Attracting pollinators and avoiding herbivores: insects influence plant traits within and across years

Perennial plants interact with herbivores and pollinators across multiple growing seasons, and thus may respond to herbivores and pollinators both within and across years. Joint effects of herbivores and pollinators influence plant traits, but while some of the potential interactions among herbivory, pollination, plant size, and plant reproductive traits have been well studied, others are poorly understood. This is particularly true for perennial plants where effects of herbivores and pollinators may manifest across years. Here, we describe two experiments addressing the reciprocal interactions of plant traits with herbivore damage and pollination across 2 years using the perennial plant Chamerion angustifolium. We measured (1) plant responses to manipulation of damage and pollination in the year of treatment and the subsequent season, (2) damage and pollination responses to manipulation of plant size and flowering traits in the year of treatment, and (3) plant-mediated indirect interactions between herbivores and pollinators. We found that plant traits had little effect on damage and pollination, but damage and pollination affected plant traits in both the treatment year and the subsequent year. We found evidence of indirect effects between leaf herbivores and pollinators in both directions; indirect effects of pollinators on leaf herbivores have not been previously demonstrated. Our results indicate that pollen receipt results in shorter plants with fewer stems but does not change flower number, while leaf herbivory results in taller plants with fewer flowers. Together, herbivory and pollination may contribute to intermediate plant height and plants with fewer stems and flowers in our system.     

Floral traits and mating system of Hibiscus trionum (Malvaceae)

Variations in floral traits and floral structures influence plant mating systems. Hibiscus trionum produces large, showy flowers typical of an outcrossing species, yet flowers are autonomously self-pollinated. In this study, we measured floral morphology, breeding system and outcrossing rate estimated by ISSR markers. Results indicate that two types of flowers were observed in H. trionum, and the type I with bigger petals appears to be much more visible to pollinators, demonstrated by than type II flowers with smaller petals. The flowers with hand pollination were closed 1 h earlier than intact flowers, whether they were type I or II. The relationship between the amount of pollen deposited on the stigma and the number of seeds per capsule was highly significant, and 80 or more pollens per flower can make the mean number of seeds (mean = 37) in H. trionum. Delayed selfing in H. trionum did not provide a large contribution to seed production, since reproductive assurance were only 0.025. However, successful reproduction of 72.5% flowers in the absence of pollinators suggested that selfing provides reproductive assurance during seasons, in which pollinators were limiting. The multilocus outcrossing rates in different populations varied from 0.982 to 1.200, with a mean of 1.116. Our data provide an empirical demonstration of a predominantly outcrossing species with potential delayed selfing when pollinators are absent or scarce.     

Reproductive biology of an alpine orchid Phaius delavayi

The genus Phaius is distributed mainly in pantropical areas, and most species reported are autogamous. In contrast, Phaius delavayi, an alpine plant endemic to temperate zones of China, is strictly pollinator dependent. Only female workers and males of the bumblebee species B. hypnorum and B. lepidus are effective pollinators. The pollinaria are deposited on top of the head or the prothorax of the pollinators. The different depositions of pollinaria are regarded as an adaptation of the chamber dimensions of the flower to the size of the pollinator. The natural fruit set reported here (24.6–37.1%) suggests that pollination is successful in the deceptive P. delavayi. The yellow perianth and sweet floral scent of P. delavayi are important cues in attracting pollinators, while flowering time and mass population are associated with the process of “learning and avoidance” of the rewardless flowers. This orchid, therefore, employs a deceptive pollination strategy with diverse pollinators and pollinaria depositions rather than autogamy as do its congeners.     

钝叶柃不同性别花的花部形态与传粉特征比较

据有关资料记载,柃属(Eurya Thunb.)植物属于雌雄异株植物,目前仅在柃木(Eurya japonica Thunb.)中有过两性花的报道。近年的调查发现,钝叶柃(Eurya obtusifolia H.T.Chang)也有性别变异,存在两性花。在对其性别特征及功能研究的基础上,进一步跟踪了钝叶柃的开花和传粉过程,对不同性别花的花部形态和传粉特征进行了比较分析。在重庆市北碚区选取了4个样地,测定了花部形态、花朵朝向、花粉活力、柱头可授性、花粉对水的耐受性、单花花粉量和单花泌蜜体积等形态和传粉相关指标,并对其开花动态、传粉昆虫种类和昆虫传粉行为进行了仔细观察,还进行了套袋试验。结果发现钝叶柃不同性别花的花部形态和传粉特征既有一些共同点,又存在着明显差异,性别变异株则呈现出雌雄植株间的过渡特征。钝叶柃是一种花期短,花小而多,开花同步性高的植物,雌花和雄花色味相同。该植物的主要传粉方式为虫媒,主要传粉者为两种蜜蜂科昆虫,但风媒也在其传粉中起着一定作用。该植物不同性别花的主要差异有:1)雄花呈灯笼状,花瓣不反卷,雌花辐射状,花瓣反卷;2)雄花较雌花大;3)雄花倾向于垂直朝下,雌花倾向于斜向下朝向枝条末端;4)雌花寿命较雄花长。钝叶柃在开花和传粉上的许多特征都在一定程度上体现了其对雌雄异株性系统的适应。相应地,传粉者在不同性别植株上的行为也存在一定差异。钝叶柃不同性别花在形态上的差异是其周围各种生物因素及非生物因素共同作用的结果,其中传粉昆虫和雨水的选择可能在这些差异的塑造中起着重要作用。     

Can floral consumption by fish shape traits of seagrass flowers?

Seagrasses are marine flowering plants with hydrophilous pollination. This abiotic pollination by water assumes absence of flower-animal interaction, but animals can interfere in this process through consumption of reproductive structures. We studied predation on male flowers by fish for three dioecious seagrass species (Thalassia testudinum, Syringodium filiforme and Halodule wrightii) in the Mexican Caribbean. Seagrass flowers have a highly reduced or absent corolla and florivores directly consumed the anthers with pollen. The foliar structures (tepals, bracts or sheaths) protecting the male flower buds were removed by hand in situ. The floral buds were followed by videos or taking pictures at regular intervals and most (56–100 %, depending on seagrass species and experimental setting) artificially denuded male flower buds were consumed within 24 h by juvenile fish of various species. Histochemical analysis showed that the pollen and embedding mucilage were rich in polysaccharides and proteins, thus potentially nutritious. The seagrasses had copious production of pollen (between 0.2 and 1.2 × 10⁶ pollen per flower, depending on the species). But T. testudinum and S. filiforme were often pollen limited, and the probability of fruit set was reduced ~50 % when the females were at the distance of 1 and 5–6 m from the males flowers, respectively. Under natural conditions, depredation on pre-anthesis male flowers in the three species was low because flower bud emergence (few hours) and pollen release (1–4 h) were ephemeral processes. In addition, the release of pollen of T. testudinum occurred at dusk when herbivorous fish became inactive. These life-cycle characteristics aid to avoid excessive pollen consumption by fish, however, whether they are anti-predator strategies or mere adaptations for submarine pollination remains to be established.     

Pterandra pyroidea: a case of pollination shift within neotropical Malpighiaceae

Background and Aims

Most Neotropical species of Malpighiaceae produce floral fatty oils in calyx glands to attract pollinating oil-collecting bees, which depend on this resource for reproduction. This specialized type of pollination system tends to be lost in members of the family that occur outside the geographic distribution (e.g. Africa) of Neotropical oil-collecting bees. This study focused on the pollination ecology, chemical ecology and reproductive biology of an oil flower species, Pterandra pyroidea (Malpighiaceae) from the Brazilian Cerrado. Populations of this species consist of plants with oil-secreting (glandular) flowers, plants with non-oil-secreting flowers (eglandular) or a mix of both plant types. This study specifically aims to clarify the role of eglandular morphs in this species.

Methods

Data on pollinators were recorded by in situ observations. Breeding system experiments were conducted by isolating inflorescences and by enzymatic reactions. Floral resources, pollen and floral oils offered by this species were analysed by staining and a combination of various spectroscopic methods.

Key Results

Eglandular flowers of P. pyroidea do not act as mimics of their oil-producing conspecifics to attract pollinators. Instead, both oil-producing and oil-free flowers depend on pollen-collecting bees for reproduction, and their main pollinators are bumble-bees. Floral oils produced by glandular flowers are less complex than those described in closely related genera.

Conclusions

Eglandular flowers represent a shift in the pollination system in which oil is being lost and pollen is becoming the main reward of P. pyroidea flowers. Pollination shifts of this kind have hitherto not been demonstrated empirically within Neotropical Malpighiaceae and this species exhibits an unusual transition from a specialized towards a generalized pollination system in an area considered the hotspot of oil-collecting bee diversity in the Neotropics. Transitions of this type provide an opportunity to study ongoing evolutionary mechanisms that promote the persistence of species previously involved in specialized mutualistic relationships.     

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.     

Some pollination strategies in neotropical savannas and forests

Previously published data on flowering phenology and pollination of neotropical families are reviewed and compared with new observations, in order to evaluate some trends of pollination strategies in neotropical savannas and forests. Central American forestBignoniaceae apparently diminish competition between sympatric species with identical pollination strategies by alternating flowering. On the other hand, in theBignoniaceae of Brazilian cerrado savannas coincident flowering is more common, suggesting different pollination strategies. Bees specialized in nectar robbery are associated withBignoniaceae, particularly mass-flowering species. These nectar robbers stimulate pollinator movements between flowers and thus increase pollen-flow. The flowering phenology of theMalpighiaceae from forests and savannas apparently follows the phenology of theAnthophorinae (mainlyCentridini)-bees, on which this plant group almost exclusively depends for pollination in the Neotropics. As the flowers of different genera and species are very uniform, the bees quite indiscriminately pollinate coexistingMalpighiaceae taxa. In theMalvaceae, the more primitive tree or shrub habit and an allogamous reproduction system is quite significantly associated with an ornithophilous pollination mode. Hummingbirds in the Neotropics have probably influenced the origin of the primitive bird-pollinatedMalvaceae flower. In conjunction with the diversification of theMalvaceae and their migration into more open regions, pollination by bees has apparently become more prominent. ChiropterophilousMalvaceae seem to have developed more recently from ornithophilous ancestors within the neotropical forest regions. As a result of this ecological radiation, parallel modifications of the basic ornithophilous flower principle can be traced in different groups of theMalvaceae. Dynastinae-beetles are pollinators of South and Central American species ofAnnona, Cymbopetalum, Caladium, Talauma, Philodendron, Victoria, Nymphaea, Cyclanthus, Bactris and others. In many cases the relationship between flowers and theirDynastinae visitors is not very specific, principally reflecting differences in the faunistic spectrum of diverse regions and vegetation types. The attraction of these beetles as flower visitors in several unrelated groups of Angiosperms must have occurred repeatedly. It is suggested that the flower visiting species of this beetle group may have acquired their preference for certain pungent or aromatic flower odours by their feeding habits during the larval stage.     

Pollination ecology in sympatric winter flowering Helleborus (Ranunculaceae)

We studied biotic and abiotic factors that influence pollination in two sympatric winter flowering species. Helleborus foetidus and Helleborus bocconei flower simultaneously in winter. Although climatic conditions are not favorable for biotic pollination both species rely mainly on large bees of the genus Bombus. At the beginning of flowering, harsh climatic conditions are restrictive for insect visits. As flowering continues and temperatures rise, pollinator activity increases. The two plant species share pollinators that visit them indiscriminately. The flowers of the two species differ in form and insects visit H. foetidus by inserting their heads and H. bocconei ventrally: pollen load on insects is highly specialized. With the arrival of spring, many other species start to bloom and in spite of the large number of flowers still on the plants insects abandon Helleborus species. At the end of spring increasing biotic interactions take away pollinators from the Helleborus species.     

Reproductive ecology of the carnivorous plant Pinguicula moranensis (Lentibulariaceae)

• The interaction of plants with pollinators can be a determinant of their reproductive fitness. However, information about the pollination biology of carnivorous plants is scarce. To increase knowledge of reproductive ecology of carnivorous plants we focused on Pinguicula moranensis. Specifically, based on the presence of large, zygomorphic and spurred flowers, we predicted higher reproductive fitness in cross‐pollinated than in self‐pollinated flowers.
• Within a plot of 51 m² we characterised the reproductive phenology, including flower lifespan and stigmatic receptivity. We identified pollinators and their movement patterns within the plot. Breeding system was experimentally evaluated using hand‐pollination (i.e. autonomous, self‐ and cross‐pollination).
• Flowers of P. moranensis were visited by long‐tongued pollinators, mainly members of the Lepidoptera. Hand‐pollination experiments confirmed our prediction and suggest that flower traits might favour cross‐pollination.
• We mainly discuss the implications of the patchy distribution of plants and behaviour of pollinators on gene movement in this plant species, as pollination between genetically related individuals could be occurring.

     

Floral biology and pollination in Cucumis melo L., a tropical andromonoecious cucurbit

We studied floral biology and the role of flower visitors in fruit set of muskmelon (Cucumis melo L.). Muskmelon produced Staminate (hereafter ‘S’) and Hermaphrodite (hereafter ‘H’) flowers with a ratio of 18:1. Flowers opened around 40 days after planting and flowering continued for another 40 days. Longevity of both types of flowers was one day. Anthesis in S flowers was earlier (0545–0700 h) than that of H flowers (0700–0830 h). Anther dehiscence occurred 10–15 min after anthesis in both the flowers. The number of pollen grains in H flowers was significantly lower (2715 ± 143) than S flowers (4968 ± 398). Pollen viability and stigma receptivity was maximum between 1600 and 1800 h. The pollen tube of pollen grains from H flowers grew very slowly and never reached the ovary. There were two peaks in nectar production in a day (1000–1200 h and 1400–1800 h). Sixteen species of insects belonging to Hymenoptera (81.25%), Diptera (12.50%) and Lepidoptera (6.5%) visited muskmelon flowers. Major visitors were honeybees, Apis cerana F. and A. florea F. and both were efficient pollinators. Diversity and abundance of flower visitors positively correlated with floral abundance. In pollination exclusion experiments, no fruit set was observed in bagged, self-pollinated and the flowers artificially crossed only with other H pollen. But, those flowers hand pollinated with pollen from S flowers and ones that were allowed for open pollination set maximum fruits. The crop needs a minimum of 8–10 bee visits per flower to achieve the same level of pollination efficiency provided with natural/unrestrained visits.     

<Emphasis Type="Italic">Apis mellifera</Emphasis> and <Emphasis Type="Italic">Osmia cornuta</Emphasis> as carriers for the secondary spread of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> on apple flowers

The efficiency of two pollinators, Apis mellifera L. (Hymenoptera: Apidae) and the mason bee Osmia cornuta (Latreille) (Hymenoptera: Megachilidae), as carriers of biocontrol agents (BCA) from flower to flower (secondary colonisation) was investigated on apple cv ‘Golden Delicious’. The BCA tested was Bacillus subtilis, strain BD170 (Biopro®) developed for the control of the ‘fire blight’ caused by Erwinia amylovora (Burril) Winslow et al. The two insect species were studied as secondary BCA carriers on apple plants in pots under net screened tunnels. Their behaviour and capacity to deposit the BCA in the most receptive flower parts were compared both by washing, diluting and plating the flower organs on a recovery medium and by means of PCR analyses based on a molecular marker. O. cornuta showed better performances with respect to A. mellifera. For the field trials, pollinators were introduced in four apple orchards. During apple’s flowering, the BD170 (100 g hl^?l) was sprayed once in two fields, and twice in the others. The pollinators’ efficacy in carrying the BCA from sprayed flowers to the stigmas of newly opened ones at different times after the spray treatment was evaluated. The detection of the BCA was performed by PCR analysis. The percentages of positive PCR flower samples were higher in the internal treated areas of the fields with respect to the external untreated ones, but the high colonisation level found in the latter and in the flowers opened in both areas several days after the treatment(s) demonstrated that pollinators can play an important role as secondary carriers.     

沙丘稀有种准噶尔无叶豆花部综合特征与传粉适应性

植物花部特征进化与传粉适应性一直是进化生态学领域关注的核心问题之一。以古尔班通古特沙漠自然生长的准噶尔无叶豆为对象,对其花部特征和传粉特性进行了野外观察和室内的分析研究。结果表明:种群花期历时21 d,花序花期历时7-12 d,单花花期一般3 d,若遇阴雨天气,花期可延长1-2 d,整个花期龙骨瓣一直保持闭合状态。单花10枚花药在旗瓣微张时已全部完成散粉。准噶尔无叶豆主要靠分泌花蜜、鲜艳的花色以及旗瓣基部的黄色辐射状纹理结构吸引传粉者。准噶尔无叶豆花期的有效传粉者为4种蜂类昆虫,它们的平均访花频率为(7.75±0.57)次·花^-1·d^-1,访花高峰期表现为三峰型: 13:00-14:00,16:00-17:00和19:00-20:00。准噶尔无叶豆人工套袋实验表明该种为自交亲和型,主动自交少见,生殖成功依赖传粉者。胚珠成功受精至果实完全成熟阶段存在自交衰退,柱头角质层结构和花粉刷结构是准噶尔无叶豆在进化过程中形成的减少自交,倾向异交的机制。     

Nectar ecology of Datura ferox (Solanaceae): an invasive weed with nocturnal flowers in agro-ecosystems from central Argentina

Plant–pollinator interactions provide highly important ecological functions, and are influenced by floral nectar characteristics. The night blooming Datura ferox is an excellent model to test general hypotheses on the relationship between nectar traits (e.g., nectar secretion patterns, nectar chemical composition), pollinators and reproductive success for invasive, weedy species in highly modified ecosystems as crop fields. We hypothesized an adjustment between nectar composition and secretion dynamics through flower anthesis and the activity and requirements of nocturnal pollinators. Nectar chemical analyses showed low quantities of amino acids and lipids, phenolics, and alkaloids were not detected. D. ferox showed sucrose-dominant nectar with comparable amount of hexoses. Sugar proportions did not vary between populations or during flowering season. Most nectar is secreted before flower opening. Nectar resorption was detected at the end of anthesis. Experimentally drained flowers of both populations increased nectar production up to 50 % in the total amount of sugar per flower compared to control flowers. Nectar standing crop was relatively constant during the flowering season, but differences were detected between populations. Nectar traits of D. ferox would be favoring cross-pollination and maintaining seed production of this weed, since recently open flowers display a higher amount of nectar and they can renew nectar after a pollinator visit or reabsorb it at the end of anthesis. This nectar source may be important for native pollinators considering that human-induced forest fragmentation is related with the impoverishment of native flora from agro-ecosystems.     

Intraseasonal variation in pollination intensity and seed set in an alpine population of Ranunculus acris in southwestern Norway

I studied aspects of the pollination and reproduction ecology of an alpine population of the circurnpolar Ranunculus acris (Ranunculaceae) at Hardangervidda, southwest Norway Dipteran families, mainly Muscidae and Anthomyudae, were the most frequent flower visitors and pollinators A single visit by these insects resulted in a seed set of c 18% of the total potential Visitation rates were highest early m the flowering season The longevity of individual flowers of early flowering plants was c 3 d shorter than that of mid-season flowering individuals Insect pollinators moved short distances between flowers and they mostly visited near neighbour plants Expenments showed that Ranunculus acris was self-incompatible and thus dependent on insect visitation for seed production Early flowering individuals had a very high seed set relative to individuals flowering in mid- and late season, suggesting a strong selection pressure for early flowering in the population Seed production in this Ranunculus acris population seems to be limited by severe climatic conditions and a low pollination intensity     

Domestication of cardamom (Elettaria cardamomum) in Western Ghats, India: divergence in productive traits and a shift in major pollinators

Background and Aims

Elettaria cardamomum, a highly priced spice, is native to the Western Ghats of South India. Wild populations still occur in isolated patches in their natural habitats; however, much of today''s commercial product comes from cultivated sources. There is no information on domestication-related traits of this species; the main objective of this study was to compare wild and cultivated populations of cardamom in terms of vegetative and reproductive features in order to identify domestication syndromes and to examine whether the two populations have developed reproductive barriers.

Methods

Two wild populations and five cultivated plantations were used for the present study. Vegetative and floral traits, flowering phenology, pollination biology and breeding systems of wild and cultivated populations were compared. Effective pollinators amongst floral visitors were identified by confirming pollen transfer as well as by fruit set following their visit to virgin flowers. Manual pollinations were carried out in order to study the breeding systems of the two populations and reproductive barriers, if any, between them.

Key Results

Several productive traits including the number of branches, number of inflorescences, and total number of flowers per clump, number of flowers that open each day, the duration of flowering, the length of the flower and the amount of nectar per flower are significantly greater in cultivated cardamom. The principal pollinators in wild cardamom are solitary bees, Megachile sp. and two species of Amegilla, whereas those in cultivated cardamom are the social bees Apis dorsata, A. cerana and Trigona iridipennis. Both the wild and cultivated populations are self-compatible and there are no reproductive barriers between the two populations.

Conclusions

Domestication in cardamom has brought about significant changes in vegetative and reproductive traits and a shift in effective pollinators from native solitary bees to social bees. The shift in pollinators seems to be due to the availability of a large number of flowers for prolonged periods in cultivated cardamom that can attract and sustain social bees, rather than due to co-evolution of the flower and the pollinator.Key words: Elettaria cardamomum, wild cardamom, domestication, Amegilla sp., Apis cerana, Apis dorsata, Megachile sp., pollination efficiency, solitary bees, social bees     

Stigmatic fluid aids self-pollination in Roscoea debilis (Zingiberaceae): a new delayed selfing mechanism

Background and Aims

Delayed selfing is the predominant mode of autonomous self-pollination in flowering plants. However, few delayed selfing mechanisms have been documented. This research aims to explore a new delayed selfing mechanism induced by stigmatic fluid in Roscoea debilis, a small perennial ginger.

Methods

Floral biology and flower visitors were surveyed. The capacity of autonomous selfing was evaluated by pollinator exclusion. The timing of autonomous selfing was estimated by emasculation at different flowering stages. The number of seeds produced from insect-pollination was assessed by emasculation and exposure to pollinators in the natural population. The breeding system was also tested by pollination manipulations.

Key Results

Autonomous self-pollination occurred after flowers wilted. The stigmatic fluid formed a globule on the stigma on the third day of flowering. The enlarged globule seeped into the nearby pollen grains on the fourth flowering day, thus inducing pollen germination. Pollen tubes then elongated and penetrated the stigma. Hand-selfed flowers produced as many seeds as hand-crossed flowers. There was no significant difference in seed production between pollinator-excluded flowers and hand-selfed flowers. When emasculated flowers were exposed to pollinators, they produced significantly fewer seeds than intact flowers. Visits by effective pollinators were rare.

Conclusions

This study describes a new form of delayed autonomous self-pollination. As the predominant mechanism of sexual reproduction in R. debilis, delayed self-pollination ensures reproduction when pollinators are scarce.     

火把花的繁殖生物学研究

火把花（Colquhounia coccinea?）表现出典型的鸟媒综合征,因此具有作为引鸟景观植物的开发潜力。以自然、人工生境的火把花居群为研究对象,通过观察和试验对其开花物候、花部综合特征、访花动物及其行为、繁育系统、种子萌发特性进行研究,以明确火把花的繁殖特性及对不同访花动物的吸引潜力。结果显示,火把花的整体花期持续约3个月,单花花期为9.6±0.6 d;花蜜较丰富且稀薄,具有较短的花冠管和己糖为主的花蜜糖组成;访花动物主要是中华蜜蜂和多种食蜜鸟类,尤其是短喙的泛化鸟类,且在非自然生境中仍然能吸引鸟类访花;完全自交亲和但需要传粉者才能完成授粉,不存在花粉限制;不同授粉处理种子的发芽能力无显著差异;中华蜜蜂能有效传粉,鸟类的传粉作用需进一步验证。综上所述,火把花可供观赏的时间很长,具有明显的吸引鸟类访花的能力,容易通过有性繁殖途径快速获得大量幼苗。     

Are pollinators the agents of selection on flower colour and size in irises?

Plant–pollinator interactions are believed to play a major role in the evolution of floral traits. Flower colour and flower size are important for attracting pollinators, directly influencing reproduction, and thus expected to be under pollinator‐mediated selection. Pollinator‐mediated selection is also proposed to play a role in maintaining flower colour polymorphism within populations. However, pigment concentrations, and thus flower colour, are also under selective pressures independent of pollinators. We quantified phenotypic pollinator‐mediated selection on flower colour and size in two colour polymorphic Iris species. Using female fitness, we estimated phenotypic selection on flower colour and size, and tested for pollinator‐mediated selection by comparing selection gradients between flowers open to natural pollination and supplementary pollinated flowers. In both species, we found evidence for pollen limitation, which set the base for pollinator‐mediated selection. In the colour dimorphic Iris lutescens, while pigment concentration and flower size were found to be under selection, this was independent of pollinators. For the polymorphic Iris pumila, pigment concentration is under selective pressure by pollinators, but only for one colour morph. Our results suggest that pollinators are not the main agents of selection on floral traits in these irises, as opposed to the accepted paradigm on floral evolution. This study provides an opposing example to the largely‐accepted theory that pollinators are the major agent of selection on floral traits.     

Extremely reduced sexual reproduction in the clonal cactus Echinopsis thelegona

Sexual and asexual reproduction may occur simultaneously in some plant species. Under certain environmental conditions asexual reproduction is predominant, which generates ecological consequences on sexual fecundity. In this context, we studied the reproductive ecology of the creeping clonal cactus Echinopsis thelegona in La Bodega (Salta, Argentina), where low fruit and seed production was preliminarily observed. Specifically, we studied the flower availability, fruit and seed production, reproductive system, floral visitors and effects of neighbor ramets on reproductive success. The number of available flowers per day was low, and fruit production was low or null as well. Echinopsis thelegona is self-incompatible. Although its flowers have sphingophilous traits, we did not find evidence of moths visiting them. Only native and exotic bees visited the flowers of this species, though with a low number of visits. Therefore, nocturnal visitors were not registered as pollinators of E. thelegona, perhaps because of their low local abundances. On the other hand, bees behaved as inefficient pollinators of E. thelegona due to their foraging behavior, which moves pollen within individuals. A pollen-addition experiment revealed that there is no fruit production at short distances among ramets. Therefore, the combination of self-incompatibility, low flower production and low local abundance of pollinators could account for the low fruit production observed in this species. This finding suggests that populations of E. thelegona persist by clonality and that they tend toward the loss of sexuality.