branches; thus, branch length also influenced inflorescence architecture. Within panicles, increasing the number of cymes by one unit added about two flowers, whereas increasing the number of cyme types by one unit added about 21 flowers. Because flower production is mediated by branch length, and because most plants have branches of various lengths, the floral display of individual plants necessarily encompasses a wide range of inflorescence size and structure. [ABSTRACT FROM AUTHOR]

Population context should influence pollination success and selection on floral display in animal-pollinated plants because attraction of pollinators depends not only on the characteristics of individual plants, but also on the attractiveness of co-occurring conspecifics. The insect-pollinated herb Primula farinosa is polymorphic for inflorescence height. Natural populations may include both long-scaped plants, which present their flowers well above the soil surface, and short-scaped plants, with their flowers positioned close to the ground. We experimentally tested whether seed production in short-scaped P. farinosa varied with local morph frequency and surrounding vegetation height. In tall vegetation, short-scaped plants in polymorphic populations produced more fruit and tended to produce more seeds than short-scaped plants did in monomorphic populations. In low vegetation, population composition did not significantly affect fruit and seed output of short-scaped plants. The results suggest that long-scaped plants facilitate short-scaped plants in terms of pollinator attraction and that the facilitation effect is contingent on the height of the surrounding vegetation. The documented facilitation should contribute to the maintenance of the scape length polymorphism in ungrazed areas where litter accumulates and vegetation grows tall. [ABSTRACT FROM AUTHOR]

• Background and Aims Despite considerable investment in elaborate floral displays, Tacca chantrieri populations are predominantly selfing. It is hypothesized that this species might possess considerable spatial or temporal variation in outcrossing rates among populations. To test this hypothesis, genetic variability and genetic differentiation within and among T. chantrieri populations were investigated to find out if they are in agreement with expectations based on a predominantly inbred mating system.• Methods Genetic diversity was quantified using inter-simple sequence repeats (ISSR) in 303 individuals from 13 populations taken from known locations of T. chantrieri in China, and from one population in Thailand.• Key Results Of the 113 primers screened, 24 produced highly reproducible ISSR bands. Using these primers, 160 discernible DNA fragments were generated, of which 145 (90·62 %) were polymorphic. This indicated considerable genetic variation at the species level. However, there were relatively low levels of polymorphism at population levels, with percentages of polymorphic bands (PPB) ranging from 8·75 % to 55 %. A high level of genetic differentiation among populations was detected based on different measures (Nei''s genetic diversity analysis: GST = 0·5835; AMOVA analysis: FST = 0·6989). Furthermore, based on levels of genetic differentiation, the 14 populations clustered into two distinct groups separated by the Tanaka Line.• Conclusions High levels of differentiation among populations and low levels of diversity within populations at large spatial scales are consistent with earlier small-scale studies of mating patterns detected by allozymes which showed that T. chantrieri populations are predominantly selfing. However, it appears that T. chantrieri has a mixed-mating system in which self-fertilization predominates, but there is occasional outcrossing. Significant genetic differences between the two distinct regions might be attributed to vicariance along the Tanaka Line. Finally, possible mechanisms of geographic patterns based on genetic differentiation of T. chantrieri are discussed. [ABSTRACT FROM AUTHOR]

Almost one-third of all species in the family Orchidaceae offer no reward to insect pollinators. In the absence of a reward, floral display (number of flowers), may be the most important component of insect attraction but the role of floral display in capsule production of both deceptive (nectarless) and rewarding (nectariferous) orchids has not yet been satisfactorily explored. Based on our theoretical considerations, we propose and test here the following hypotheses: (i) deceptive species flower earlier than rewarding ones, (ii) reproductive success in deceptive species is lower than that in rewarding ones, (iii) reproductive success is independent of the number of flowers in the inflorescence in both deceptive and rewarding orchids. Our data supported hypotheses (i) and (ii). In 9 out of our 12 populations of deceptive species and in 10 out of 12 populations of rewarding species we found support for our hypothesis (iii). [ABSTRACT FROM AUTHOR]

• Background and Aims The floral display influences the composition of pollinators interacting with a plant species. Geographic and temporal variation in pollinator composition complicates the understanding of the evolutionary consequences of floral display variation. This paper analyses the relationships between Silene acutifolia, a hermaphroditic perennial herb, and its pollinators, based on field studies in the north-west of Spain.• Methods Studies were conducted over three years (1997–1999). Firstly, the main pollinators of this species were determined for two years in one population. Secondly, pollen limitation in fruit and seed production was analysed by supplementary hand pollinations, and counting the pollen grains and tubes growing in styles for two different-sized populations. Finally, the effect of flower size and number on the rate of visitation and total seed number was examined for 15 marked plants.• Results and Conclusions The primary pollinators were long-tongued insects, including Hymenoptera, Lepidoptera and Diptera, but the composition and visitation frequencies differed between years. Pollen limitation occurred in one of the years of study. There was between-population variation in the number of pollen grains and pollen tubes found in styles, suggesting pollen limitation in one population. Overall, pollinators visited plants with more open flowers more frequently, and pollinated more flowers within these plants. Conversely, petal and calyx sizes had no effect on insect visitation. Plants with higher rates of visits produced higher number of seeds, suggesting that pollinator-mediated limitation of seed and fruit production may be important in some years. [ABSTRACT FROM AUTHOR]

• Background and Aims This study examined the effect of plant traits and environmental factors on pollinator visitation in the winter-flowering Helleborus foetidus (Ranunculaceae) in three distant regions in the Iberian Peninsula.• Methods Geographical variation in floral visitor assemblage, plant traits and environmental factors were analysed during the flowering season.• Key Results Differences were found in all plant traits measured (number of open flowers, flower size, number of stamens per flower, and number of nectaries) both within and among regions, and differences among regions in all the environmental factors considered (air temperature, exposure to sunlight, canopy cover, and distance to the nearest neighbour). Differences were also found among regions in the probability that plants would be visited by pollinators.• Conclusions The results show that, although floral display (i.e. number of open flowers on a plant on a given day) consistently explained among-plant differences in visitation rate in all regions, visitation rate was not significantly affected by any other biological or environmental variable. In Helleborus foetidus, then, ‘how’ the plant is would seem to be more important than ‘where’ is it. [ABSTRACT FROM AUTHOR]

We studied the adaptive arrangement of raceme flowers in dense and sparse habitats of Salvia nipponica. We recorded bumblebee visits and collected mature seeds to estimate outcrossing rates from allozyme genotypes. To examine the resource investment in flowering stalks, we measured their length and dry mass. We found that a greater number of open flowers in a raceme enhanced bumblebee visits and successive probings in both density plots. However, greater height of a raceme did not enhance these in plots of either density. In the high-density plot, both a greater mean number of open flowers in a raceme and a greater number of flowering racemes on a plant enhanced bumblebee visits, successive probings, and also enhanced outcrossing rate in spite of an increase in successive probings. Although the number of flowers per raceme had a greater positive effect on seed-to-ovule ratios than did the number of racemes, the number of flowers per raceme may be constrained because a longer flowering stalk needs greater buckling strength. Hence, it may be advantageous for plants in high-density plots to increase both number of flowers per raceme and number of racemes. In the low-density plot, a greater number of flowering racemes on a plant enhanced pollinator visits, but a greater mean number of open flowers in a raceme did not. Hence, it may be advantageous for plants to increase the number of racemes while keeping the numbers of flowers per raceme small. Thus, the adaptive number of flowers per raceme and number of racemes per plant may differ between high- and low-density plots. [ABSTRACT FROM AUTHOR]

Mirror-image flowers (enantiostyly) have long been considered a mechanism to promote cross-pollination between flowers of alternate stylar orientation. However, in monomorphic enantiostyly, the occurrence of both left- and right-styled flowers on the same individual plant might appear to promote geitonogamy rather than outcrossing relative to the condition of dimorphic enantiostyly. We investigated daily floral display during the flowering season in two experimental populations of monomorphic enantiostylous species, Monochoria korsakowii and Monochoria vaginalis (Pontederiaceae) to assess the potential effects of floral display on geitonogamous pollination. The left- and right-styled flowers exhibited a 1:1 ratio both within individuals and populations. In M. korsakowii and M. vaginalis, 86.0% and 71.3% daily floral displays involved fewer than three flowers thus reducing the likelihood of geitonogamy. Moreover, daily displays often involved one floral form and mixed-formed with unequal ratios of left- and right-styled flowers also reducing opportunities for geitonogamy. Therefore variation in daily floral display in these two Monochoria species suggests that the impact of monomorphic enantiostyly in promoting geitonogamy will be reduced by small display sizes, or through simulating dimorphic enantiostyly. [ABSTRACT FROM AUTHOR]

Abstract: The combined occurrence of both herkogamy and dichogamy in a hermaphrodite species has been considered to strongly favour outcrossing. In this study, we investigated in detail the reproductive ecology of Gentiana straminea Maxim. (Gentianaceae), a hermaphrodite perennial endemic to the Qinghai-Tibet Plateau. In a series of observations and experiments over four consecutive years, we examined whether the combination of dichogamy and herkogamy in individual flowers completely prevents geitonogamous pollen transfer in this species. The mode of floral development clearly indicates that autonomous self-pollination is completely avoided through herkogamy and dichogamy in individual flowers. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Many flowers opened simultaneously on individual plants, the ratio of male to female phase flowers was close to 2:1 in each inflorescence at the full anthesis phase, and they were randomly distributed amongst the upper, middle and lower parts of each stem''s inflorescence. On average, Bombus sushikini Skorikov, the most frequent visitor and only legitimate pollinator of G. straminea, visited nearly two flowers per inflorescence, and four flowers per plant. Among the pollinators'' foraging bouts, the proportions of geitonogamous visits to inflorescences or flowers within an individual plant were 29% and 37%, respectively. Therefore, despite the strict dichogamous and herkogamous characteristics of the individual flowers, geitonogamous selfing might still prevail in G. straminea because of the size of its floral displays and the continuous visiting behavior of B. sushkini. [Copyright &y& Elsevier]

1. Most flowering plants display multiple flowers, so that the interaction with pollinators that determines their mating success can vary with both the characteristics of individual flowers and aggregate properties of the entire floral display, especially the number of open flowers (floral display size). These effects are seldom examined in concert and their collective consequences for interspecific differences in reproductive performance have not been considered previously.2. In this paper, we characterize the relation of pollen removal and seed production to differences in floral and inflorescence characteristics among six species of herbaceous legumes (Fabaceae).3. Several aspects of reproductive performance varied significantly among species with either plant traits or aspects of pollinator behaviour that depend on plant traits. Pollinator visitation, as measured by the ratio of pollen removal during 24 h to first-visit removal, varied positively with both nectar production per flower and floral display size. Bumble-bees visited more flowers per inflorescence on species with large floral displays, with no increase in the proportion of flowers visited. Pollen removal during a flower's first visit varied negatively among species with the mean number of flowers visited by bees per inflorescence.4. These results indicate that floral and inflorescence traits act together to influence both pollinator energetics, which affects a plant species’ attractiveness, and the rate of pollen removal, which should affect pollen export. In contrast, neither pollen removal during 24 h, nor female fecundity varied significantly with floral or display characteristics.Functional Ecology(2005)19, 245–254doi: 10.1111/j.1365-2435.2005.00961.x [ABSTRACT FROM AUTHOR]

Mating by outcrossing plants depends on the frequency and quality of the interaction between pollen vectors and individual flowers. However, the historical focus of pollination biology on individual flowers (floricentrism) cannot produce a complete understanding of the role of pollination in plant mating because mating is an aggregate process, which depends on the reproductive outcomes of all of a plant’s flowers. Simultaneous display of multiple flowers in an inflorescence increases a plant’s attractiveness to pollinators, which should, in general, enhance mating opportunities. However, whenever pollinators visit multiple flowers on an inflorescence, self-pollination among flowers can reduce the pollen available for export to other plants (pollen discounting) and can increase the incidence of inbreeding depression for embryos and offspring. Therefore, the size of floral displays that maximize mating frequency and quality generally balance the benefits of attractiveness against the costs of self-pollination. This balance can shift considerably if different flowers serve female and male functions at one time (sexual segregation) and flowers are arranged in inflorescences so that pollinators visit female flowers before male flowers. However, the effectiveness of sexual segregation depends on the extent to which a particular inflorescence architecture induces consistent movement patterns by pollinators. In general, the consistency of pollinator movement patterns varies with inflorescence architecture and differs between pollinator types. Such variation creates many options for the evolution of the diverse inflorescence characteristics observed within angiosperms, which can be appreciated only by moving beyond a floricentric perspective of the role of pollination in plant mating. [ABSTRACT FROM AUTHOR]

The terrestrial orchid Epipactis helleborine is a morphologically variable species with a wide distribution in Europe. It is pollinated by social wasps, and most populations show the morphological characteristics of outcrossing species. However, local predominantly selfing subspecies and varieties have been documented from drier habitats. To document geographic variation in floral morphology, ability to produce seeds through autogamy, and reproductive success in E. helleborine, we sampled 13 populations from three geographic regions along a latitudinal gradient of c. 1000 km from northern to southern Sweden. In the southernmost region, populations in dry and mesic habitats were compared. Supplemental hand-pollination was conducted to determine whether among-population variation in fruit set could be explained by differences in the natural level of pollination, and whether any relationship between floral morphology and fruit production could be explained by interactions with pollinators. Bagging experiments showed no evidence of autogamy in any of the study populations. Number of flowers, pollinia removal and fruit set varied significantly among populations but did not differ among regions. Pollinia removal was positively correlated with population size and both pollinia removal and fruit set were lower in dry than in mesic habitats. At the level of the individual plant, the number of pollinia removed increased more rapidly with flower number than did number of fruits produced. The hand-pollination experiment indicated that the positive relationship between number of flowers and fruit production was due to a higher degree of pollen limitation in plants with few flowers than in plants with many flowers. The experiment also showed that variation in the level of pollen limitation could only partly explain variation in fruit set among populations. [ABSTRACT FROM AUTHOR]