Plant traits, environmental factors, and pollinator visitation in winter-flowering Helleborus foetidus (Ranunculaceae)

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.     

Evolution of floral display in Eichhornia paniculata (Pontederiaceae): direct and correlated responses to selection on flower size and number

Trade-offs between flower size and number seem likely to influence the evolution of floral display and are an important assumption of several theoretical models. We assessed floral trade-offs by imposing two generations of selection on flower size and number in a greenhouse population of bee-pollinated Eichhornia paniculata. We established a control line and two replicate selection lines of 100 plants each for large flowers (S+), small flowers (S-), and many flowers per inflorescence (N+). We compared realized heritabilities and genetic correlations with estimates based on restricted-maximum-likelihood (REML) analysis of pedigrees. Responses to selection confirmed REML heritability estimates (flower size, h2 = 0.48; daily flower number, h2 = 0.10; total flower number, h2 = 0.23). Differences in nectar, pollen, and ovule production between S+ and S- lines supported an overall divergence in investment per flower. Both realized and REML estimates of the genetic correlation between daily and total flower number were r = 1.0. However, correlated responses to selection were inconsistent in their support of a trade-off. In both S- lines, correlated increases in flower number indicated a genetic correlation of r = -0.6 between flower size and number. In contrast, correlated responses in N+ and S+ lines were not significant, although flower size decreased in one N+ line. In addition, REML estimates of genetic correlations between flower size and number were positive, and did not differ from zero when variation in leaf area and age at first flowering were taken into account. These results likely reflect the combined effects of variation in genes controlling the resources available for flowering and genes with opposing effects on flower size and number. Our results suggest that the short-term evolution of floral display is not necessarily constrained by trade-offs between flower size and number, as is often assumed.     

Factors affecting pollinator movement and plant fitness in a specialized pollination system

The rate of pollen exchange within and among flowers may depend on pollinator attraction traits such as floral display size and flowering plant density. Variations in these traits may influence pollinator movements, pollen receipt, and seed number. To assess how floral display size and flowering plant density affect parameters of pollinator visitation rate, pollen receipt per flower, seed number per fruit and the between-plant pollinator movements, we studied the self-incompatible plant, Nierembergia linariifolia. Per-flower pollinator visitation rate and bout length increased linearly with increasing floral display size. Pollen receipt per flower increased linearly with increasing flowering plant density. For seed number per fruit, a polynomial model describing an increased seed number per fruit at low density and a decreased seed number per fruit at high density provided a significant fit. Per-flower pollinator visitation rate was not associated with pollen receipt per flower and seed number per fruit. Bees visited plants located near to the center of the population more frequently than plants located at the periphery. Increases in both floral display size and flowering plant density led to an increased chance of a plant being chosen as the center of the pollinator foraging area. These results suggest that even though large floral displays and high flowering plant density are traits that attract more pollinators, they may also reduce potential mate diversity by restricting pollen movement to conspecific mates that are closely located.     

Evolution of floral display in Eichhornia paniculata (Pontederiaceae): genetic correlations between flower size and number

The evolution of floral display is thought to be constrained by trade‐offs between the size and number of flowers and inflorescences. We grew in the glasshouse 60 maternal families from each of two Brazilian populations of the annual herb, Eichhornia paniculata. We measured flower size, daily flower number, and total flower number per inflorescence, and two indices of module size, leaf area and age at flowering. We also assessed the size and number of inflorescences produced over 6 weeks. All floral traits exhibited significant heritable variation, some of which was due to genetic variation in module size. Genetic (maternal family) correlations between daily and total flower number did not differ from 1.0, indicating that display size (daily flower number) cannot evolve independently from total flower number per inflorescence. Genetic correlations between flower size and daily flower number ranged from negative to positive (r=–0.78 to +0.84), depending on population and inflorescence. Positive correlations occurred when variation in investment per inflorescence was high so that some families produced both larger and more flowers. These correlations became zero when we controlled for variation in module size. Families that flowered later produced fewer, larger inflorescences (r=–0.33, –0.85). These data support theoretical predictions regarding the combined effects of variation in resource acquisition and allocation on traits involved in trade‐offs, and they emphasize the hierarchical organization of floral displays. Our results imply that patterns of resource allocation among inflorescences influence evolutionary changes in flower size and number per inflorescence.     

Pollinator responses to variation in floral display and flower size in dioecious Sagittaria latifolia (Alismataceae)

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.     

A test of the effect of floral color change on pollination effectiveness using artificial inflorescences visited by bumblebees

Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2–4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.     

The effect of flower position on variation and covariation in floral traits in a wild hermaphrodite plant

Background  

Floral traits within plants can vary with flower position or flowering time. Within an inflorescence, sexual allocation of early produced basal flowers is often female-biased while later produced distal flowers are male-biased. Such temporal adjustment of floral resource has been considered one of the potential advantages of modularity (regarding a flower as a module) in hermaphrodites. However, flowers are under constraints of independent evolution of a given trait. To understand flower diversification within inflorescences, here we examine variation and covariation in floral traits within racemes at the individual and the maternal family level respectively in an alpine herb Aconitum gymnandrum (Ranunculaceae).     

Genetic variation in the reduction of attractive floral traits of an annual tarweed in response to drought and apical damage

Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators. Plant genotypes may differ in their responses to the interplay between these factors, and evolution of phenotypic plasticity could be expected, particularly in heterogeneous environments. We aimed at evaluating the effects of simulated herbivory and experimental drought on floral traits attractive to pollinators in genetic families of the annual tarweed Madia sativa, which inhabits heterogeneous environments in terms of water availability, herbivore abundance and pollinator abundance.Methods In a greenhouse experiment with 15 inbred lines from a M. sativa population located in central Chile (Mediterranean-type climate), we measured the effects of apical bud damage and reduced water availability on: number of ray florets per flower head, length of ray florets, flower head diameter, number of open flower heads per plant, flowering plant height and flowering time.Important findings Apical damage and water shortage reduced phenotypic expression of floral traits attractive to pollinators via additive and non-additive effects. Plants in low water showed decreased height and had fewer and shorter ray florets, and fewer and smaller flower heads. Damaged plants showed delayed flowering, were less tall, and showed shorter ray florets and smaller flower heads. The number of ray florets was reduced by damage only in the low water treatment. Plant height, flowering time and number of flower heads showed among-family variation. These traits also showed genetic variation for plasticity to water availability. Ray floret length, flower head size and time to flowering showed genetic variation for plastic responses to apical damage. Plasticity in flowering time may allow M. sativa to adjust to the increased aridity foreseen for its habitat. Because genetic variation for plastic responses was detected, conditions are given for evolutionary responses to selective forces acting on plastic traits. We suggest that the evolution of adaptive floral plasticity in M. sativa in this ecological scenario (heterogeneous environments) would result from selective forces that include not only pollinators but also resource availability and herbivore damage.     

Refuse attracts? Effect of refuse dumps of leaf‐cutting ants on floral traits

The nutrient‐rich organic waste generated by ants may affect plant reproductive success directly by enhancing fruit production but also indirectly, by affecting floral traits related with pollinator attraction. Understanding how these soil‐nutrient hot spots influence floral phenotype is relevant to plant–pollination interactions. We experimentally evaluated whether the addition of organic waste from refuse dumps of the leaf‐cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae: Attini) alters floral traits associated with pollinator attraction in Eschscholzia californica (Ranunculales: Papaveraceae), an entomophilous herb. We analysed flower shape and size using geometric morphometric techniques in plants with and without the addition of refuse‐dumps soil, under greenhouse conditions. We also measured the duration of flowering season, days with new flowers, flower production and floral display size. Plants growing in refuse‐dumps soil showed higher flower shape diversity than those in control soil. Moreover, plants in refuse‐dumps soil showed bigger flower and floral display size, longer flowering season, higher number of flowering days and flower production. As all these variables may potentially increase pollinator visits, plants in refuse‐dumps soil might increase their fitness through enhanced attraction. Our work describes how organic waste from ant nests may enhance floral traits involved in floral attraction, illustrating a novel way of how ants may indirectly benefit plants.     

Variation of nectar production in relation to plant characteristics in protandrous Aconitum gymnandrum

Aims Floral nectar plays a vital role in plant reproductive success by attracting pollinators. Nectar traits of a flower can depend directly on plant characteristics other than environmental factors and exhibit extensive flower- and plant-level variations. Studies on nectar traits frequently focused on intraplant variation for dichogamous plants, but few have paid attention to both intra- and interplant nectar variations in relation to plant characteristics. Revealing within- and among-plant variation and its relative magnitude is important for our understanding of how pollinator-mediated selection can act on nectar traits and evolution of nectar traits.Methods Through investigating protandrous Aconitum gymnandrum populations at the Alpine Meadows and Wetland Ecosystems Research Station of Lanzhou University, we examined the relationships between nectar production per flower and plant characteristics (e.g. flower position within inflorescences, floral sexual phases, flowering time, inflorescence size and floral attractive traits).Important findings A. gymnandrum exhibited a declining gradient in the nectar volume along inflorescences, with more nectar in basal flowers than distal ones. Protandrous flowers of A. gymnandrum did not show gender-biased nectar production while the nectar volume varied with different stages of floral sexual phases. The significant correlation between the first flowering date of individuals and the mean nectar volume per flower was positive in 2013, but became negative in 2014, suggesting complex effects of biotic and abiotic factors. The mean nectar volume per flower was not related to inflorescence size (the number of total flowers per plant). Furthermore, nectar production was weakly associated with floral attractive traits (the petal width and the galea height), even if the effect of flowering time of individuals was removed, suggesting that the honesty of floral traits as signals of nectar reward for pollinators is not stable in this species.     

水蓼花大小在花序和个体上的变化及其与数量权衡关系研究

探讨一年生植物水蓼花大小在花序上和个体上的变化及花大小与花数量的权衡关系。在54株植物个体上随机选取一花序,在花序的基部、中部和顶部各选取1～2朵花,花大小(生物量)以基部最大(0.851mg),顶部最小(0.715mg),可能是由结构效应引起的。在每个体上随机采集4～20朵花,以其均值表示植物个体的花大小,花大小不随植物个体大小变化而变化。花朵展示和总花数均随个体增大而增加。在控制植物个体大小(地上部分营养器官生物量)后,没有发现花朵展示或花数量与花大小之间的权衡关系,表明个体资源水平的差异可能掩盖了花数量与大小间的权衡关系。     

Reproductive success in varying light environments: direct and indirect effects of light on plants and pollinators

Plant populations often exist in spatially heterogeneous environments. Light level can directly affect plant reproductive success through resource availability or by altering pollinator behavior. It can also indirectly influence reproductive success by determining floral display size which may in turn influence pollinator attraction. We evaluated direct and indirect effects of light availability and measured phenotypic selection on phenological traits that may enhance pollen receipt in the insect-pollinated herb Campanulastrum americanum. In a natural population, plants in the sun had larger displays and received 7 times more visits than plants in the shade. Using experimental arrays to separate the direct effects of irradiance on insects from their response to display size, we found more visits to plants in the sun than in the shade, but no association between number of visits each flower received and display size. Plants in the sun were not pollen limited but pollen-augmented shade flowers produced 50% more seeds than open-pollinated flowers. Phenological traits, which may influence pollen receipt, were not under direct selection in the sun. However, earlier initiation and a longer duration of flowering were favored in the shade, which may enhance visitation in this pollen-limited habitat.     

Environmental contribution to floral trait variation in Chamaecrista fasciculata (Fabaceae: Caesalpinoideae)

Although intraspecific variation in plant floral traits has been documented for a number of plant species, the causes of such variation are largely unknown. We first quantified floral trait variation in an Illinois prairie population of Chamaecrista fasciculata Michx. We then used a field experiment to determine the contribution of leaf herbivory to this variation and a greenhouse experiment to determine the contribution of leaf herbivory, and variable soil nutrient and water content to floral trait variation. Variation in environmental factors explained a significant portion of the naturally occurring variation in corolla width, ovule number, ovule size, and anther length. In the field, manual removal of 25% or more leaf area reduced ovule size and anther length (and by inference, pollen production), and delayed flowering. In the greenhouse, plants from which we removed 25% or more of their leaf area or which were given limited water produced fewer ovules than control plants. Addition of nutrients interacted with soil moisture to affect corolla diameter and ovule number. Despite our demonstration of significant environmental impacts on reproductive traits, these impacts were relatively much smaller than those on plant size, suggesting that floral traits are buffered against variable resource availability.     

How do visitation patterns vary among pollinators in relation to floral display and floral design in a generalist pollination system?

Diverse pollinator assemblages may impose complex selection and thus limit specialisation to particular pollinators. Previous work has concentrated on how visitation rates of different pollinators vary in space and time and how pollinators may vary in efficiency. In this study I quantify variation in visitation rates and foraging behaviour of different insect types (1) in space and time and (2) in relation to variation in floral design (flower size and form) and floral display (number of open flowers) for the distylous clonal shrub Jasminum fruticans. Mean visitation rate showed a significant interaction between insect type and population for seven populations in one year, and between insect types and years for a single population over 3 years. There was also a significant interaction between insect type and population for the proportion of flowers visited. In general the number of visits was positively related to the number of open flowers in a patch, but analyses by insect type showed that this was only true for bee flies and butterflies. Short-tongued bees showed a positive relationship between visitation rate and the number of open flowers on the focal stem, and hawkmoths and butterflies made more visits to plants with larger flowers. Hawkmoths were the only insect type to show a positive relation between the number of flowers visited per foraging bout and flower size. The significant differences between different insect types in patterns of variation in visitation rates in response to floral design and display may act to diversify selection on floral traits, and thereby constrain specialisation of the plant to particular pollinators.     

Modification of bumblebee behavior by floral color change and implications for pollen transfer in <Emphasis Type="Italic">Weigela middendorffiana</Emphasis>

Flowers of Weigela middendorffiana change the color from yellow to red. The previous study revealed that red-phase flowers no longer have sexual function and nectar, and bumblebees selectively visit yellow-phase flowers. The present study examined how retaining color-changed flowers can regulate the foraging behavior of bumblebees and pollen transport among flowers within (geitonogamous pollination) and between (outcrossing pollination) plants and how the behavior is influenced by display size (i.e., number of functional flowers) and visitation frequency. The visitation frequencies of bumblebees to plants and successive flower probes within plants were observed in the field using plants whose flower number and composition of the two color-phase flowers had been manipulated. To evaluate pollination efficiency over multiple pollinator visits, a pollen transport model was constructed based on the observed bumblebee behavior. In the simulation, three flowering patterns associated with display size and existence of color-changed flowers were postulated as follows: Type 1, large display (100 functional flowers) and no retention of color-changed flowers; Type 2, small display (50 functional flowers) and retention of color-changed flowers (50 old flowers), and; Type 3, large display (100 functional flowers) and retention of color-changed flowers (100 old flowers). Color-changed flowers did not contribute to increasing bumblebee attraction at a distance but reduced the number of successive flower probes within plants. Comparisons of pollen transfer between Types 1 and 3 revealed that the retention of color-changed flowers did not influence the total amount of pollen exported when pollinator visits were abundant (>100 visits) but decreased geitonogamous pollination. Comparisons between Types 2 and 3 revealed that the discouragement effect of floral color change on successive probes accelerated in plants with a large display size. Overall, the floral color change strategy contributed to reduce geitonogamous pollination, but its effectiveness was highly sensitive to display size and pollinator frequency.     

Differential self‐fertilization rates in response to variation in floral traits within inflorescences of Aquilegia buergeriana var. oxysepala (Ranunculaceae)

To assess variation in the proportion of self‐fertilized seeds among flowers within inflorescences and the relationship between floral traits and the rate of self‐fertilization, the proportion of self‐fertilized seeds among individual flowers was estimated using ten microsatellite markers in self‐compatible plants of Aquilegia buergeriana var. oxysepala. Within‐inflorescence variation in floral traits, such as the duration of the male and female phases, flower size, herkogamy and the number of pollen grains and ovules in two natural populations, were investigated. The first flower in an inflorescence produced more seeds and a higher proportion of self‐fertilized seeds than the second flower. The higher proportion of self‐fertilized seeds in the first flowers was accompanied by a higher number of pollen grains and ovules in the bud stage and the female phase. These results indicate that the high proportion of self‐fertilized seeds in the first flowers in an inflorescence may be due to the high number of remaining pollen grains in the female phase. This suggests that variation in floral traits within inflorescences affects seed quality and quantity among flowers within inflorescences.     

Relative impact of mate versus pollinator availability on pollen limitation and outcrossing rates in a mass‐flowering species

Plant mating systems are driven by several pre‐pollination factors, including pollinator availability, mate availability and reproductive traits. We investigated the relative contributions of these factors to pollination and to realized outcrossing rates in the patchily distributed mass‐flowering shrub Rhododendron ferrugineum. We jointly monitored pollen limitation (comparing seed set from intact and pollen‐supplemented flowers), reproductive traits (herkogamy, flower size and autofertility) and mating patterns (progeny array analysis) in 28 natural patches varying in the level of pollinator availability (flower visitation rates) and of mate availability (patch floral display estimated as the total number of inflorescences per patch). Our results showed that patch floral display was the strongest determinant of pollination and of the realized outcrossing rates in this mass‐flowering species. We found an increase in pollen limitation and in outcrossing rates with increasing patch floral display. Reproductive traits were not significantly related to patch floral display, while autofertility was negatively correlated to outcrossing rates. These findings suggest that mate limitation, arising from high flower visitation rates in small plant patches, resulted in low pollen limitation and high selfing rates, while pollinator limitation, arising from low flower visitation rates in large plant patches, resulted in higher pollen limitation and outcrossing rates. Pollinator‐mediated selfing and geitonogamy likely alleviates pollen limitation in the case of reduced mate availability, while reduced pollinator availability (intraspecific competition for pollinator services) may result in the maintenance of high outcrossing rates despite reduced seed production.     

新疆郁金香一居群个体性别7年的动态变化

在雌雄同株植物中, 花性别被认为是两性资源分配对环境条件的响应, 了解个体性别随时间的变化对探讨植物性系统的变异有重要意义。早春短命植物新疆郁金香(Tulipa sinkiangensis)多为两性花居群, 前期调查显示一些居群由雄花和两性花构成。为了探讨新疆郁金香雄花的发生与变化, 我们连续7年对一个居群的花性别及其变化动态进行了跟踪。结果显示: (1)该居群主要是由一朵花植株和两朵花植株构成, 分别占居群植株总数的74.5%和23.0%。两种性别的花随机分布在不同类型的单株上, 形成了以两性花植株为主, 含有雄株、雄花与两性花同株(andromonoecy)的居群结构。(2)雄花相对较小, 子房退化, 无胚珠发育, 在植株或居群中花期较晚出现。与相同大小的两性花相比, 雄花在单花花粉量、花粉败育率、花粉粒大小及形态、雄性功能等方面没有差异。(3) 7年间, 雄花在居群中的比例经历了2011-2014年间的显著下降(23.4-3.1%)和2015-2017年间相对稳定的零星分布(1.5-1.0%)两个阶段。居群中一朵花植株数量和两朵花植株数量在年份间呈波动性变化。(4)雄花的出现可能是植株受自身资源状况及环境条件等因素的影响在花性别选择上作出的可塑性反应。     

Reproductive patterns within racemes in protandrous Aconitum gymnandrum (Ranunculaceae): potential mechanism and among-family variation

The adaptive significance and mechanism of patterns in floral sex allocation and female success within inflorescences has attracted attention recently, whereas few studies have examined genetic variation of intra-inflorescence pattern. The purpose of this study is to investigate patterns of reproduction within racemes in protandrous Aconitum gymnandrum Maxim., and illuminate potential mechanisms and genetic variation of such patterns. Data from pot experiment on 40 maternal families were collected in field. Anther number, pollen:ovule ratio and seed germination rate increased from bottom to top flowers within racemes, but other traits, such as gynoecium mass, carpel number, sepal galea height and seed production decreased significantly with flowering sequence. Variation in floral sex allocation within racemes in A. gymnandrum fitted entirely the prediction of protandry, which was not a result of architectural effect. Such selected pattern may result from a variety of factors influencing the mating environment, such as pollinator directionality, display size and flower longevity. Decline of female success within racemes in A. gymnandrum also resulted from male-biased allocation selected by variation in the mating environment, not resource competition or pollen limitation. Moreover, there was genetic variation for most reproductive traits and the position effect, as evinced by significant variation among families.     

毛茛状金莲花不同花期的花特征和访花昆虫的变化及表型选择

为了研究植物生长季内开花时间对花特征表型选择的影响,我们以青藏高原东缘高寒草地的毛茛状金莲花Trollius ranunculoides)为实验材料,在生长季内不同开花时间(花前期、花末期)测定花特征,观察访花昆虫的类群和访花频率,生长季结束后收集种子.根据昆虫访花的喜好和季节内类群与访花频率的变化,分析了不同开花时间毛茛状金莲花的花特征与昆虫的选择;并用种子产量表示雌性适合度,估计了毛茛状金莲花的花特征在不同开花时间所受的表型选择.结果表明:不同花期植物的花特征有显著差异,相应的访花昆虫的类群和频率也存在差异,不同类群昆虫访花喜好也不一样.蜂喜好花瓣和花萼较宽、花茎短和花茎数少的个体,这正符合花前期的特征,因而蜂的访花频率在花前期较高;蝇对花特征没有明显的偏好.而通过雌性适合度估计毛茛状金莲花花特征所受的表型选择则是:花前期,花茎较长和花茎数多的植株适合度大;花末期,花茎数多的植株适合度大.我们的研究表明:在植物生长季,花期的分化伴随着传粉昆虫活动的变化.不同花期,访花昆虫的变化可能对植物花特征的分化起了至关重要的作用.但是访花昆虫对花特征的选择与通过雌性适合度估计植物受到的选择不尽相同,这可能是由于其他因素造成的.