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1.
This study analyses the pollination systems and biogeography of three allopatdc species of Schisandra (Section Euschisandra) consisting of S.glabra (North America),S.bicolor (China),and S.repanda (Japan); the clade is delimited in a phylogenetic tree of Schisandraceae constructed with nuclear and plastid genes.The male and female flowers of these species have similar floral structures,but exhibit different pollination systems.At the base of the clade,S.glabra is pollinated by a wide variety of beetles and flies in a generalist pollination system that also includes floral heat and the use of male and female flowers as brood sites for insects.In Asia,however,S.bicolor and S.repanda are pollinated exclusively by one or two different species of gall midges (Resseliella spp.) in a specialist pollination system.In this system only female,pollen-eating gall midges pollinate the flowers and breed on nearby spiderwebs.The gall midge pollination system is specialized and derived from the generalist system in S.glabra,and basal in the clade.Pollen is the main floral resource,and we hypothesize it is exploited to enrich eggs,and as a result species of gall midges could increase reproductive fitness by feeding on a single dependable food source.Subsequently the life cycles of the plants and insects evolved into a tight association in old stable plant communities in the Sino-Japanese flora.Divergence times for the plant species are presented and correlated with past distributions and migration routes.  相似文献   

2.
The plants of Kadsura longipedunculata (Schisandraceae) are monoecious and possess either red or yellow male flowers (the androecium), with yellow tepals, and yellow female flowers. All flower types simultaneously produce heat and floral odours (dominated by methyl butyrate) throughout a 4–5-h nocturnal period. The flowers are pollinated only by female, pollen-eating Megommata sp. (Cecidomyiidae). Pollen is the only reward, and female flowers use the same attractants as male flowers but offer no food (pollination by deceit). Open pollinated flowers in nature varied in fruit set from 8 to 92%. Megommata (subfamily Cecidomyiinae, supertribe Cecidomyiidi), consists of six described species, which feed on Coccoidea (scale insects) and are distributed worldwide.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 523–536.  相似文献   

3.
Many angiosperm lineages present transitions from bee to hummingbird pollination. The flower design in most of these lineages includes either corolla tubes or nectar spurs, structures that commonly experienced an elongation with the acquisition of hummingbird pollination. It is proposed that this increases the fit between the bird head and flower structures, and isolates or partially blocks bees from the interaction. But can this transition occur if the ancestral flower design lacks tubes or spurs? Here we focus on the transition from bee to hummingbird pollination in the Loasaceae subfamily Loasoideae. Loasoideae flowers have radial corollas with separated petals; therefore, they do not display corolla tubes nor nectar spurs. These flowers also present a whorl of nectar scales and staminodes, unique to the subfamily, which is involved in flower–pollinator fit and in nectar harvesting. To explore flower shape adaptation to hummingbird pollination, we tested for correspondence between pollinators and flower shape in Loasoideae. In order to achieve this, we first compared the evolutionary history of flower phenotype and pollination mode, and then used stochastic character mapping and geometric-morphometric variables in a comparison of alternative evolutionary models. The results of our study suggest that the transition from bee to bird pollination was accompanied by changes in the shape of the staminodial complex, along with the evolution of relatively closed corollas. Moreover, while bird pollination seems to be the end point in the evolution of pollination syndromes in many angiosperm lineages, rodent pollinated flowers probably evolved from ancestral bird pollinated flowers in Loasoideae. Our findings suggest that the evolution of bird pollinated flowers from ancestral bee pollinated flowers does not require the presence of corolla tubes or spurs, and can take place as long as the flower design includes structures participating in flower–pollinator fit.  相似文献   

4.
A previously undescribed pollination system involving a monoecious tree species, Artocarpus integer (Moraceae), pollinator gall midges, and fungi is reported from a mixed dipterocarp forest in Sarawak, Borneo. The fungus Choanephora sp. (Choanephoraceae, Mucorales, Zygomycetes) infects male inflorescences of A. integer, and gall midges (Contarinia spp., Cecidomyiinae, Diptera) feed on the fungal mycelia and oviposit on the inflorescence. Their larvae also feed on the mycelia and pupate in the inflorescence. The gall midges are also attracted by female inflorescences lacking mycelia, probably due to a floral fragrance similar to that of male inflorescences. Because of the sticky pollen, dominance of Contarinia spp. in flower visitors, and pollen load observed on Contarinia spp. collected on both male and female inflorescences, Artocarpus integer is thought to be pollinated by the gall midges. Although several pathogenic fungi have been reported to have interactions with pollinators, this is the first report on a pollination mutualism in which a fungus plays an indispensable role. The pollination system described here suggests that we should be more aware of the roles fungi can play in pollinations.  相似文献   

5.
The widespread pattern of parallel flower evolution as an adaptation for particular pollinator agents, known as "pollination syndromes", has long drawn attention from evolutionary biologists. Here, we report parallel evolution of saucer-shaped flowers and an associated unusual pollination system within the lineage Heucherina, a group of saxifragaceous genera. Field observations reveal that 18 of 28 plant species studied are pollinated almost exclusively by fungus gnats (Mycetophilidae). Among the 18 species with a fungus-gnat pollination system, 13 have characteristic saucer-shaped flowers and are pollinated mainly by several unspecialized mycetophilid genera with short mouthparts. We performed phylogenetic analyses using nucleotide sequences of external and internal transcribed spacers of nuclear ribosomal DNA and reconstructed ancestral floral morphologies with an establishment of the model of floral character evolution under a maximum-likelihood framework. Our analysis indicates that there is significant directionality in the evolutionary shifts of floral forms in the Heucherina. The inferred phylogeny further supports four origins of saucer-shaped flowers, which is shared among 14 species that are traditionally classified into the genus Mitella. In addition, our analysis indicates the extensive polyphyly of genus Mitella, as also suggested previously. The results suggest that the flower-visiting fungus gnats have caused convergent selection for the saucer-shaped flower repeatedly evolved within Heucherina.  相似文献   

6.
Flower form is one of many floral features thought to be shaped by pollinator‐mediated selection. Although the drivers of variation in flower shape have often been examined in microevolutionary studies, relatively few have tested the relationship between shape evolution and shifts in pollination system across clades. In the present study, we use morphometric approaches to quantify shape variation across the Andean clade Iochrominae and estimate the relationship between changes in shape and shifts in pollination system using phylogenetic comparative methods. We infer multiple shifts from an ancestral state of narrow, tubular flowers toward open, bowl‐shaped, or campanulate flowers as well as one reversal to the tubular form. These transitions in flower shape are significantly correlated with changes in pollination system. Specifically, tubular forms tend to be hummingbird‐pollinated and the open forms tend to be insect‐pollinated, a pattern consistent with experimental work as well as classical floral syndromes. Nonetheless, our study provides one of the few empirical demonstrations of the relationship between flower shape and pollination system at a macroevolutionary scale.  相似文献   

7.
In some species pollination may result in rapid changes in perianth colour and form (petal senescence and abscission, flower closure), rendering the flowers less attractive to pollinators. It has been suggested that this effect is mediated by ethylene. Flowers from about 200 species and 50 families were exposed to ethylene (3 ppm for 24 h at 20 degrees C). The effects on petal senescence and abscission have been described previously. Flower closure and perianth colour changes were generally ethylene-sensitive, but responses showed no consistency within families. Several flowers known to respond to pollination by rapid cessation of attractiveness were also exposed to ethylene: this produced the same effect as pollination, both on flower colour and form. Species that respond to pollination by changing flower form or colour were found exclusively in families in which the species are generally ethylene-sensitive (with regard to changes in perianth form and colour). However, several families are generally ethylene-sensitive but contain no species reported to respond to pollination.  相似文献   

8.
Strong evidence exists that fragmentation negatively affects pollination and plant reproduction, but little research has been conducted with regards to tropical trees. Specifically, effects of forest fragmentation on reproduction of plants with beetle‐pollinated flowers are poorly understood, and there are no data on the impact of fragmentation on reproduction in the structurally important tropical family Annonaceae. We examined the relationship between fragment size, pollinator abundance and seed set of beetle‐pollinated Anaxagorea dolichocarpa (Annonaceae) in a disturbed Brazilian Atlantic rainforest. Flower and fruit production and abundance of pollinators were quantified over ten months in three large (306–388 ha) and three small (6–14 ha) forest fragments. We recorded per flower pollinator abundance, resulting fruit set (fruits per flower) and seed set (monocarps per fruit) for a total of 209 individually marked flowers, and compared pollinator abundance in 186 flowers across all fragments. Flower and fruit production differed among fragments, but were similar for the combined large and small fragments. Between 64.8% (large fragments) and 66.3% (small fragments) of flowers received at least one pollinator. We found no significant difference in pollinator numbers between large and small fragments, and no correlation between pollinator abundance and fruit and seed set. A single visitor had a high probability of pollinating a flower. We conclude that 1) fragment size had no influence on pollinator number and plant reproductive success, and 2) generalist behavior of the pollinating beetles mitigate the risk of pollination failure for the reproductively specialized plant. However, further research may yet reveal genetic impoverishment of populations in small fragments due to restricted pollinator movements.  相似文献   

9.
Summary Under conditions where resources are limited, there are often negative correlations between components of maternal yield, or between fruit and flower production. Pollination, in turn, may vary among individuals and influence total maternal expenditure. We examined the impact of variation in pollination thoroughness upon yield components and overall plant growth in wild radish (R. raphanistrum) plants grown in the greenhouse. Plants received different pollination treatments in which 0% to 100% of all flowers produced were hand-pollinated. Fruit set was increased by hand-pollination, but rarely exceeded 30%, even when more than 50% of the flowers were pollinated. Plants receiving more thorough pollination or having greater proportion fruit set produced significantly smaller seeds. Seed number per fruit was not influenced by pollination treatment. Mean values of yield components and interactions between components often varied among plants from different maternal families. Increasing pollination thoroughness also resulted in dramatic decreases in flower production. If male fitness is related to flower number, there may be a tradeoff between maternal fecundity and successful pollen export operating at the whole-plant level in this species.  相似文献   

10.
Recent studies on the obligate interaction between fig trees and their pollinating agaonid wasps have focused on population aspects and wasp?Cseed exploitation at the level of the inflorescence. Detailed studies on larval and gall development are required to more fully understand how resources are exploited and adaptations fine-tuned by each partner in nursery pollination mutualisms. We studied the larval development of the active pollinating fig wasp, Pegoscapus sp., and the galling process of individual flowers within the figs of its monoecious host, Ficus citrifolia, in Brazil. The pollinator development is strongly dependent on flower pollination. Figs entered by pollen-free wasps were in general more likely to abort. Retained, unpollinated figs had both higher larval mortality and a lower number of wasps. Pegoscapus sp. larvae are adapted to plant development, with two contrasting larval feeding strategies proceeding alongside gall development. The first two larval stages behave as ovary parasites. Later larval stages feed on hypertrophied endosperm. This indicates that a successful galling process relies on endosperm, and also reveals why pollination would be a prerequisite for the production of high-quality galls for this Pegoscapus species.  相似文献   

11.
Yuan LC  Luo YB  Thien LB  Fan JH  Xu HL  Chen ZD 《Annals of botany》2007,99(3):451-460
BACKGROUND AND AIMS: The mutualistic interaction between insects and flowers is considered to be a major factor in the early evolution of flowering plants. The Schisandraceae were, until now, the only family in the ANITA group lacking information on pollination biology in natural ecosystems. Thus, the objective of this research was to document the pollination biology and breeding system of Schisandra henryi. METHODS: Field observations were conducted in three populations of S. henryi and the floral phenology, floral characters and insect activities were recorded. Floral fragrances were sampled in the field and analysed using TCT-GC-MS. Floral thermogenesis was measured with a TR-71U Thermo Recorder. Pollen loads and location of pollen grains on insect bodies (including the gut) were checked with a scanning electron microscope and under a light microscope. KEY RESULTS: Schisandra henryi is strictly dioecious. Male flowers are similar to female flowers in colour, shape, and size, but more abundant than female flowers. The distance between tepals and the androecium or gynoecium is narrow. Neither male nor female flowers are fragrant or thermogenic. Schisandra henryi is pollinated only by adult female Megommata sp. (Cecidomyiidae, Diptera) that eat the pollen grains as extra nutrition for ovary maturation and ovipositing. Both male and female flowers attract the pollinators using similar visual cues and thus the female flowers use deceit as they offer no food. CONCLUSIONS: Schisandra henryi exhibits a specialized pollination system, which differs from the generalized pollination system documented in other ANITA members. Pollen is the sole food resource for Megommata sp. and the female flowers of S. henryi attract pollinators by deceit. This is the first report of predacious gall midges utilizing pollen grains as a food source. The lack of floral thermogenesis and floral odours further enforces the visual cues by reducing attractants for other potential pollinators.  相似文献   

12.
Genetic engineering of parthenocarpic fruit development in tomato   总被引:9,自引:0,他引:9  
Parthenocarpy was engineered in two genotypes of Lycopersicon esculentum Mill. by using the DefH9-iaaM chimeric gene. The parthenocarpic trait consists of fruit set and growth in the absence of fertilization. Seedless parthenocarpic fruits were obtained from emasculated flowers, and fruits with seeds from pollinated flowers. All parthenocarpic tomato plants analysed expressed the DefH9-iaaM gene during flower development. The fruit set percentage of emasculated transgenic flowers was similar to that of control plants. In 7 out of 8 independent transgenic plants, the fresh weight of fruits derived from pollinated or emasculated flowers did not significantly differ from that of fruits obtained by pollination of the control plants. The pH of the parthenocarpic fruit was generally unaffected and the soluble solid concentration was either unchanged or increased. Thus, the DefH9-iaaM gene is a genetic tool that might be used to improve tomato productivity.  相似文献   

13.
Allison A. Snow 《Oecologia》1982,55(2):231-237
Summary Initial seed set and fruit set were pollen-limited in a Costa Rican population of Passiflora vitifolia, a self-incompatible species with 200–350 ovules per flower. Pollination intensity was measured by counting the number of allogamous pollen grains on stigmas of the large one-day flowers. Hand-pollinations demonstrated that 25–50 pollen grains are required for fruit set, and >450 are needed for maximum seed set, with a pollen:seed ratio of about 1.6:1.0. Hummingbirds (Phaethornis superciliosus) delivered sufficient allogamous pollen for maximum seed set to only 28% of the flowers examined. Naturally pollinated flowers yielded fewer fruits and fewer seeds per fruit than those pollinated by hand. Most pollen transferred by humming-birds was self-incompatible; emasculated flowers yielded higher seed set than flowers with intact anthers. Visitation rates did not provide a good index of effective pollination.There were significant differences in ovule number, maximum seed set, and maximum per cent seed set among individual vines. More than half of an individual's flowers failed to set fruit, whether pollinated by birds or by hand. In this population, maximum reproductive potential may be limited by maternal resources for fruit development, but seed set varies with pollination intensity. Pollen-limited seed set may be a disadvantage of self-incompatibility, especially in species with many-seeded fruits.  相似文献   

14.
Abstract: We studied the reproductive success and pollinators of Cucurbita maxima ssp. andreana in different disturbed habitats where it grows naturally. Data were obtained from three populations. One grew within a soybean crop, the other within a corn crop, and the third in an abandoned crop field. Cucurbita maxima ssp. andreana is an annual vine with a flowering period from December to April. Male flowers appear first, thereafter female and male flowers appear together. Flower lifetime (9 h) was similar in male and female flowers. The pollinator guild was comparable for the three populations but some differences in the frequency of the insect species were observed. Native bees were the main pollinators in the population in the abandoned field, while beetles pollinated the populations in crop fields. These differences were not linked with the pre-emergent reproductive success, fruit and seed set, or fruit quality. This is a self-compatible plant. Fruit and seed set and fruit traits (total mass, width and length of fruits, number of seeds per fruit, and seed mass) did not show significant differences between hand-cross and hand-self pollinated flowers. This wild cucurbit is a generalist with respect to pollinator guild, and flower visitors seem to be highly efficient in pollen transference. Cucurbita maxima ssp. andreana is well adapted to disturbed habitats because plants ripened fruits successfully, regardless of the group of insects visiting flowers.  相似文献   

15.
Nectaries and reproductive biology of Croton sarcopetalus (Euphorbiaceae)   总被引:1,自引:0,他引:1  
Flower morphology, nectary structure, nectar chemical composition, breeding system, floral visitors and pollination were analysed in Croton sarcopetalus , a diclinous-monoecious shrub from Argentina. Male flowers have five receptacular nectaries, with no special vascular bundles, that consist of a uniserial epidermis with stomata subtended by a secretory parenchyma. Female flowers bear two different types of nectaries: inner (IN) and outer (ON) floral nectaries. IN, five in all, are structurally similar to the nectaries of male flowers. The five ON are vascularized, stalked, and composed of secretory, column-shaped epidermal cells without stomata subtended by secretory and ground parenchyma. In addition, ON act as post-floral nectaries secreting nectar during fruit ripening. Extrafloral nectaries (EFN) are located on petioles, stipules and leaf margins. Petiolar EFN are patelliform, stalked and anatomically similar to the ON of the female flower. Nectar sampled from all nectary types is hexose dominant, except for the ON of the female flower at the post-floral stage that is sucrose dominant. The species is self-compatible, but geitonogamous fertilization is rarely possible because male and female flowers are not usually open at the same time in the same individual, i.e. there is temporal dioecism. Flowers are visited by 22 insect species, wasps being the most important group of pollinators. No significant differences were found in fruit and seed set between natural and hand pollinated flowers. This pattern indicates that fruit production in this species is not pollen/pollinator limited and is mediated by a wide array of pollinators.  相似文献   

16.
濒危植物独花兰的传粉生物学初步观察   总被引:9,自引:0,他引:9  
独花兰(Changnienia amoena Chien)为我国特有的单种属植物,近年因生境破碎化和过度采挖,其野生资源日渐减少。迄今对独花兰极为有限的研究表明,其结实率很低或根本不结实,其传粉媒介也一直未被发现。2002年3~4月,我们对神农架2个移植居群和5个天然居群进行了传粉生物学的定点观察,发现雌性三条熊蜂(Bombus (Diversobombus)trifasciatus Smith)、仿熊蜂(Bombus (Tricornibombus) imitator Pittion)和蜜蜂均访问独花兰,但只有二条熊蜂身体粘有花粉块,是独花兰的有效传粉者。三条熊蜂的访问频率很低,在113h的观察中只有9次访问,但在一个天然居群(population 3)中曾观察到一天4次的最高访问频率;访问主要在12:00~15:00出现,但在花上停留时间很短,不超过10s。在末被授粉的情况下,独花兰花朵大约3周后自然枯萎,但受粉后3、4d内即出现~系列形态和颜色的变化,包括花梗逐渐伸长,子房在花梗逐渐停止伸长后开始膨大等,表明花梗伸长可作为结实(授粉成功)的指标。人工授粉实验表明,自花、异花受粉后花梗均伸长,而套袋隔离花的则花梗不伸长,说明独花兰是自交亲和的异交种,需要昆虫传粉。根据传粉者的访问频率、居群中果实的分布,尤其是花距内无花蜜等特征,我们认为独花兰是一种欺骗性传粉的兰花。相对于其他欺骗性传粉的兰花,独花兰的自然结实率并不很低(26.98%),这与居群规模小会提高欺骗性传粉兰花结实率这一观点吻合。花粉块的输出数远高于结实数,这说明独花兰存在一定的花粉浪费。  相似文献   

17.
Abstract Most deceit‐pollinated species involve floral dimorphisms characterized by the presence of rewarding male flowers and nonrewarding female flowers. It has been proposed that this polymorphism establishes the conditions for the action of frequency dependent selection (FDS). The tendency of foraging animals to aggregate in areas of high resource density suggests that pollination efficiency and fruit production may be positively influenced by flower density (density dependent selection, DDS). In this paper we offer a graphical model describing the effects of FDS and DDS on a monoecious species pollinated by deceit. We test the FDS and DDS assumptions and the predictions of the model using field observations and experimental populations of Begonia gracilis in which population sex ratio and flower density were controlled. We found a marked effect of both FDS and DDS on pollinator visitation, fruit‐set, and on the probability of female flowers to setting fruits. We conclude that these two types of selection have had a strong influence on the evolution of deceit‐pollinated species.  相似文献   

18.
Concerted changes in flower morphology and pollinators provide strong evidence on adaptive evolution. Schizanthus (Solanaceae) has zygomorphic flowers and consists of 12 species of annual or biennial herbs that are distributed mainly in Chile and characterized by bee-, hummingbird-, and moth-pollination syndromes. To infer whether flowers diversified in relation to pollinator shifts, we traced the evolutionary trajectory of flower traits and visitors onto a phylogeny based on sequence data from ITS, waxy, and trnF/ndhJ DNA. Maximum-likelihood ancestral reconstruction of floral traits suggests that ancestral Schizanthus had a bee-pollination syndrome. The hummingbird syndrome evolved in S. grahamii, a high elevation species in the Andes. The moth syndrome evolved in the ancestor of three species that inhabit the Atacama Desert. Results of mapping flower visitors onto the phylogeny show that the shift from bee to hummingbird pollination concurred with a shift in pollinators as predicted by the syndromes. However, the same pattern was not found for the moth syndrome. Visits by moths were observed only in one of the three moth-syndrome species, and at a very low rate. This mismatch suggests either anachronic floral characters or maintenance of rare, imperceptible moth pollination backed up by capacity for autonomous selfing. Overall, results suggest that diversification of flower traits in Schizanthus has occurred in relation to pollinator shifts.  相似文献   

19.
Wild and managed pollinators are the key component of biodiversity, contributing to important ecosystem services such as pollination and supporting human food security. Pollination by insects is a crucial component of the food chain that ensures the production of fruits and strongly affects the fruit quality, but the effect of insect pollination on fruit physiological and chemical parameters is largely unknown. The current study was conducted to determine the insect pollinators diversity and their relative abundance in the loquat (Eriobotrya japonica) orchard during 2017–2019. Further, the effect of insect pollinators pollination on the physiological and chemical parameters of fruit quality as compared to control pollinated flowers was investigated. The results revealed that a total of 22 species from 3 families (Apidae, Halictidae, and Syrphidae) were identified during the flowering season. The Apidae and Syrphidae were the most frequently observed families with major groups honey bees (67.89%) and hoverflies (21.57%), respectively. Moreover, results indicated that the fruit yield by the open-pollinated flowers (22.31 ± 0.34 kg/tree) was significantly higher than the control pollinated flowers (14.80 ± 0.25 kg/tree). Physiological and chemical parameters of loquat fruit differed significantly when fruits obtained from open-pollinated flowers as compared to control pollinated flowers. These results suggested that native insect pollinators play important role in the fruit quality of loquat. Hence, maintenance of appropriate habitat of native pollinators near loquat orchards is necessary to ensure good productivity and fruit quality.  相似文献   

20.
Dioecy allows separation of female and male functions and therefore facilitates separate co‐evolutionary pathways with pollinators and seed dispersers. In monoecious figs, pollinators' offspring develop inside the syconium by consuming some of the seeds. Flower‐stage syconia must attract pollinators, then ripen and attract seed dispersers. In dioecious figs, male (“gall”) figs produce pollen but not viable seeds, as the pollinators' larvae eat all seeds, while female (“seed”) figs produce mostly viable seeds, as pollinators cannot oviposit in the ovules. Hence, gall and seed figs are under selection to attract pollinators, but only seed figs must attract seed dispersers. We test the hypothesis that seed and gall syconia at the flower stage will be similar, while at the fruiting stage they will differ. Likewise, monoecious syconia will be more similar to seed than gall figs because they must attract both pollinators and seed dispersers. We quantified syconium characteristics for 24 dioecious and 11 monoecious fig species and recorded frugivore visits. We show that seed and gall syconia are similar at the flower stage but differ at the fruit stage; monoecious syconia are more similar to seed syconia than they are to gall syconia; seed and gall syconia differentiate through their ontogeny from flower to fruit stages; and frugivores visit more monoecious and seed syconia than gall syconia. We suggest that similarity at the flower stage likely enhances pollination in both seed and gall figs and that differentiation after pollination likely enhances attractiveness to seed dispersers of syconia containing viable seeds. These ontogenetic differences between monoecious and dioecious species provide evidence of divergent responses to selection by pollinators and seed dispersers.  相似文献   

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