The Role of Flower Inclination, Depth, and Height in the Preferences of a Pollinating Beetle (Coleoptera: Glaphyridae)

Amphicoma (Glaphyridae) beetles are important pollinators of red bowl-shaped flowers in the Mediterranean. The role of color and shape in flower choice is well studied but the roles of inclination, depth, and height have seldom been investigated. Under field conditions, models were used to experimentally manipulate these three characters and visitation rates of beetles were recorded. Models with red horizontal surfaces were visited significantly more often than models with red vertical surfaces. Shallow flower models were visited significantly more than deeper equivalents. Models below or at the height of natural flower populations elicited significantly more landings than models above the height of flowers. Inclination, depth, and height characteristics are all likely to be important components in the flower preferences exhibited by pollinating beetles.     

基于花青素代谢培育蓝色花卉的研究进展

花色是植物吸引昆虫传播花粉的主要因素,对于植物在自然界的生存必不可少,也是观赏植物最重要的性状之一。在蓬勃发展的花卉产业中,色彩各异花卉的培育,可以弥补自然花色的匮乏,但是令人垂涎的蓝色花比较难培育。花色的多样性主要是由花青素及其衍生物的种类和含量等因素决定的,飞燕草色素的合成是形成蓝色花的关键因素,许多植物体内缺少合成飞燕草色素的结构基因。近年来,利用基因工程技术培育蓝色花的研究也时有报道。文中以常见的观赏植物为例,基于花青素代谢调控,从影响飞燕草色素合成的关键因素和不同分子改良途径培育蓝色花等几个方面对植物花朵呈色的机制进行了综述,并展示不同分子育种策略可能在其他领域的应用,为其他植物或经济作物的色泽改良如彩色棉蓝色纤维的培育等提供参考和技术支持。     

Genetic control of white flower color in scarlet rosemallow (Hibiscus coccineus Walter)

Scarlet rosemallow (Hibiscus coccineus Walter) is a diploid, perennial, erect, and woody shrub. The species is a desirable inclusion in home landscapes because it is a native plant with attractive flowers and unusual foliage. The objective of these experiments was to determine the number of loci, number of alleles, and gene action controlling flower color (red vs. white) in scarlet rosemallow. Three white-flowered and 1 red-flowered parental lines were used to create S(1) and F(1) populations, which were self-pollinated or backcrossed to generate S(2), F(2), and BC(1) populations. Evaluation of these generations showed that flower color in these populations was controlled by a single diallelic locus with red flower color completely dominant to white. I propose that this locus be named "white flower" with alleles W and w.     

Nonrandom Composition of Flower Colors in a Plant Community: Mutually Different Co-Flowering Natives and Disturbance by Aliens

When pollinators use flower color to locate food sources, a distinct color can serve as a reproductive barrier against co-flowering species. This anti-interference function of flower color may result in a community assembly of plant species displaying mutually different flower colors. However, such color dispersion is not ubiquitous, suggesting a variable selection across communities and existence of some opposing factors. We conducted a 30-week study in a plant community and measured the floral reflectances of 244 species. The reflectances were evaluated in insect color spaces (bees, swallowtails, and flies), and the dispersion was compared with random expectations. We found that co-existing colors were overdispersed for each analyzed pollinator type, and this overdispersion was statistically significant for bees. Furthermore, we showed that exclusion of 32 aliens from the analysis significantly increased the color dispersion of native flowers in every color space. This result indicated that aliens disturbed a native plant–pollinator network via similarly colored flowers. Our results demonstrate the masking effects of aliens in the detection of color dispersion of native flowers and that variations in pollinator vision yield different outcomes. Our results also support the hypothesis that co-flowering species are one of the drivers of color diversification and affect the community assembly.     

Floral color change and the attraction of insect pollinators in lungwort (Pulmonaria collina)

We studied the effect of floral color change on long- and short-distance attraction of insect pollinators to the herb lungwort, Pulmonaria collina. Lungwort flowers change color with age from red to blue. Young red flowers had a significantly greater pollen and nectar reward and were significantly more often unpollinated than old blue ones. Red and blue flowers both influenced long-distance attractiveness of plants, defined as the number of insect approaches towards an individual plant. After reaching a plant, flower visitors preferred to visit young red flowers. Therefore, short-distance attractiveness, defined as the number of flowers visited successively on an individual plant, was influenced mainly by the number of young red flowers. The co-occurrence of the change in reproductive ability, in amount of reward, and in flower color enabled lungwort plants to direct pollinators to reproductive, highly rewarding red flowers. The data suggest that by maintaining changed flowers lungwort plants can increase their long-distance attraction and simultaneously enhance the probability of flower visits to pre-changed flowers. Thus, we propose floral color change as a mechanism that can increase the efficiency of pollen transfer to enhance plant fitness. Received: 2 November 1998 / Accepted: 14 July 1999     

Flower color microevolution in wild radish: evolutionary response to pollinator-mediated selection

Evolutionary ecologists are fundamentally interested in how species interactions affect evolutionary change. We tested the degree to which plant-pollinator interactions affect the frequency of flower color morphs of Raphanus sativus. Petal color in R. sativus is determined by two independently assorting loci, producing four petal colors (yellow, white, pink, and bronze). We assessed the impact of pollinator discrimination on changes in flower color variation by comparing the frequency of colors produced in the presence (open pollination) versus absence (null pollination) of pollinator discrimination. We also assessed the impact of postpollination and developmental effects on progeny colors using equal pollinations with all four color morphs. Our results from open pollinations found an overrepresentation of yellow progeny in the next generation, when compared with both null pollinations and cumulative ratios based on Hardy-Weinberg and linkage equilibria assumptions. When these results were combined with those from equal pollinations, the overrepresentation of yellow could be attributed to selection from pollinators. Yet, surveys in the field the following year found no flower color frequency changes in the next generation. These results illustrate that flower color microevolution can be driven by both pollinator discrimination and other nonpollinator selective forces acting during the seed-to-adult transition, countering selection imposed by pollinators.     

Floral color change in Weigela middendorffiana (Caprifoliaceae): reduction of geitonogamous pollination by bumble bees

We examined the significance of retaining color-changed flowers in pollination success of Weigela middendorffiana through a single visit of bumble bees. Inner parts of flowers changed color with age from yellow to red. In an investigation of the mating system, duration of each color phase, reproductive ability of each of the color-phase flowers, and the effects of color-changed flowers on bumble bee behavior (1) flowers of this species were self-incompatible, (2) color-changed flowers provided little reward to pollinators and little residual reproductive ability, (3) the timing of floral color change was delayed with the progress of flowering season within individual plants, while the duration of the red phase shortened with the progress of flowering season, and (4) red-phase flowers did not attract bumble bees at a distance but did contribute to reducing the number of successive flower visits during a single stay within the plants. Red-phase flowers seemed to indicate the low reward level of old flowers and functioned as a cue to discourage pollinators from staying longer on the same plant. Our results predict that the retention of color-changed flowers without sexual function can enhance the pollination success of a whole plant through male function by reducing successive flower visits during a single stay of pollinators, i.e., geitonogamous pollination.     

Floral color changes in Boswellia sacra Flueck. (Burseraceae): A dialogue between plant and pollinator

The present study provides new information about the reproductive biology of Boswellia sacra (Burseraceae), focusing on the nectary and its attractiveness for pollinators. The nectary disc changes its color from yellow to orange and red during the flower development. The colors are related to the main period of the stigmatic receptivity, to the dehiscence of anthers with pollen presentation and the nectar secretion. Pollinators preferentially visit the flowers in the “yellow” phase and neglect the “red phase”. This suggests a sophisticated dialogue between the plant and its pollinators. The color change from yellow to red occurs in a very short time (less than 24 h) and it is due to the accumulation of anthocyanins. Despite this dialogue between plant and pollinators, the number of fruits is often scanty.     

Bumblebees Do Not Respond to Variance in Nectar Concentration

Worker bumblebees (Bombus fervidus) were given repeated binary choices between two colors of artificial flowers with the same associated mean nectar concentration (X? = 20%), but with different variances in nectar concentration. Flowers of one color, yellow or blue, rewarded a bee with 1 μl of 20% sucrose solution (low-variance flower type) on each visit (p = 1) and flowers of the other color rewarded a bee on each visit with 1 μl of either 10% or 30% sucrose (p = 0.5; high-variance flower type). Of the 10 bees tested, nine showed no preference for either the high- or low-variance flowers (indifferent or risk-insensitive). This result is similar to honeybee responses to variation in nectar concentration, despite differences in foraging ecology between bumblebees and honeybees. Flower-choice behaviour in the presence of variance in nectar concentration is a response to the expected concentration of the alternative flower types. Possible mechanisms of risk-sensitive foraging behaviour in bees are discussed.     

Pollination biology of Cymbidium goeringii (Orchidaceae) in China

The genus Cymbidium comprises three subgenera with ca. 50 species. Interactions between pollinators and plants have been studied in the two subgenera Cymbidium and Cyperorchis, but only a few studies in the subgenus Jensoa have been reported. Here we report on the reproductive characteristics of C. goeringii (in sub-genus Jensoa) in three populations in the southwest of Hunan Province, China, during the winter from December 2005 to March 2006. Floral phenological and morphological features, behavior of visitors, the breeding system, and fruit sets under natural conditions were studied. The flowers of C. goeringii were strongly fragrant, but did not present any rewards to the visitors. The flowering period of C. goeringii in the studied populations lasted about 40 days, and most flowers (about 60%) opened within 30 days. Flowers opened immediately when temperature increased obviously and reached to about 16 ℃. The flowering time of the pollinated flowers, unpollinated flow-ers and the flowers with pollinarium removed were similar. Two bees of Apidae, Apis cerana cerana (honeybee) and Anthophora melanognatha, were observed visiting flowers of C. goeringii, but only the honeybees performed as pollinators. The honeybees mostly visited the orchid flowers at 10:00–17:00 on sunny days with temperature above 10 ℃. A total of only thirteen visits were observed during 20 days of observation, indicating pollinators were rare. Honeybees directly landed on the upper surface of the labellum and inserted their heads into the flowers between column and labellum, while the hind legs trod on the surface of the curved downward mid-lobe of label-lum. When a honeybee landed on the labellum of a flower, the labellum moved up and down slightly. After the honeybee entered the flower further, its head might touch the foot of the column. At this time, the body of the honeybee was parallel with the upper surface of the labellum. Then the honeybee used its front legs to scratch on the callus ridges on the upper surface of the labellum, and its hind legs hooked the edges of the side lobe of label-lum, trying to exit forcibly from the flower. During exiting process, sometimes the honeybee’s body was arched owing to tension. In this case, the surface of the scutellum came into close contact with the viscidium and then pollinaria, together with the anther cap, were removed. When this honeybee visited next flower, the pollinaria would be adhered to the stigma when it arched its body during the exiting process. Three plant species flowered synchronously with C. goeringii in the studied areas, but their flowers were different with C. goeringii in color or shape. Because C. goeringii is rewardless to pollinators, the flowers probably attract visitors by olfactory stimu-lus. Breeding system experiments showed no spontaneous autogamy and pollination success relying on pollinators in C. goeringii. Artificial pollination resulted in 90% fruit set by induced autogamy, 100% by pollinating within clone, and 100% by xenogamous pollination, respectively. These results indicate that C. goeringii is highly self-compatible and the fruit production is pollen limited. Because pollinators are essential for fruit set of C. goeringii in natural habitats, protection of wild honeybee populations or apiculture is likely a simple but effective strategy to maintain the orchid populations.     

Intersexual mimicry and flowering phenology facilitate pollination in a dioecious habitat specialist species, <Emphasis Type="Italic">Myristica fatua</Emphasis> (Myristicaceae)

Myristica fatua is a dioecious specialist species restricted to the endangered, freshwater Myristica swamp forests in the Western Ghats, India. Earlier studies have alluded to pollination by deception in members of the Myristica genus, and thus we examined the pollination ecology comprising floral biology, flower production, flower visitors, and reproductive success in M. fatua and inferred the potential strategies that could permit such deception in this habitat specialist tree. Male flowers provide pollen rewards for an extended period of time while female flowers are rewardless and both sexes are visited by generalist insects, mainly by honeybees and stingless bees. Bee visits were significantly more frequent and longer on male than on female flowers as bees collected pollen from male flowers. We found that flower production patterns create a preponderance of males compared to females in the swamp populations. Using a model of honeybee color vision, we found the distance between the color loci of male and female flowers and based on minimum visual angle subtended by these flowers, we suggest that the two floral sexes cannot be discriminated by bees. Bees are likely deceived by the perceptual similarity of rewardless female flowers to pollen-offering male flowers and pollination is the consequence of foraging errors made by pollinators that encounter largely male–rarely female flower mosaics as they forage among clump-distributed M. fatua trees in the swamp habitat.     

COMPETITION FOR HUMMINGBIRD POLLINATION SHAPES FLOWER COLOR VARIATION IN ANDEAN SOLANACEAE

One classic explanation for the remarkable diversity of flower colors across angiosperms involves evolutionary shifts among different types of pollinators with different color preferences. However, the pollinator shift model fails to account for the many examples of color variation within clades that share the same pollination system. An alternate explanation is the competition model, which suggests that color divergence evolves in response to interspecific competition for pollinators, as a means to decrease interspecific pollinator movements. This model predicts color overdispersion within communities relative to null assemblages. Here, we combine morphometric analyses, field surveys, and models of pollinator vision with a species‐level phylogeny to test the competition model in the primarily hummingbird‐pollinated clade Iochrominae (Solanaceae). Results show that flower color as perceived by pollinators is significantly overdispersed within sites. This pattern is not simply due to phylogenetic history: phylogenetic community structure does not deviate from random expectations, and flower color lacks phylogenetic signal. Moreover, taxa that occur in sympatry occupy a significantly larger volume of color space than those in allopatry, supporting the hypothesis that competition in sympatry drove the evolution of novel colors. We suggest that competition among close relatives may commonly underlie floral divergence, especially in species‐rich habitats where congeners frequently co‐occur.     

Are pollinators and seed predators selective agents on flower color in <Emphasis Type="Italic">Gentiana lutea</Emphasis>?

Animals which interact with plants often cause selective pressures on plant traits. Flower color variation within a species might be shaped by the action of animals feeding on the plant species. Pollinators might exert natural selection on color if flower color is related to their foraging efficiency. For example, some pollinator species might require more time to detect particular colors. If that is the case, flower color might have evolved as a pollination exploitation barrier—ensuring that flowers are more visited by the most efficient pollinators. In addition, non-pollinator agents such as predispersal seed predators may select on flower color, if color indicates food resources (seeds) or if color is related to deterrent compounds. We address selection on flower color in a population of Gentiana lutea where color varies among individuals from yellow to orange. We hypothesize that opposed selection from mutualists (pollinators) and antagonists (predispersal seed predators) maintains flower color variation in this population. By means of path analysis we addressed the role of both interactors in flower color selection. We found that selection acts on flower color, mediated by both pollinators and seed predators. Both agents favored yellow-flowered individuals, thus selection by pollinators and seed predators does not maintain flower color variation in this population.     

The Flavonoid Pathway Regulates the Petal Colors of Cotton Flower

Although biochemists and geneticists have studied the cotton flower for more than one century, little is known about the molecular mechanisms underlying the dramatic color change that occurs during its short developmental life following blooming. Through the analysis of world cotton germplasms, we found that all of the flowers underwent color changes post-anthesis, but there is a diverse array of petal colors among cotton species, with cream, yellow and red colors dominating the color scheme. Genetic and biochemical analyses indicated that both the original cream and red colors and the color changes post-anthesis were related to flavonoid content. The anthocyanin content and the expression of biosynthesis genes were both increased from blooming to one day post-anthesis (DPA) when the flower was withering and undergoing abscission. Our results indicated that the color changes and flavonoid biosynthesis of cotton flowers were precisely controlled and genetically regulated. In addition, flavonol synthase (FLS) genes involved in flavonol biosynthesis showed specific expression at 11 am when the flowers were fully opened. The anthocyanidin reductase (ANR) genes, which are responsible for proanthocyanidins biosynthesis, showed the highest expression at 6 pm on 0 DPA, when the flowers were withered. Light showed primary, moderate and little effects on flavonol, anthocyanin and proanthocyanidin biosynthesis, respectively. Flavonol biosynthesis was in response to light exposure, while anthocyanin biosynthesis was involved in flower color changes. Further expression analysis of flavonoid genes in flowers of wild type and a flavanone 3-hydroxylase (F3H) silenced line showed that the development of cotton flower color was controlled by a complex interaction between genes and light. These results present novel information regarding flavonoids metabolism and flower development.     

THE EVOLUTION OF FLORAL COLOR CHANGE: POLLINATOR ATTRACTION VERSUS PHYSIOLOGICAL CONSTRAINTS IN FUCHSIA EXCORTICATA

Field experiments showed that the green-to-red color change in the flowers of Fuchsia excorticata is age-dependent, rather than pollination-induced. Nectar is produced only in green and, to a lesser extent, intermediate-phase flowers; red flowers are postreproductive and are avoided by pollinators (bellbirds). Additional experiments suggested that the red flowers are retained because pollen tubes require at least three days to reach the ovaries, and abscission of the floral tube and accompanying style requires at least another 1.5 days. The change in color directs pollinators away from the postreproductive flowers while these physiological processes are occurring, thereby increasing foraging efficiency and visitation to flowers that are still capable of receiving and donating pollen. No evidence was found to suggest that red-phase flowers function to attract pollinators. Finally, we suggest that the color change evolved through neotenous retention of the green coloration of buds and is a derived trait reflecting an interaction between natural selection and physiological constraints.     

Genetic engineering of flavonoid pigments to modify flower color in floricultural plants

Recent advances in genetic transformation techniques enable the production of desirable and novel flower colors in some important floricultural plants. Genetic engineering of novel flower colors is now a practical technology as typified by commercialization of a transgenic blue rose and blue carnation. Many researchers exploit knowledge of flavonoid biosynthesis effectively to obtain unique flower colors. So far, the main pigments targeted for flower color modification are anthocyanins that contribute to a variety of colors such as red, pink and blue, but recent studies have also utilized colorless or faint-colored compounds. For example, chalcones and aurones have been successfully engineered to produce yellow flowers, and flavones and flavonols used to change flower color hues. In this review, we summarize examples of successful flower color modification in floricultural plants focusing on recent advances in techniques.     

欧报春（Primula vulgaris）不同花色与色素关系及花色遗传初步分析

为了掌握欧报春各花色遗传规律服务于良种生产,通过对欧报春各色花进行色素吸收光谱和薄层层析分析,进行不同花色杂交研究,分析了欧报春各色花所含色素类型及各花色遗传规律。结果显示欧报春群体含多种花色素,单株也可含有多种花色素,形成多变的粉色、红色及蓝色花。黄色深浅主要由类胡萝卜素含量决定。白色对粉色及黄色为隐性遗传,黄色、粉色为显性遗传并有数量遗传特征,黄色与粉色独立遗传。蓝色为多基因控制的隐性遗传,并具有数量遗传特征。     

A molecular phylogeny of Glaphyridae (Coleoptera: Scarabaeoidea): evolution of pollination and association with ‘Poppy guild’ flowers

Among Scarabaeoidea, pollen feeding occurs in two major lineages, pleurostict Scarabaeidae and Glaphyridae. Here we infer for the first time the phylogeny of the scarabaeoid lineage Glaphyridae (Coleoptera) based on molecular data using partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 41 species. Based on the resulting tree topology, we inferred the timing of the origin of pollination and of their coevolution with different flower host taxa, with particular focus on the prominent red-coloured ‘poppy guild’ flowers. All genera of Glaphyridae that were sampled with multiple species were recovered as monophyletic. According to this analysis, the origin of Glaphyridae was around 140 Ma, while crown group divergence was dated to have occurred c. 112 Ma. Pollen feeding originated in Glaphyridae only once and much later than in other important pollinator groups, between 97 and 67 Ma. According to the reconstruction of ancestral feeding traits, Asteraceae (Cicharioidae) were the first hosts of Glaphyridae. Presumably, a further adaptive radiation was triggered by feeding on and pollination of red flowers (poppy guild) which arose at a later stage. It occurred for the first time between 30 and 40 Ma, whereby the clades that use red Ranunculaceae (Pygopleurus spp.) are older than clades using exclusively red Papaveraceae (Eulasia spp.) (25–30 Ma). The rather young age of red Ranunculaceae would imply that Pygopleurus species only subsequently used red Ranunculus species as flower hosts, and that a broad parallel host shift probably from red Papaver spp. to red Ranunculus asiaticus has occurred rather recently.     

花色改造基因工程

自1987年世界首例成功运用转基因技术改造矮牵牛花色以来,花色改造基因工程技术不断展现它在培育新花色品系上的无穷魅力。介绍了近年来运用基因工程技术成功改造花色的3种主要策略:(1)采用反义RNA及共抑制的方法来改变花颜色的深浅;(2)通过导入新基因产生新奇花色;(3)利用转座子构建特殊表达载体,随机激活花色合成的基因来产生嵌合花色。此外,还对转基因株花色不稳定原因进行了讨论。