Hybrid carrot seed crop pollination by the fly Calliphora vicina (Diptera: Calliphoridae)

Many insect species can contribute to crop pollination; however, most growers remain highly dependent on the managed honey bee (Apis mellifera L.) for this service. The European Blue Blow Fly Calliphora vicina Robineau‐Desvoidy, 1830 is one species with potential use as a pollinator. It occurs worldwide and is easy to rear. Caged trials conducted within a hybrid carrot (Daucus carota L.) seed crop found C. vicina to be an effective pollinator. Seed yield (number and weight) from field‐grown carrot plants caged with C. vicina, but excluding all other large flower visitors (body width > 3 mm), was similar to seed yield from uncaged plants in the presence of honey bees (Apis mellifera L.) and other insects. In contrast, caged plants without C. vicina produced 10‐fold less seed. Under open field conditions, C. vicina spent an average of 71.0 s per umbel compared to 54.4 s for honey bees; however, under caged conditions, C. vicina spent more time on average per umbel (128.9 s). Counts of C. vicina and honey bees on umbels outside of cages and C. vicina inside cages found that honey bees were most abundant on days with maximum temperature > 25°C, while C. vicina was more abundant on cooler days around 20°C. C. vicina may therefore be a useful pollinator of crops grown in isolation cages for plant breeding purposes as well as in open fields when climatic conditions are less favourable for optimal honey bee activity.     

Anthecology and reproductive system of Mourera fluviatilis (Podostemaceae): Pollination by bees and xenogamy in a predominantly anemophilous and autogamous family?

The Podostemaceae are sessile hydrophytes restricted to habitats with waterfalls and seasonal flow variability. Mourera fluviatilis belongs to the family and has a disjunct distribution in the Amazon and northeastern Brazil. The following hypotheses were tested: (i) both autogamy and anemophily act on the pollination system of M. fluviatilis, and (ii) the highest reproductive success is achieved by cross-pollination. Natural populations were monitored in the rivers Pirangi and Ipojuca, northeastern Brazil. Floral visitors are the polylectic bees Apis mellifera, Trigona spinipes (Apidae), Augochlora sp. and Augochloropsis sp. (Halictidae), though only the latter three are effective pollinators. In experiments on the reproductive system and pollination there was a high percentage of fruit formation (>86%), both in treatment and control plants. Although the index of self-incompatibility is 0.86, there was a significant difference in the number of seeds produced among reproductive system treatments, and xenogamy produced more seeds. There was no significant difference in the number of penetrated ovules between control and manual cross-pollination (xenogamy) treatments, 24 h after pollination. However, there were differences among treatments, 48 h after pollination, except for the control and xenogamy treatments. The pollen tubes from cross-pollination treatments usually penetrate the micropyle in shorter time and in higher quantity. We found differences among pollination experiments, except for the control and non-emasculated treatments, and between emasculated treatments. In spite of the ambiguity of floral attributes (pedicel, filaments and anthers colors, sweet odor, reduced perianth, absence of nectar, small and dry pollen grains), wind pollination is less important for this species; what predominates instead are first allogamy mediated by bees and second self-pollination at the end of anthesis.     

Factors affecting germinable seed yield in Cypripedium calceolus var. pubescens (Willd.) Correll and Epipactis helleborine (L.) Crantz (Orchidaceae)

One of the challenges facing orchid conservationists is to get a better understanding of seed parent fecundity. This can be especially laborious for orchids whose seed is difficult to germinate. Mature seeds ofCypripedium calceolusvar.pubescens(Willd.) Correll (Orchidaceae) have been reported to require 8 weeks pre-chilling at 4°C and a further month at 20°C to induce germination, but seeds prematurely harvested at 7–8 weeks post-pollination germinate asymbiotically without chilling in less than 1 month. Mature seeds ofEpipactis helleborine(L.) Crantz (Orchidaceae) have also presented a challenge but the identification of plants whose seeds are quick and easy to germinate has provided us with a tool to study patterns of production of this seed class. Preliminary field experiments suggest that timing of pollination in these two taxa is critical for the development of seed. When seeds from capsules ofC. calceolusvar.pubescensharvested 7 weeks after pollination were examined, the proportion of fully mature embryos increased with increasing anthesis-pollination interval over the first 10 days. Paired flowers from five genets xenogamously hand-pollinated at 2-day intervals from the second day after anthesis until the flowers wilted were significantly less likely to produce fruits as the flowers aged but the flower age at which this occurred varied between genets. The germinability of seeds from different pollen and seed parent combinations was tested on eight different media formulations and over a range of post-anthesis and post-pollination intervals. Different aged seeds germinated variably, the post-anthesis interval being the most reliable predictor of germination outcomes. Intercrossing of plants ofC. calceolusvar.pubescenssuggests that seed production and germinability are maternally mediated traits. WithE. helleborine, germinable seed can be produced both by self- and by cross-pollination of selected plants but we have observed an influence of flower position in the inflorescence on self-compatibility and on the production of the easy-to-germinate seed class. The timing of pollination in these two unrelated orchids has a considerable influence upon seed production and seed quality in plants of established fecundity. These findings suggest that flower age at pollination must be considered when interpreting similar studies in the Orchidaceae.     

Contrasting effects of plant invasion on pollination of two native species with similar morphologies

Invasive plants may decrease native plant density and disrupt interactions between native plants and their pollinators. We hypothesized that invasive Solidago canadensis (Asteraceae) competes for pollination services with two confamilial species, Ixeris chinensis and Sonchus arvensis. Breeding-system studies revealed that both native species are self-incompatible. In plots with all three species we found that Solidago received the highest visitation rates. To test the hypothesis of competition for pollination in the context of reduced native density, we established 3 plots for both native species with three Solidago densities (uninvaded, 50 and 75 % invaded) and corresponding decreases in native density. We investigated the effects of varying densities of Solidago on honeybee visitation rates, number of successive visits within individual ramets, pollen-load composition on bees, and seed set. For both native species, increasing Solidago density and decreasing native density resulted in bees carrying higher ratios of Solidago pollen and in bees visiting fewer capitula prior to departing from a plant. However, for other aspects of pollination, the native species responded very differently to Solidago. With increasing Solidago and decreasing native density, Ixeris received fewer honeybee visits and produced fewer seeds, demonstrating competition for pollination, but Sonchus attracted more honeybee visits and showed a non-significant trend toward setting more seeds, suggesting facilitation. These opposing effects occurred despite similarities in the native species’ floral morphology, suggesting that the effects of invasive plants are difficult to predict. In this case the different effects may relate to Sonchus being a taller plant with larger flowers.     

REPRODUCTIVE STRATEGY OF CLEISTES DIVARICATA (ORCHID ACEAE)

In Cleistes divaricata, a hinged anther dispenses a sequence of loosely aggregated pollen tetrad masses onto the dorsal thorax of Bombus and Megachile workers. This mechanism allows more than one bee to receive pollen from a single flower. To determine the effectiveness of this strategy, plants in bud were caged and hand pollinated using pollen from sequential releases. Capsules produced from a flower's first three pollen dumps were significantly larger and heavier and contained more seeds than those produced by later pollen deposits with fewer tetrads. Decreasing pollen dosage did not affect fruit set, capsule development, individual seed weight, or percentage of healthy looking embryos per fruit. Fruit set for artificial pollinations was 93% for pollen dumps 1–3 and 97% for dumps 4–18. As set of naturally pollinated marked plants was only 38%, low frequency of pollinator visits apparently limited seed production. Efficacy of infrequent visits is maximized, however, because a flower's first pollen releases contain the most pollen, but later low-dosage dumps can produce some seeds. An unexpected cost was a higher investment of pericarp per seed in low-dosage capsules (130 ng pericarp seed^-1 fresh weight) than in high-dosage pollinations (only 27 ng pericarp seed^–1). Flower fading in plants receiving low pollen dosage was as slow as that in caged, unpollinated controls, thus increasing opportunity for additional pollination.     

矮牡丹传粉生物学的初步研究

对山西省南部矮牡丹3个居群连续两年的野外观察和实验研究表明,共有5种蜂和4种甲虫参 与矮牡丹的传粉。电镜观察和人工控制昆虫传粉试验证明,蜂类,特别是地蜂类是矮牡丹的主要传粉 者,而甲虫类只是一种不稳定的传粉者。矮牡丹花无蜜液,但可散发气味,主要以花粉吸引昆虫。矮牡 丹不存在无融合生殖,也没有自动自花结实现象,但同株异花能产生少量种子,具微弱的自交性。在花 少的居群中自然结实率与人工异交结实率近相等。矮牡丹的结实率低,平均只有近1／4的胚珠发育成种子。     

Seed dispersal and seed banks in Aloe marlothii (Asphodelaceae)

Aloe marlothii flowers during dry winter months (July–September) and produces large numbers of wind dispersed seeds. Fire disturbance in a population of several thousand A. marlothii plants at Suikerbosrand Nature Reserve, Gauteng, permitted a series of seed dispersal experiments to be conducted. Germination trials indicated that seedling emergence decreased with increased distance from a well defined aloe stand and burn area margin, with seeds dispersed up to 25 m. Flowering frequency and total seed production were positively correlated with plant height, with seed production estimated to range from 26,000 to 375,000 seeds/plant. Although a large number of seeds are produced by flowering plants the survival rate of seeds did not extend beyond the following flowering season.     

The relative importance of birds and bees in the pollination of Metrosideros excelsa (Myrtaceae)

Exclusion experiments were used to assess the effect of different pollinator groups on outcrossing and seed production in Metrosideros excelsa. The main study site was Little Barrier Island, New Zealand where indigenous bird and native solitary bees are the main flower visitors. Our results showed that native birds were more important pollinators of M. excelsa than native bees. Seed production was much higher in open pollination than in two exclusion experiments where either birds were excluded and native bees only had access to flowers, or where all pollinators had been excluded. The number of fertile seeds per capsule was 45% higher after open pollination than in treatments with bee visitation only and 28% higher than in treatments where all flower visitors were excluded. Estimated outcrossing rates were significantly higher (t_m = 0.71) for open pollination in the upper canopy (>4 m above‐ground level) where bird visitation is presumed to be more frequent than for a treatment with native bee access only (t_m = 0.40). Our results also suggest that a large proportion of seeds (66%) arise from autonomous self‐pollination when all pollinators are excluded. In four trees of a modified mainland population with predominantly introduced birds and a mixture of introduced and native bees there was no decrease in seed production for the treatment allowing bee access only, indicating that – in contrast to native bees – honeybees may be more efficient pollinators of M. excelsa. Observation of the foraging behaviour of both groups of bees showed that native bees contact the stigma of flowers less frequently than honeybees. This is likely to be a consequence of their smaller body size relative to honeybees.     

Onion pollination by blowflies and honeybees in large cages

Three experiments to investigate the effect of pollination by blowflies (Calliphora and Lucilia spp.) and honeybees (Apis mellifera) on seed yield and crossing level were made using a mixture of plants from two open-pollinated cultivars of onions (Allium cepa) in breeders' cages. No consistent differences were found between pollinators. In two experiments, fly pollination gave significantly higher yields than bee pollination but in the third, bee pollination gave slightly more seed. Crossing between cultivars, assessed by progeny testing on one cultivar, varied between 22-7 and 55-9%. Differences in crossing level attributable to the pollinators were not consistent and were not or only just statistically significant, but there were significant and substantial differences between the experiments themselves. Where more umbels were produced by the red-bulbed cultivar than by the yellow, higher crossing levels were found in the yellow cultivar. The highest crossing levels were found in the only experiment where insects were not introduced until peak flowering time, but where seed yield was comparatively low. Crossing levels were lowest where the umbel numbers were approximately equal. Individual umbels studied showed that while seed set was usually heaviest at and just before the mid-flowering date, this period could correspond with the lowest levels of crossing during the flowering period, particularly if flowering of the two cultivars was not completely synchronous. In field plots, approximately 75% of crossed seeds sown survived to give harvestable bulbs, but fewer than 50% of selfed seeds did so. In an experiment in which crossing levels from different pollinators were similar but survival levels differed significantly, it was deduced that bees performed more crossing within a cultivar than flies.     

Pollination efficiency of wild bees and hoverflies provided to oilseed rape

• 1 Declining numbers in honeybees and various wild bee species pose a threat to global pollination services. The identification and quantification of the pollination service provided by different taxa within the pollinator guild is a prerequisite for the successful establishment of nature conservation and crop management regimes.
• 2 Wild bees and hoverflies are considered to be valuable pollinators in agricultural and natural systems. Although some information on pollination efficiency of individual pollinator species is available, comparative studies of both taxa at different densities are rare. In the present study, the efficiency of the solitary mason bee Osmia rufa and two hoverfly species (Eristalis tenax and Episyrphus balteatus) as pollinators of oilseed rape Brassica napus was examined in a standardized caged plant breeding regime. Honeybee Apis mellifera colonies were used as a reference pollinator taxon.
• 3 Yield parameters responded differently to pollinator density and identity. Fruit set and number of seeds per pod increased with increasing pollinator density, although these were stronger in the mason bee than the hoverfly treatment. Weight per 1000 seeds did not respond to any pollinator treatment, indicating that seed quality was not affected. Oilseed rape yield in the highest tested densities of both pollinator taxa resulted in yield values close to the efficiency of small honeybee colonies.
• 4 Hoverflies required approximately five‐fold densities of the red mason bees to reach a similar fruit set and yield. Thus, mason bees are more efficient in plant breeding and managed pollination systems. Both natural pollinator taxa, however, are of potential value in open and closed crop production systems.

     

Pollination of greenhouse tomatoes by the Australian bluebanded bee Amegilla (Zonamegilla) holmesi (Hymenoptera: Apidae)

The pollination effectiveness of bluebanded bees of the species Amegilla (Zonamegilla) holmesi Rayment (Hymenoptera: Apidae) was evaluated in tomato plants, Lycopersicon esculentum Miller (Solanaceae), cultivated in two greenhouse chambers. Bluebanded bee pollination was compared with mechanical pollination and no supplementary pollination. Pollination effectiveness was compared between treatments by using the percentage of fruit set, fruit weight, fruit diameter, fruit roundness, and the number of seeds per fruit. Both the bluebanded bee pollination and the mechanical pollination treatments significantly increased fruit set, individual fruit weight, and diameter compared with the control treatment. Fruit were also significantly rounder and contained significantly more seeds. Positive correlations were found for fruit weight versus seed number, maximum diameter versus seed number and minimum diameter versus seed number. We conclude that the use of A. holmesi for pollinating greenhouse tomatoes in Australia may be an effective alternative to the use of mechanical pollination.     

The effect of pollination on the growth and reproduction of oilseed rape (Brassica napus)

Phenotypic plasticity is an organism's ability to alter its development and life history in response to environmental conditions. In plants, biotic and abiotic factors drive the distribution of resources between growth and reproductive traits. One such biotic factor is pollination. Studies show that wind and insect pollination enhance oilseed rape (Brassica napus) yield. However, the impact of pollination on resource allocation towards growth and reproduction is less understood. We conducted a controlled experiment to assess the effect of pollination on growth and functional reproductive traits. We compared two simulated supplementary pollen deposition methods (representing wind and insect pollination) alongside a non-supplementary control. Pollinated plants allocated resources towards growth and reproduction similarly, irrespective of deposition method. Plants receiving no supplementary pollination produced fewer seeds, allocating resources to growth, more prolific and persistent flowering, and heavier seeds. Pollinated plants had a reduced flowering period and were shorter, indicating resources were allocated to seed production rather than growth or the production of additional flowers. This allocation of resources from growth and flowering metrics can increase yield directly through increased seed production and indirectly through shorter plants and a reduced flowering period with seeds that mature earlier (agronomically beneficial traits).Wind and insect pollination can enhance and stabilise oilseed rape yield under various environmental conditions by acting in complementary ways. Since pollination limits yield in oilseed rape, it must be considered an input that can be actively managed. Successful management of pollination services requires growers to detect pollination deficits. Inadequately pollinated oilseed rape plants exhibit apparent morphological changes (e.g. taller plants that flower for longer), acting as an early warning to growers. Equipping growers with this knowledge provides them with a means of detecting deficits and thus enables them to take positive action to restore pollination services by introducing honeybees or enhancing wild pollinators.     

Pollination biology of Albizia lebbeck (L.) Benth. (Fabaceae: Mimosoideae) with reference to insect floral visitors

Indian siris, Albizia lebbeck (L.) Benth. (Fabaceae: Mimosoideae) has significant importance to human beings for its multipurpose use. Insects play a crucial role in the pollination biology of flowering plants. In the current study, we studied the pollination biology of A. lebbeck with special reference to insect floral visitors. The effectiveness of floral visitors was investigated in term of visitation frequency, visitation rate and pollen load during 2012 and 2013. In the second experiment, effect of pollinators on yield of A. lebbeck was studied in open and cage pollination experiments. Floral visitor fauna of A. lebbeck included eight-bees, two wasps, two flies, and two butterflies species. Among them, Apis dorsata, Apis florea, Amegilla cingulata, and Nomia oxybeloides had maximum abundance ranging from 349–492, 339–428, 291–342 and 235–255 numbers of individuals, respectively during two flowering seasons. A. dorsata had the highest visitation frequency (6.44 ± 0.49–8.78 ± 0.48 visits/flower/5min) followed by Amegilla cingulata (6.03 ± 0.43–7.99 ± 0.33 visits/flower/5min) and A. florea (3.61 ± 0.31–4.44 ± 0.18 visits/flower/5min). A. dorsata, N. oxybeloides, and Amegilla cingulata had the highest visitation rates (18.904 ± 1.53–11.43 ± 1.17 flower visited/min) and pollen load (15333 ± 336.22–19243 ± 648.45 pollen grains). The open pollinated flowers had significantly higher capsule weight (4.97 ± 0.21 g), seed weight (1.04 ± 0.05 g), seed numbers per pod (9.80 ± 0.34) and seed germination percentage (84.0 ± 1.78%) as compared to caged flowers. The results suggested bees especially A. dorsata, N. oxybeloides and Amegilla cingulata could be effective pollinators of A. lebbeck.     

The effects of pollination distance on seed production in three populations of Amianthium muscaetoxicum (Liliaceae)

Summary We examined the effects of varying pollination distances on seed production and its components in three populations of the perennial lily Amianthium muscaetoxicum. We performed hand pollinations using pollen from near neighbors and from plants separated by 5, 15, and 60 meters. Pollination by near neighbors reduced fruit set and the numbers of seeds per fruit in comparison to other treatments in two of the three populations; variation in pollination distance beyond near-neighbor pollination produced no effect. In the third population, in which nearneighbor pollination did not affect seed production, nearneighbor pollination reduced seed weight by 11%, compared to other pollination distances. Seed weights from the 5-, 15-, and 60-m pollination treatments did not differ, and pollination distance did not affect seed weight in the other two populations. The effects of pollination-distance treatments explained a very small proportion of the variance in seed production and seed weight. Heterogeneity among individual plants, despite full hand pollination of every plant, accounted for much more variance (by one to two orders of magnitude) than variation in pollination distance.     

The importance of bees as pollinators in the short corolla bromeliad Aechmea caudata in southern Brazil

The majority of bromeliad species are pollinated by vertebrates, mainly hummingbirds and bats. However, bees are among the most frequent visitors in some short-corolla species with ornithophilous features, but only few studies identified insects as pollinators of these bromeliads. The importance of visitors for pollination success in Aechmea caudata (Bromeliaceae) was determined through the frequency and pollination effectiveness (measured as seed set/single visit) of its visitors in a secondary Atlantic forest area in southern Brazil. Aechmea caudata is self-incompatible and therefore pollinator-dependent. A total of 16 species were recorded visiting their flowers. Bees were the most rich and frequent taxon (91% of 647 visits). Bombus morio was the most frequent species (41%). Although the floral features of A. caudata, such as scentless, tubular corollas, yellow and red flowers, and nectar secretion during the whole diurnal anthesis, are related to ornithophily, the single hummingbird species Thalurania glaucopis failed to pollinate the flowers. Its low frequency (2.5%) apparently did not promote the pollen flux between conspecific bromeliads. Pollination tests showed that no seeds developed after hummingbird visits. Seeds were formed only at flowers visited by B. morio. We discuss our findings by contrasting them with the results on the similar and sympatric A. lindenii and by emphasizing the importance of bees for pollination of bromeliads with short corolla. Our results show that pollination effectiveness together with frequency data are necessary to analyze the complex interactions between plants and their flower visitors.     

Seed yield,head characteristics and oil content in sunflower varieties as influenced by seeds from single and multiple headed plants under humid tropical conditions

Field trials were conducted during 2004 and 2005 to determine the effect of sowing seeds from plants with multiple heads and seeds from single headed plants of sunflower on seed yield, head characteristics and oil content of three widely grown open pollinated varieties (Funtua, Record and Isaanka) in the humid forest—savanna transition zone which is outside the current growing areas with a view to improving stability and sunflower productivity in this region. Seeds from multiple headed plants produced plants that flowered and matured 2–3 days later than plants from single headed plants. Apart from days to flowering in 2004, number of days to maturity and plant height were affected independently by variety and seed source factors. However, the seeds from single headed plants produced plants that recorded significantly (P < 0.01) higher head weight, head diameter, achene weight and number per head than plants from seeds of plants with multiple heads. Seed source had little effect on sunflower seed yield and oil content. However, Funtua produced significantly (P < 0.05) high seed yield (1956.0 kg ha^?1 ± 76.06) when seeds from plants with multiple heads were sown, while Isaanka recorded comparatively high seed yield from seeds of plants from either multiple (1221.0 kg ha^?1 ± 165.90) or single heads (1388.0 kg ha^?1 ± 135.84) and Record (1201.0 kg ha^?1 ± 96.97) when seeds from single headed plants were sown. Therefore, it is recommended that prospective sunflower growers who wish to cultivate Isaanka, can sow seeds from either the multiple or single head and preferably the multiple head for Funtua, and single head for Record.     

A trade-off in stand size effects in the reproductive biology of a declining tropical conifer Callitris intratropica

Because wind pollination is inefficient over longer distances, plants dependent on it may suffer Allee effects (lower individual reproductive fitness with lower density). However, at higher density, individual reproductive fitness may suffer because of intraspecific competition. We investigate density-dependent effects, via stand size, on cone and seed production and seed germinability in a conifer endemic to tropical Australia. Callitris intratropica R.T. Baker & H.G. Smith is an obligate-seeding tree that often occurs in monodominant stands embedded within savannas and on the fringes of monsoon forests. We found that isolated trees (50–300 m from stands) were taller, of broader profile, and produced approximately twice the number of cones (~407 cones per tree) as those in large stands (~173 cones per tree), suggesting that monodominance generates intraspecific competition. The number of seeds per cone (27 seeds) was not related to stand size. However, a contrasting effect in which seed germinability was higher in large stands (~20 vs. <10 % in small stands) was approximately compensatory and consistent with an Allee effect of wind pollination. The net effect of an approximately even trade-off between cone production and seed germinability was that there was neither an Allee or density-dependent effect of stand size on fitness, measured as the number of germinable seeds per tree. Nevertheless, because the likelihood of cross-fertilisation declines with distance, the ability of C. intratropica to persist as very isolated individuals may be limited.     

FLORAL BIOLOGY AND REGULATION OF SEED SET AND SEED SIZE IN THE LILY,CLINTONIA BOREALIS

We studied the reproductive ecology of Clintonia borealis, a clonal understory species, in eastern Ontario. Flowers are protogynous and require insect pollination for outcrossing and maximum seed set. Most pollination is done by nectar-gathering bumble bees. We recorded pollen deposition and flowering patterns in 1983. Flowering lasted for about 10 days in mid-June. Stigmatic pollen loads were lowest at the onset of blooming, reflecting the scarcity of male-phase flowers. Pollination increased significantly by peak bloom and subsequently remained high. However, since bees fly mostly between neighboring stems, much of the pollen transferred may have been geitonogamous. In 1983, seed set per flower was not increased by supplementing pollination or by reducing the number of fruits competing for resources per stem. Rather, flowers set more seeds (14%) only if both treatments were performed simultaneously. Seed size was increased by 25% when competitive fruits were removed and by 5% more when pollen was added under the removal treatment. Further work in 1984 showed that pollination effects may be related to changes in pollen source. Selfed flowers set fewer and smaller seeds than outcrossed ones when screened from insects and hand pollinated. Outcrossing distance had little effect on seed set or seed size. Thus, in C. borealis seed number and seed size are limited by a balance between maternal resource availability and the amount of outcrossing provided by pollinators.     

Pollinator shift to managed honeybees enhances reproductive output in a bumblebee-pollinated plant

Introduced honeybees have had a large impact on native ecosystems by disrupting native plant–pollinator interactions. However, little is known of the effect of honeybees on reproduction of bumblebee-pollinated plants. Seasonal displacement of native bumblebees by introduced honeybees (Apis mellifera and A. cerana) was observed in Pedicularis densispica, endemic to Hengduan Mountains, China, providing an opportunity for honeybee presence/absence comparisons. Five-year field surveys were conducted in one frequently disturbed population at Yila Pasture (YP). We compared pollination effectiveness (combinations of visitation rate, efficiency in pollen transfer, and potential geitonogamy) between native and introduced managed bees. The total visitation rate of native bees and subsequent reproductive output decreased progressively, but honeybee introduction resulted in at least twofold increase in visitation and 70 % increase in seed set. In general, native bumblebees, which have larger bodies and longer proboscises and spent more time probing single flowers, were more efficient than honeybees in terms of pollen removal and pollen deposition during first visits to virgin flowers. Compared with bumblebees, honeybees visited markedly fewer flowers in sequence within individual plants, potentially reducing geitonogamous pollination. Our data highlight that introduced honeybees can provide pollination service in terms of both quantity and quality for P. densispica. We suggest honeybee introduction as an effective way to augment pollination of P. densispica at disturbed and isolated sites.