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The effect of floral traits, floral rewards and plant water availability on plant–pollinator interactions are well-documented; however, empirical evidence of their impact on flowering phenology in high-elevation meadows remains scarce. In this study, we assessed three levels of flowering phenology, i.e. population-, individual- and flower-level (floral longevity), in two nearby but contrasting (wet versus dry) sub-alpine meadows on Yulong Snow Mountain, southwestern China. We also measured a series of floral traits (pollen number, ovule number, and the ratio of pollen to ovule number per flower, i.e. pollen:ovule ratio [P/O]) and floral rewards (nectar availability and pollen presentation) as plausible additional sources of variation for each phenological level. Floral longevity in the wet meadow was significantly longer than that for the dry meadow, whereas population- and individual-flowering duration were significantly shorter. Our results showed a significant positive relationship between flowering phenology with pollen number and P/O per flower; there was no relationship with ovule number per flower. Further, we found a significant effect of flowering phenology on nectar availability and pollen presentation. Our findings suggest that shorter floral longevity in dry habitats compared to wet might be due to water-dependent maintenance costs of flowers, where the population- and individual-level flowering phenology may be less affected by habitats. Our study shows how different levels of flowering phenology underscore the plausible effects of contrasting habitats on reproductive success. [ABSTRACT FROM AUTHOR]

Most orchids have high ornamental value with long-lived flowers. However, the mechanisms by which orchids maintain floral longevity are poorly understood. Here, we hypothesized that floral longevity in Dendrobium is maintained by high resource investment and complementary water and nutrient utilization in different structural units of the perianth. To test this hypothesis, we determined which water- and nutrient-related traits are correlated with flower longevity in 23 Dendrobium species or cultivars, and examined variations of the related traits during flower development of one long-lived cultivar. We found that floral longevity was correlated with dry mass per unit area of perianths and total flower biomass, which indicates that maintaining floral longevity requires increased resource investment. During development of long-lived flowers, labella showed a high capacity for water storage and nutrient reutilization, which could partly remedy high water demand and biomass investment. Sepals and petals, in contrast, had stronger desiccation avoidance and higher metabolic activity with lower biomass investment. These findings indicate that Dendrobium flowers maintain longevity by complementary water and nutrient utilization strategies in the sepals, petals and labella, with labella consuming more water and nutrients to extend flower display, and sepals and petals using a more conservative strategy. [ABSTRACT FROM AUTHOR]

Sexual interference between male and female function in hermaphrodite plants is reduced by protandry. In environments with insufficient pollinator service, prolongation of male function owing to limited pollen removal could restrict the duration of female function and lower seed production. We provide evidence that this form of sexual conflict has played a role in the spread of females in gynodioecious populations of Cyananthus delavayi in the pollen‐limited environments in which this subalpine species occurs. Using field experiments involving artificial pollen removal from the strongly protandrous flowers of hermaphrodites, we demonstrated a trade‐off between male‐ and female‐phase duration with no influence on overall floral longevity. Pollen removal at the beginning of anthesis resulted in hermaphrodite seed production matching that of females. In contrast, restricted pollen removal increased the duration of male function at the expense of female function lowering maternal fertility compared to females. This pattern was evident in five populations with females experiencing a twofold average seed fertility advantage compared to hermaphrodites. Gynodioecy often appears to evolve from protandrous ancestors and pollen limitation is widespread in flowering plants suggesting that sexual conflict may play an unappreciated role in the evolution of this form of sexual dimorphism. [ABSTRACT FROM AUTHOR]

Background and Aims Plasticity of floral traits in response to pollination can enable plants to maximize opportunities for pollen import and export under poor pollination conditions, while minimizing costs under favourable ones. Both floral longevity and display are key traits influencing pollination. While pollination-induced flower wilting is widely documented, we lack an understanding of the multifactorial complexity of this response, including the influence of other pollination components, costs of extended longevity and subsequent impacts on floral display. Methods Plasticity of floral longevity was experimentally evaluated in Sabatia angularis in response to multiple pollination factors: pollen addition, removal, and source (self, single-donor outcross, multiple-donor outcross) and timing of pollination. Effects of pollen quantity were further evaluated by exploiting variation in autonomous self-pollen deposition. Delayed pollination costs were tested comparing seed set from early versus late pollinations. Finally, I compared floral display metrics (peak floral display, time to peak flower, flowering duration, mean flowering rate) between experimentally pollinated and control plants. Key Results Floral longevity was highly plastic in response to pollen addition and its timing, and the response was dose-dependent but insensitive to pollen source. Pollen removal tended to extend floral longevity, but only insofar as it precluded pollination-induced wilting via autonomous self-pollination. Under delayed pollination, the wilting response was faster and no cost was detected. Pollination further led to reduced peak floral displays and condensed flowering periods. Conclusions Floral longevity and display plasticity could optimize fitness in S. angularis, a species prone to pollen limitation and high inbreeding depression. Under pollinator scarcity, extended floral longevities offer greater opportunities for pollen receipt and export at no cost to seed set, reproductive assurance via autonomous self-pollination and larger, more attractive floral displays. Under high pollinator availability, shortened longevities lead to smaller displays that should lower the risk of geitonogamy. [ABSTRACT FROM AUTHOR]

* Background and Aims Evolution of autonomous selfing may be advantageous because it allows for reproductive assurance. In co-flowering plants competing for pollinators, the least common and/or attractive could suffer pollen limitations. Silene niceensis and S. ramosissima are taxonomically related species sharing the same habitat, although S. ramosissima is less abundant and has a more restricted distribution. They also have the same a priori nocturnal pollinator syndrome, and show an overlapping flowering phenology. The aim of this study was to investigate whether a selfing strategy in S. ramosissima allows it to avoid pollinator competition and/or interspecific pollen transfer with S. niceensis, which would thus enable both species to reach high levels of fruit and seed set. * Methods The breeding system, petal colour, flower life span and degree of overlap between male and female phases, floral visitor abundance and visitation rates were analysed in two sympatric populations of S. niceensis and S. ramosissima in southern Spain. * Key Results Autonomous selfing in S. ramosissima produced very high fruit and seed set, which was also similar to open-pollinated plants. Silene niceensis showed minimum levels of autonomous selfing, and pollen/ovule ratios were within the range expected for the breeding system. In contrast to S. niceensis, flower life span was much shorter in S. ramosissima, and male and female organs completely overlapped in space and time. Upper surface petals of both species showed differing brightness, chroma and hue. Flowers of S. niceensis were actively visited by moths, hawkmoths and syrphids, whereas those of S. ramosissima were almost never visited. * Conclusions The findings show that different breeding strategies exist between the sympatric co-flowering S. niceensis and S. ramosissima, the former specializing in crepuscular-nocturnal pollination and the latter mainly based on autonomous selfing. These two strategies allow both species to share the restricted dune habitat in which they exist, with a high female reproductive success due to the absence of pollinator competition and/or interspecific pollen flow. [ABSTRACT FROM AUTHOR]

Aims Floral longevity, the duration that a flower remains open and functional, varies greatly among species. Variation in floral longevity has been considered to be optimal strategy for resource allocation under different ecological conditions, mainly determined by the rates of pollination and cost of flower maintenance. However, it is unclear whether an intrinsic factor, floral sexual investment, constrains evolution of floral longevity. The theoretical model also predicts that dichogamy favors long-lived flowers, but empirical studies to test this prediction remain unexplored. Methods To examine the effect of floral sexual investment on floral longevity, we measured flower size together with pollen and ovule production in 37 sympatric flowering plants in a natural community. The duration of the female and male phase in 21 protandrous species and floral longevity of the other 16 adichogamous species were documented in the field. Important Findings Floral longevity varied from 1 day to 15 days, while pollen number per flower varied from 643 to 710 880 and ovule number per flower from 1 to 426 in the 37 species. Flower size was correlated with pollen production as well as ovule production. Floral longevity was positively related to pollen production but not to ovule production. Consistent with the prediction that dichogamy favors long-lived flowers, we found the floral longevity of protandrous species was significantly longer than that of adichogamous species. In the protandrous species, pollen production per flower was observed to be positively related to male duration, while ovule production was not related to female duration. Our analyses of variation in floral longevity and sexual investment among different species suggest that the floral sexual investment could be an intrinsic factor contributing to the selected floral longevity, particularly the male phase, and that high pollen production could potentially increase pollen removal, i.e. male productive success. [ABSTRACT FROM AUTHOR]

Background and Aims A plant investing in reproduction partitions resources between flowering and seed production. Under resource limitation, altered allocations may result in floral trait variations, leading to compromised fecundity. Floral longevity and timing of selfing are often the traits most likely to be affected. The duration of corolla retention determines whether fecundity results from outcrossing or by delayed selfing-mediated reproductive assurance. In this study, the role of pollination schedules and soil water availability on floral longevity and seed production is tested in Collinsia heterophylla (Plantaginaceae). Methods Using three different watering regimes and pollination schedules, effects on floral longevity and seed production were studied in this protandrous, flowering annual. Key Results The results reveal that soil water status and pollination together influence floral longevity with low soil water and hand-pollinations early in the floral lifespan reducing longevity. However, early pollinations under excess water did not extend longevity, implying that resource surplus does not lengthen the outcrossing period. The results also indicate that pollen receipt, a reliable cue for fecundity, accelerates flower drop. Early corolla abscission under drought stress could potentially exacerbate sexual conflict in this protandrous, hermaphroditic species by ensuring self-pollen paternity and enabling male control of floral longevity. While pollination schedules did not affect fecundity, water stress reduced per-capita seed numbers. Unmanipulated flowers underwent delayed autonomous selfing, producing very few seeds, suggesting that inbreeding depression may limit benefits of selfing. Conclusions In plants where herkogamy and dichogamy facilitate outcrossing, floral longevity determines reproductive success and mating system. Reduction in longevity under drought suggests a strong environmental effect that could potentially alter the preferred breeding mode in this mixed-mated species. Extrapolating the findings to unpredictable global drought cycles, it is suggested that in addition to reducing yield, water stress may influence the evolutionary trajectory of plant mating system. [ABSTRACT FROM AUTHOR]

Background and aims Pollination-induced floral changes, which have been widely documented in flowering plants, have been assumed to enhance the plant's reproductive success. However, our understanding of the causes and consequences of these changes is still limited. Using an alpine gynodioecious species, Cyananthus delavayi, we investigated the factors affecting floral closure and estimated the fitness consequences of floral closure. Methods The timings of floral closure and fertilization were determined. The effects of pollen load, pollen type (cross- or self-pollen) and floral morph (female or perfect flower) on the occurrence of floral closure were examined. Ovule fertilization and seed production were examined to investigate the causes and consequences of floral closure. Flowers were manipulated to prevent closing to detect potential benefits for female fitness. Key Results Floral closure, which could be induced by a very low pollen load, occurred within 4–7 h after pollination, immediately following fertilization. The proportion of closed flowers was influenced by pollen load and floral morph, but not by pollen type. Floral closure was more likely to occur in flowers with a higher proportion of fertilized ovules, but there was no significant difference in seed production between closed and open flowers. Those flowers in which closure was induced by natural pollination had low fruit set and seed production. Additionally, seed production was not influenced by closing-prevented manipulation when sufficient pollen deposition was received. Conclusions The occurrence of floral closure may be determined by the proportion of fertilized ovules, but this response can be too sensitive to ensure sufficient pollen deposition and can, to some extent, lead to a cost in female fitness. These results implied that the control of floral receptivity by the recipient flowers does not lead to an optimal fitness gain in C. delavayi. [ABSTRACT FROM AUTHOR]

In flowering plants, the onset and duration of female receptivity vary among species. In several species the receptive structures wilt upon pollination. Here we explore the hypothesis that postpollination wilting may be influenced by pollen and serve as a general means to secure paternity of the pollen donor at the expense of female fitness. Taking a game-theoretical approach, we examine the potential for the evolution of a pollen-borne wilting substance, and for the coevolution of a defense strategy by the recipient plant. The model without defense predicts an evolutionarily stable strategy (ESS) for the production of wilting substance. The ESS value is highest when pollinator visiting rates are intermediate and when the probability that pollen from several donors arrives at the same time is low. This finding has general implications in that it shows that male traits to secure paternity also can evolve in species, such as plants, where mating is not strictly sequential. We further model coevolution of the wilting substance with the timing of stigma receptivity. We assume that pollen-receiving plants can reduce the costs induced by toxic pollen by delaying the onset of stigmatic receptivity. The model predicts a joint ESS, but no female counter-adaptation when the wilting substance is highly toxic. This indicates that toxicity affects the probability that a male manipulative trait stays beneficial (i.e., not countered by female defense) over evolutionary time. We discuss parallels to male induced changes in female receptivity known to occur in animals and the role of harm for the evolution of male manipulative adaptations. [ABSTRACT FROM AUTHOR]