Horizontal orientation of zygomorphic flowers: significance for rain protection and pollen transfer

• Floral traits are recognized to have evolved under selection for abiotic and biotic factors. Complex zygomorphic flowers usually face horizontally. It has been proved that a horizontal orientation facilitates pollinator recognition and pollination efficiency, but its significance in adaptation to abiotic factors remains unknown.
• The floral orientation of Abelia × grandiflora naturally varies around horizontal (with an angle of ?30 to +33° between the floral main axis and the horizontal). We examined whether three different floral orientations affected flower thermal conditions, response to rain and pollination.
• Results showed that floral orientation had no effect on diurnal variations in flower temperature. The anthers of all three flower orientations were wetted by rainfall, but the inclined upward‐facing flowers contained significantly more rainwater. The horizontal flowers received significantly higher visitation by hawkmoths and had a higher stigmatic pollen load. In contrast, the upward flower orientation reduced pollination precision, while downward‐facing flowers had decreased pollinator attraction.
• This study indicates that horizontal flowers may have evolved as a trade‐off between rain protection and pollination. Zygomorphic flowers that deviate from a horizontal orientation may have lower fitness because of flower flooding by rainwater and decreased pollen transfer.

     

Change of floral orientation affects pollinator diversity and their relative importance in an alpine plant with generalized pollination system,Geranium refractum (Geraniaceae)

Floral orientation may affect pollinator attraction and pollination effectiveness, and its influences may differ among pollinator species. We, therefore, hypothesized that, for plant species with a generalized pollination system, changes in floral orientation would affect the composition of pollinators and their relative contribution to pollination. Geranium refractum, an alpine plant with downward floral orientation was used in this study. We created upward-facing flowers by altering the flower angle. We compared the pollinator diversity, pollination effectiveness, and pollinator importance, as well as female reproductive success between flowers with downward- and upward-facing orientation. Results indicated that the upward-facing flowers were visited by a wider spectrum of pollinators (classified into functional groups), with higher pollinator diversity than natural flowers. Moreover, due to influences on visitation number and pollen removal, the pollinator importance exhibited by the main pollinator groups differed between flower types. Compared with natural flowers, the pollination contribution of principal pollinators (i.e., bumblebees) decreased in upward-facing flowers and other infrequent pollinators, such as solitary bees and muscoid flies, removed more pollen. Consequently, stigmatic pollen loads were lower in upward- than in downward-facing flowers. These findings reveal that floral orientation may affect the level of generalization of a pollination system and the relative importance of diverse pollinators. In this species, the natural downward-facing floral orientation may increase pollen transfer by effective pollinators and reduce interference by inferior pollinators.     

The missing stink: sulphur compounds can mediate a shift between fly and wasp pollination systems

The radiation of the angiosperms is often attributed to repeated evolutionary shifts between different pollinators, as this process drives diversification of floral forms and can lead to reproductive isolation. Floral scent is an important functional trait in many pollination systems but has seldom been implicated as a key mechanism in pollinator transitions. In this study, we suggest a role for sulphur compounds in mediating a shift between specialized carrion-fly and pompilid-wasp pollination systems in Eucomis (Hyacinthaceae). Flowers of closely related Eucomis species pollinated by carrion flies or pompilid wasps have very similar greenish-white flowers, but differ markedly in floral scent chemistry (determined by GC–MS analysis of headspace extracts). Comparison of the floral colours of the four Eucomis species in the visual systems of flies and wasps suggests that colour plays little role in pollinator discrimination. Nectar properties and morphology also do not differ strongly between fly- and wasp-pollinated flowers. By comparing floral scent bouquets and experimentally manipulating the scent of plants in the field, we demonstrate that shifts between wasp and fly pollination in these four congeners can depend on the production or suppression of sulphur compounds (dimethyl disulphide and dimethyl trisulphide) in the fragrance bouquet. This suggests that mutations affecting the production of particular scent compounds could precipitate shifts between pollinators, independently of floral morphology, colour or nectar properties.     

Phenotypic selection on flowering phenology and pollination efficiency traits between Primula populations with different pollinator assemblages

Floral traits have largely been attributed to phenotypic selection in plant–pollinator interactions. However, the strength of this link has rarely been ascertained with real pollinators. We conducted pollinator observations and estimated selection through female fitness on flowering phenology and floral traits between two Primula secundiflora populations. We quantified pollinator‐mediated selection by subtracting estimates of selection gradients of plants receiving supplemental hand pollination from those of plants receiving open pollination. There was net directional selection for an earlier flowering start date at populations where the dominant pollinators were syrphid flies, and flowering phenology was also subjected to stabilized quadratic selection. However, a later flowering start date was significantly selected at populations where the dominant pollinators were legitimate (normal pollination through the corolla tube entrance) and illegitimate bumblebees (abnormal pollination through nectar robbing hole which located at the corolla tube), and flowering phenology was subjected to disruptive quadratic selection. Wider corolla tube entrance diameter was selected at both populations. Furthermore, the strength of net directional selection on flowering start date and corolla tube entrance diameter was stronger at the population where the dominant pollinators were syrphid flies. Pollinator‐mediated selection explained most of the between‐population variations in the net directional selection on flowering phenology and corolla tube entrance diameter. Our results suggested the important influence of pollinator‐mediated selection on floral evolution. Variations in pollinator assemblages not only resulted in variation in the direction of selection but also the strength of selection on floral traits.     

Differentiation in a tropical deceptive orchid: colour polymorphism and beyond

Colour polymorphism has often been described among individuals of deceptive orchid species, and several studies have investigated reproductive success variations among colour morphs. However, whether colour morphs differed in other traits has received little attention in previous studies. Here, we report the case of a tropical deceptive orchid in Reunion Island that exhibits three different colour varieties. We investigated patterns of trait variation among colour varieties and found significant differences in floral and inflorescence morphology. Interestingly, we found that most populations included only individuals of a single variety, and that strong differences exist among varieties in spatial distribution and flowering phenology. This situation differs from previously reported cases of floral polymorphism in deceptive orchids where colour morphs co-occur and flower in the same populations. The spatio-temporal variation in flowering suggests that colour varieties have independent reproductive ecologies and are adapted to local conditions. We propose that potential variations in pollinator species abundance or diversity and the co-occurrence of nectar-producing species in the community may have driven the adaptation of each variety to its current pollination niche.     

Divergent selection on flowering phenology but not on floral morphology between two closely related orchids

Closely related species often differ in traits that influence reproductive success, suggesting that divergent selection on such traits contribute to the maintenance of species boundaries. Gymnadenia conopsea ss. and Gymnadenia densiflora are two closely related, perennial orchid species that differ in (a) floral traits important for pollination, including flowering phenology, floral display, and spur length, and (b) dominant pollinators. If plant–pollinator interactions contribute to the maintenance of trait differences between these two taxa, we expect current divergent selection on flowering phenology and floral morphology between the two species. We quantified phenotypic selection via female fitness in one year on flowering start, three floral display traits (plant height, number of flowers, and corolla size) and spur length, in six populations of G. conopsea s.s. and in four populations of G. densiflora. There was indication of divergent selection on flowering start in the expected direction, with selection for earlier flowering in two populations of the early‐flowering G. conopsea s.s. and for later flowering in one population of the late‐flowering G. densiflora. No divergent selection on floral morphology was detected, and there was no significant stabilizing selection on any trait in the two species. The results suggest ongoing adaptive differentiation of flowering phenology, strengthening this premating reproductive barrier between the two species. Synthesis: This study is among the first to test whether divergent selection on floral traits contribute to the maintenance of species differences between closely related plants. Phenological isolation confers a substantial potential for reproductive isolation, and divergent selection on flowering time can thus greatly influence reproductive isolation and adaptive differentiation.     

Impact of enhanced ultraviolet-B radiation on flower, pollen, and nectar production

Intensified ultraviolet-B radiation or UV-B (wavelengths between 280 and 320 nm) can delay flowering and diminish lifetime flower production in a few plants. Here we studied the effects of enhanced UV-B on floral traits crucial to pollination and pollinator reproduction. We observed simultaneous flowering responses of a new crop plant, Limnanthes alba (Limnathaceae), and a wildflower, Phacelia campanularia (Hydrophyllaceae), to five lifetime UV-B dosages ranging between 2.74 and 15.93 kJ·m·d. Floral traits known to link plant pollination with bee host preference, host fidelity and larval development were measured. Intensified UV-B had no overall effect on nectar and pollen production of L. alba and P. campanularia flowers. A quadratic relationship between UV-B and nectar sugar production occurred in P. campanularia and showed that even subambient UV-B dosages can be deleterious for a floral trait. Other floral responses to UV-B were more dramatic and idiosyncratic. As UV-B dosage increased, L. alba plants were less likely to flower, but suffered no delays in flowering or reductions to lifetime flower production for those that did flower. Conversely, an equal proportion of P. campanularia plants flowered under all UV-B treatments, but these same plants experienced delayed onset to bloom and produced fewer flowers at greater UV-B intensities. Therefore, intensified UV-B elicits idiosyncratic responses in flowering phenology and flower production from these two annual plants. Diurnal patterns in nectar and pollen production strongly coincided with fluctuating humidity and only weakly with UV-B dosage. Overall, our results indicated that intensified UV-B can alter some flowering traits that impinge upon plant competition for pollinator services, as well as plant and pollinator reproductive success.     

两种生境间大花百合不同性别表型开花及传粉特征的差异

植物的花期物候与花部综合特征均体现了其对生存环境的适应, 是与周围生物及非生物环境长期适应进化产生的结果。大花百合(Lilium concolor var. megalanthum)野外种群中具有雄性植株和两性植株两种不同性别表型。该研究以人为干扰较弱的孤山屯湿地以及人为干扰较强的金川湿地的大花百合为材料, 通过对两种生境间不同性别表型植株的花期物候、花部综合特征以及主要传粉昆虫的访花行为进行比较研究, 探究大花百合的开花及传粉特征在两种生境间的差异。结果表明: 孤山屯湿地内大花百合种群的始花期、盛花期、末花期均早于金川湿地。孤山屯湿地内大花百合的雄性植株在初开时花粉活力高于金川湿地, 而两种生境间的大花百合两性植株的花粉活力总体变化趋势一致。孤山屯湿地内大花百合雄性植株初开时的花蜜含量较高, 而后缓慢下降; 而在金川湿地内则是先增长, 48 h后开始下降。孤山屯湿地内大花百合两性植株的花蜜含量在开花24 h后开始下降, 金川湿地内则是48 h后才开始下降。孤山屯湿地内大花百合无论是雄性植株还是两性植株, 糖含量达到峰值的时间均比金川湿地晚。两种生境中大花百合两性植株的柱头可授性均保持较高水平。两种生境分布的大花百合主要传粉昆虫为中华蜜蜂(Apis cerana)、蓝灰蝶(Everes argiades)和老豹蛱蝶(Argyronome laodice)。孤山屯湿地内中华蜜蜂及蓝灰蝶对大花百合的访花频率均显著低于金川湿地, 但老豹蛱蝶的访花频率显著高于金川湿地。3种访花昆虫中, 中华蜜蜂的访花效率最高, 蓝灰蝶与老豹蛱蝶起到补充授粉的作用。两种生境间大花百合花期物候和花部综合特征的变化与当地小气候和传粉昆虫数量有关, 这种变化是大花百合经过长期适应而产生的。     

Divergence on floral traits and vertebrate pollinators of two endemic Encholirium bromeliads

Shifts in pollen vectors favour diversification of floral traits, and differences in pollination strategies between congeneric sympatric species can contribute to reproductive isolation. Divergence in flowering phenology and selfing could also reduce interspecific crossing between self‐compatible species. We investigated floral traits and visitation rates of pollinators of two sympatric Encholirium species on rocky outcrops to evaluate whether prior knowledge of floral characters could indicate actual pollinators. Data on flowering phenology, visitation rates and breeding system were used to evaluate reproductive isolation. Flowering phenology overlapped between species, but there were differences in floral characters, nectar volume and concentration. Several hummingbird species visited flowers of both Encholirium spp., but the endemic bat Lonchophylla bokermanni and an unidentified sphingid only visited E. vogelii. Pollination treatments demonstrated that E. heloisae and E. vogelii were partially self‐compatible, with weak pollen limitation to seed set. Herbivores feeding on inflorescences decreased reproductive output of both species, but for E. vogelii the damage was higher. Our results indicate that actual pollinators can be known beforehand through floral traits, in agreement with pollination syndromes stating that a set of floral traits can be associated with the attraction of specific groups of pollinators. Divergence on floral traits and pollinator assemblage indicate that shifts in pollination strategies contribute to reproductive isolation between these Encholirium species, not divergence on flowering phenology or selfing. We suggest that hummingbird pollination might be the ancestral condition in Encholirium and that evolution of bat pollination made a substantial contribution to the diversification of this clade.     

马先蒿属植物花冠分化与繁殖适应的研究进展

结合已有的研究报道和作者近年来的工作,对马先蒿属（Pedicularis）植物的花冠多样化成因与繁殖适应特性进行了总结和探讨。通过对该属4种进化花冠型的花器官发生和分化的研究发现,花部各器官在发生和发育初期基本一致,后期上唇形态的分化是导致成熟花形态结构产生较大差异的重要阶段。孢粉学研究认为,花冠类型与花粉萌发孔类型之间具有显著相关性;萌发沟的演化可能与繁殖适应有一定的关系。分子系统学研究表明,多样化的花冠类型在不同的谱系内经过若干次的独立进化而表现出了高度的平行演化（parallelism）。传粉生物学研究证实,该属植物花冠多样化与其主要传粉者熊蜂属（Bombus）昆虫的传粉行为存在较为密切的关系。具有相同（似）花冠类型的马先蒿可能被同种或不同种的熊蜂以相同的方式访问,但在花粉落置位置上存在显著差异,这可能有助于同域分布重叠的物种间在生殖上的机械隔离,而花冠的分化在一定程度上促进了新的物种形成。     

Association between rainfall seasonality and the flowering of epiphytic plants in a Neotropical montane forest

The association between the reproductive phenology of epiphytic communities with environmental and ecological factors remains largely unexplored. Because epiphytes depend on environmental moisture, seasonal changes in moisture conditions likely act as the primary determinants of their reproductive timing. We examined whether water limitation or pollinator competition structures the flowering phenologies of an epiphytic community in a seasonal mountain forest in Costa Rica. Additionally, we addressed the environmental factors that might trigger floral induction. Using a 24‐month dataset of bimonthly flowering records from 104 species, we found high seasonality of flowering at the species level but somewhat lower seasonality at the community level. The flowering mid‐dates of most epiphytes, particularly from monocotyledonous species, occurred during the wettest months, as predicted if water limitation structures flowering. The increased moisture and nutrient availability during the rainy season give epiphytes the resources needed to complete floral development and anthesis, and later fruit and seed maturation. The observed flowering pattern of epiphytes coincides with reproductive patterns of terrestrial herbs and shrubs from seasonal tropical ecosystems, and suggests shared constraints to sexual reproduction in both ecological guilds under similar climatic conditions. In contrast, flowering patterns of congeneric epiphytes in the same pollination guild mostly did not follow the expectations of a pollinator competition scenario. Finally, we discuss the possible combined effect of precipitation, temperature, and daily insolation on floral induction of epiphytic plants.     

Changes in Florets’ Vertical Direction within Inflorescence Affects Pollinator Behavior,and Fitness in <i>Trifolium repens</i>

Ecological interactions between flowers and pollinators greatly affect the reproductive success. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission, flower rewards and floral vertical direction, in a rhythmic fashion. However, less is known about how plants regulate the relationship between these flower traits to adapt to pollinator visiting behavior and increase reproduction success. Here we investigated the adaptive significance of the flower bending from erect to downward in Trifolium repens. We observed the flowering dynamic characteristics (changes of vertical direction of florets, flowering number, pollen grain numbers, pollen viability and stigma receptivity over time after blossom) and the factors affecting the rate of flower bending in T. repens. Then we altered the vertical direction of florets in inflorescence of different types (upright and downward), and compared the pollinator behaviors and female reproductive success. Our results showed that florets opened sequentially in inflorescence, and then bend downwards slowly after flowering. The bending speed of florets was mainly influenced by pollination, and bending angle increased with the prolongation of flowering time, while the pollen germination rate, stigma receptivity and nectar secretion has a rhythm of “low-high-low” during the whole period with the time going. The visiting frequency of all the four species of pollinators on upward flowers was significantly higher than that of downward flowers, and they especially prefer to visit flowers with a bending angle of 30°–60°, when the flowers was exactly of the highest flower rewards (nectar secretion and number of pollen grains), stigma receptivity and pollen germination rate. The seed set ratio and fruit set ratio of upward flowers were significantly higher than downward flowers, but significantly lower than unmanipulated flowers. Our results indicated that the T. repens could increase female and male fitness by accurate pollination. The most suitable flower angle saves pollinators’ visiting energy and enables them to obtain the highest nectar rewards. This coordination between plants and pollinators maximizes the interests of them, which is a crucial factor in initiating specialized plant-pollinator relationships.     

Individual flowering phenology shapes plant–pollinator interactions across ecological scales affecting plant reproduction

The balance of pollination competition and facilitation among co-flowering plants and abiotic resource availability can modify plant species and individual reproduction. Floral resource succession and spatial heterogeneity modulate plant–pollinator interactions across ecological scales (individual plant, local assemblage, and interaction network of agroecological infrastructure across the farm). Intraspecific variation in flowering phenology can modulate the precise level of spatio-temporal heterogeneity in floral resources, pollen donor density, and pollinator interactions that a plant individual is exposed to, thereby affecting reproduction. We tested how abiotic resources and multi-scale plant–pollinator interactions affected individual plant seed set modulated by intraspecific variation in flowering phenology and spatio-temporal floral heterogeneity arising from agroecological infrastructure. We transplanted two focal insect-pollinated plant species (Cyanus segetum and Centaurea jacea, n = 288) into agroecological infrastructure (10 sown wildflower and six legume–grass strips) across a farm-scale experiment (125 ha). We applied an individual-based phenologically explicit approach to match precisely the flowering period of plant individuals to the concomitant level of spatio-temporal heterogeneity in plant–pollinator interactions, potential pollen donors, floral resources, and abiotic conditions (temperature, water, and nitrogen). Individual plant attractiveness, assemblage floral density, and conspecific pollen donor density (C. jacea) improved seed set. Network linkage density increased focal species seed set and modified the effect of local assemblage richness and abundance on C. segetum. Mutual dependence on pollinators in networks increased C. segetum seed set, while C. jacea seed set was greatest where both specialization on pollinators and mutual dependence was high. Abiotic conditions were of little or no importance to seed set. Intra- and interspecific plant–pollinator interactions respond to spatio-temporal heterogeneity arising from agroecological management affecting wild plant species reproduction. The interplay of pollinator interactions within and between ecological scales affecting seed set implies a co-occurrence of pollinator-mediated facilitative and competitive interactions among plant species and individuals.     

IS FLORAL SPECIALIZATION AN EVOLUTIONARY DEAD‐END? POLLINATION SYSTEM TRANSITIONS IN RUELLIA (ACANTHACEAE)

Pollination systems frequently reflect adaptations to particular groups of pollinators. Such systems are indicative of evolutionary specialization and have been important in angiosperm diversification. We studied the evolution of pollination systems in the large genus Ruellia. Phylogenetic analyses, morphological ordinations, ancestral state reconstructions, and a character mapping simulation were conducted to reveal key patterns in the direction and lability of floral characters associated with pollination. We found significant floral morphological differences among species that were generally associated with different groups of floral visitors. Floral evolution has been highly labile and also directional. Some specialized systems such as hawkmoth or bat pollination are likely evolutionary dead-ends. In contrast, specialized pollination by hummingbirds is clearly not a dead-end. We found evidence for multiple reverse transitions from presumed ancestral hummingbird pollination to more derived bee or insect pollination. These repeated origins of insect pollination from hummingbird-pollinated ancestors have not evolved without historical baggage. Flowers of insect-pollinated species derived from hummingbird-pollinated ancestors are morphologically more similar to hummingbird flowers than they are to other more distantly related insect-pollinated flowers. Finally, some pollinator switches were concomitant with changes in floral morphology that are associated with those pollinators. These observations are consistent with the hypothesis that some transitions have been adaptive in the evolution of Ruellia.     

Floral isolation is the main reproductive barrier among closely related sexually deceptive orchids

Floral isolation is an important component of pollinator-driven speciation. However, up to now, only a few studies have quantified its strength and relative contribution to total reproductive isolation. In this study, we quantified floral isolation among three closely related, sympatric orchid species of the genus Ophrys by directly tracking pollen flow. Ophrys orchids mimic their pollinators' mating signals, and are pollinated by male insects during mating attempts. This pollination system, called sexual deception, is usually highly specific. However, whether pollinator specialization also conveys floral isolation is currently under debate. In this study, we found strong floral isolation: among 46 tracked pollen transfers in two flowering seasons, all occurred within species. Accounting for observation error rate, we estimated a floral isolation index ≥0.98 among each pair of species. Hand pollination experiments suggested that postpollination barriers were effectively absent among our study species. Genetic analysis based on AFLP markers showed a clear species clustering and very few F(1) hybrids in natural populations, providing independent evidence that strong floral isolation prevents significant interspecies gene flow. Our results provide the first direct evidence that floral isolation acts as the main reproductive barrier among closely related plant species with specialized pollination.     

The pollination niche and its role in the diversification and maintenance of the southern African flora

The flora of southern Africa has exceptional species richness and endemism, making it an ideal system for studying the patterns and processes of evolutionary diversification. Using a wealth of recent case studies, I examine the evidence for pollinator-driven diversification in this flora. Pollination systems, which represent available niches for ecological diversification, are characterized in southern Africa by a high level of ecological and evolutionary specialization on the part of plants, and, in some cases, by pollinators as well. These systems are asymmetric, with entire plant guilds commonly specialized for a particular pollinator species or functional type, resulting in obvious convergent floral evolution among guild members. Identified modes of plant lineage diversification involving adaptation to pollinators in these guilds include (i) shifts between pollination systems, (ii) divergent use of the same pollinator, (iii) coevolution, (iv) trait tracking, and (v) floral mimicry of different model species. Microevolutionary studies confirm that pollinator shifts can be precipitated when a plant species encounters a novel pollinator fauna on its range margin, and macroevolutionary studies confirm frequent pollinator shifts associated with lineage diversification. As Darwin first noted, evolutionary specialization for particular pollinators, when resulting in ecological dependency, may increase the risk of plant extinction. I thus also consider the evidence that disturbance provokes pollination failure in some southern African plants with specialized pollination systems.     

马先蒿属花冠形态的多样性与传粉式样的关系

马先蒿属(Pediculais)是有花植物中花冠形态多样化最为集中的属。该属主要的传粉者是熊蜂属(Bormbus)昆虫;在北美,熊蜂和蜂鸟是马先蒿植物一些种类有效的传粉者;也发现壁蜂(Osmia)为其传粉。不同的传粉机制要求某一特定的取食式样储藏和释放花粉。本文讨论了花冠类型的进化趋势与传粉式样和花粉形态的关系。传粉者的选择压力是决定花冠多样化的重要因素之一;花冠类型与传粉者和传粉行为紧密相关。马先蒿植物和传粉者的相互依赖与其花冠类型、功能和物候互相适应,但花冠类型与花粉形态两者之间似乎没有明显的一一对应关系。通过北美、日本和喜马拉雅不同地理分布马先蒿种类的比较研究表明,具有相同花冠类型的种类有着相同的传粉方式,花冠形态与传粉式样存在紧密的协同进化关系。     

The pollination ecology of Paraboea rufescens (Gesneriaceae): a buzz-pollinated tropical herb with mirror-image flowers

BACKGROUND AND AIMS: Gesneriaceae is a pantropical plant family with over 3000 species. A great variety of pollination mechanisms have been reported for the neotropical members of the family, but the details of buzz-pollination and enantiostyly for the family have not been described. We investigated the floral biology and pollination ecology of Paraboea rufescens in Xishuangbanna, south-west China, considering three aspects: (1) the type of enantiostyly exhibited; (2) whether the species is self-compatible; and (3) whether pollinator behaviour could enhance the precision of pollen transfer between flowers of contrasting stylar orientation. METHODS: Flowering phenology was monitored once a month during vegetative growth, and once a week during flowering both in the field and under cultivation. Pollination manipulations and pollinator observation in the field were conducted. KEY RESULTS: Anthesis occurred early during the morning, and flowers remained open for 1-5 d, depending on weather conditions. Controlled pollinations revealed that P. rufescens is self-compatible, and exhibited inbreeding depression in seed set. Plants were pollinator limited in natural populations. The similar stylar deflection among flowers within a plant limits autonomous self-pollination as well as pollination between flowers. Two species of bumble bees (Bombus spp.), Amegila malaccensis and Nomia sp. effectively pollinated P. rufescens. These pollinators visited flowers in search of pollen with almost the same frequency. None of the pollinators appeared to discriminate between left- or right-handed flowers. CONCLUSIONS: Paraboea rufescens exhibits monomorphic enantiostylous flowers and a buzz-pollination syndrome. Floral morphology in P. rufescens and pollinator foraging behaviour seems likely to reduce self-pollination and pollinations between flowers of the same stylar deflection.     

鼠尾草属不同物种的雄蕊杠杆机制对传粉者空间变异的进化响应

被子植物虫媒传粉植物的物种分化通常被认为是花性状响应传粉环境(传粉者)的空间变异而发生适应性分化的结果。通过对鼠尾草属(Salvia) 3个物种(共4个居群)传粉互作系统的比较, 探索了花性状对不同传粉环境的进化响应。结果表明: 各居群的传粉者组成、主要传粉者类型及其大小各不相同, 杠杆状雄蕊及相关花部性状大小在不同居群间具有显著差异; 各居群均表现出腹部传粉和背部传粉2种传粉模式, 但背部传粉仍然是最有效的传粉方式; 居群间杠杆状雄蕊长度与传粉者体长表现出极显著的正相关, 然而花冠长与传粉者体长表现出负相关; 花冠口高度和柱头高度与传粉者胸厚也表现出一定的协同变异。鼠尾草属植物的杠杆状雄蕊及相关花部性状在传粉系统的进化过程中表现出高度的可塑性, 表明雄蕊杠杆传粉机制对传粉环境的变异非常敏感, 在该属植物的物种分化过程中具有关键作用。     

Highly efficient pollination by bumblebees ensures seed production in Pedicularis lachnoglossa (Orobanchaceae), an early‐flowering Himalayan plant

Abstract Pedicularis (Orobranchaceae) is a common high altitude genus of the Himalayas that may be affected by pollination limitation. Using Pedicularis lachnoglossa from Yulong (Jade Dragon) Snow Mountain in Lijiang (Yunnan Province, southwest China), we investigated the effects of high altitude habitats on the process of pollination and seed production. Floral biology, pollinator foraging behavior, breeding system, and pollination efficiency were examined using observation and exclusionary techniques. Pedicularis lachnoglossa was found to be entomophilous and exclusively pollinated by Bombus friseanus and B. yunnanicola. Our results indicated that pollination limitation in P. lachnoglossa was not significant. Under open pollination, approximately 80% of flowers were successfully pollinated and developed to fruits, and about 38% of ovules developed to mature seeds. Bumblebee pollination is highly precise and efficient in P. lachnoglossa, because its flowering phenology and floral characters enhance the foraging of bumblebees on flowers. This study supports that animal pollination plays a crucial role in the outbreeding of the early flowering Pedicularis. The evolution of floral specification in Pedicularis has the advantages of adaptation to bumblebee pollination in adverse high altitude habitats.