Can short‐billed nectar thieving sunbirds replace long‐billed sunbird pollinators in transformed landscapes?

• Pollinator specialisation through exploitation barriers (such as long floral tubes) does not necessarily mean a lack of pollination when the favoured pollinator is rare or absent. Theory predicts that suboptimal visitors will contribute to plant reproduction in the absence of the most effective pollinator. Here I address these questions with Chasmanthe floribunda a long‐tubed plant species in the Cape Floristic Region, which is reliant on one species of pollinator, the long‐billed Malachite Sunbird. In contrast to short‐billed sunbirds, the Malachite Sunbird occurs in lower abundance or is absent in transformed landscapes. Short‐billed sunbirds rob and thieve nectar from long‐tubed flowers, but their potential contribution towards pollination is unknown.
• Experiments assessing seed set after single flower visits were performed to determine whether thieving short‐billed sunbirds can act as substitute pollinators. To determine whether short‐billed sunbirds reduce pollen limitation in transformed areas, pollen supplementation was done by hand and compared to natural fruit set.
• Short billed sunbirds are unable to act as substitute pollinators, and seed set is significantly lower in the flowers that they visited, compared to flowers visited by long‐billed sunbirds. This is substantiated on a landscape scale, where fruit production in Chasmanthe floribunda could artificially be increased by 35% in transformed landscapes, but not so in natural areas.
• These findings have important consequences for the management and conservation of long‐tubed bird‐pollinated plant species that exist in recently transformed landscapes. The potential vulnerability of specialised plant species in transformed landscapes is highlighted.

     

Territoriality and changes in resource use by sunbirds at Leonotis leonurus (Labiatae)

Summary Leonotis leonurus was studied with the aim of characterising nectar quality and quantity, and of monitoring the sunbirds' response to the resource. The flowers produced high quality nectar in low quantities. Nectar quality remained constant during the day and averaged 23.4% sucrose equivalents (an energy content of 3.8j/l). Nectar production was highest during the morning when flow rates reached a peak of 3.3 l/h. L. leonurus was visited by four species of sunbirds. In 1977 there were 7.8 visits/h to the flowers. The clump was defended by a single Olive Sunbird (Nectarinia olivacea) who defended the flowers intra- and interspecifically. On one day the territorial bird obtained approximately 57.1 kJ from the Leonotis flowers and expended 5.4 kJ on defence and 13.6 kJ overall while on the territory. Territorial behaviour and intruder pressure was a function of resource availability. When Leonotis nectar levels were high intruder pressure was intense and the territorial bird employed long chases as a defence behaviour. When nectar levels desreased intruder pressure was lower, the territorial bird chased less and employed vocalisations as a relatively inexpensive form of territorial behaviour.In 1978 there was an abundance of nectar sources in the study area due to the late onset of the dry season. Sunbirds were not territorial at Leonotis and visiting rates were lower than in 1977, averaging only 1.7 visits per hour. Instead the sunbirds concentrated on contemporaneously flowering plant species, particularly Halleria lucida.     

Experimental evidence for specialized bird pollination in the endangered South African orchid Satyrium rhodanthum and analysis of associated floral traits

The bird pollination syndrome is characterized by red, unscented flowers with dilute nectar in long nectar tubes. However, the extent to which plants with such traits actually depend on birds for seed production is seldom determined experimentally, and traits such as colour and scent production are often assessed only subjectively. We documented bird pollination and quantified floral traits in the critically endangered Satyrium rhodanthum (Orchidaceae) from mistbelt grasslands in the summer‐rainfall region of South Africa. Direct observations and motion trigger camera footage revealed amethyst sunbirds as the only pollinators, despite the presence of other potential pollinators. Experimental exclusion of sunbirds significantly reduced pollination and fruit set to near zero. Pollination success in naturally pollinated plants was close to 100% in one year, and fruit set varied from 23 to 64% in other years. Pollen transfer efficiency was 5.8%, which is lower than in related insect‐pollinated species, probably due to a tendency of birds to wipe pollinaria from their beak. Flowers of S. rhodanthum only reflect light in the red range of the spectrum, and they produce only a few aliphatic and monoterpene scent compounds at comparatively low emission rates. Nectar volume and sugar concentration varied between 2.7 and 3.7 μL and 23.7 and 25.9%, respectively. We conclude that S. rhodanthum is highly specialized for pollination by sunbirds. Colour, scent and nectar characteristics differ from insect‐pollinated Satyrium species and are consistent with those expected for bird‐pollinated flowers, and may contribute to lack of visitation by other potential long‐tongued pollinators. Habitat loss probably underlies the critically endangered conservation status of S. rhodanthum, but the specialization for pollination by a single bird species means that reproduction in this orchid is vulnerable to losses in surrounding communities of plants that subsidize the energetic requirements of sunbirds. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 177 , 141–150.     

Passerine Pollination of Rhodoleia championii (Hamamelidaceae) in Subtropical China

The pollination ecology and breeding system of the Hamamelidaceae tree species Rhodoleia championii were studied in an evergreen broad-leaved forest in Nankunshan National Forest in Guangdong Province in China. Rhodoleia championii produces lipid-rich pollen grains and dilute nectar (averaging 0.7 mL/d and 9% sugar), with nectar production peaking before 0800 h; the species is self-incompatible and does not set seed asexually. Seven species of nectar-foraging birds visited the inflorescences, with the most common visitors being Japanese white-eyes (Zosterops japonicus, Zosteropidae) and fork-tailed sunbirds (Aethopyga christinae, Nectariniidae). Bumblebees and honeybees played limited roles as pollinators. As documented by fossils from Europe, the Rhodoleia stem lineage dates back at least to the Paleocene. Bird pollination, however, is unlikely to have evolved before the Oligocene when sunbirds arrived in Europe, and pollination by Z. japonicus cannot be much older than 250,000 million years ago, when Z. japonicus diverged from its closest relative.     

African sunbirds hover to pollinate an invasive hummingbird-pollinated plant

Why do hummingbirds hover while Old World nectar‐feeding birds perch? A unique opportunity to explore this question is presented by the invasion into Africa of a plant adapted for pollination by hovering hummingbirds. Like other hover‐pollinated plants of the New World, the flowers of the tree tobacco Nicotiana glauca lack perches and are oriented towards open space. We find that Old World nectarivores, especially the malachite sunbird, Nectarinia famosa, hover 80% of the time when taking nectar from these flowers. They hover for up to 30 s, and are able to sustain this hovering lifestyle in an area where native nectar plants are absent. Nicotiana glauca greatly increases the local abundance of sunbirds compared with uninvaded areas. In turn, flowers visited by sunbirds formed significantly more capsules and set significantly more seed than sunbird‐excluded flowers, possibly facilitating the invasion. The results suggest a prominent role for plant, rather than bird traits in determining the occurrence of hover‐pollination, begging the question of why plants adapted for hover pollination do not occur outside the New World.     

Pollination and fruit‐set of Grevillea robusta in western Kenya

The floral visitors of silky oak, Grevillea robusta A. Cunn. ex R.Br., their foraging behaviour and their effects on fruit‐set were studied at Malava, western Kenya. Grevillea robusta is a popular tree for farm plantings in the eastern and central African highlands. Yield of seed has been disappointingly low in some areas and a lack of appropriate pollinators has been suggested as a possible cause. Investigations involved the monitoring of visitors on active inflorescences, assessment of the rewards available to potential pollinators, and exclusion experiments to establish the effects of various visitors on fruit‐set. The flowers are visited mainly by birds and insects. The likely pollinators of G. robusta are sunbirds (Nectarinia amethystina, N. cyanolaema, N. olivacea, N. superba and N. venusta) and white‐eyes (Zosterops kikuyuensis and Z. senegalensis). Very little aggressive behaviour between birds was recorded. No nocturnal pollinators were observed. Nectar was the major floral reward for pollinators, but is likely depleted by ants and honey bees, the foraging behaviour of which confirmed them to be nectar‐robbers. These insects hardly ever touched stigmas during their visits. Eighty‐nine per cent of bird visits were in the morning (07.00–10.00 hours) when nectar volume was highest. Inflorescences bagged to exclude birds set no fruits, and unmanipulated flowers and flowers bagged with self‐pollen set no fruits, indicating a self‐incompatibility mechanism. Control cross‐pollinated flowers displayed greatly increased fruit‐set (25.1%) compared with natural open‐pollination (0.9%). All these findings confirm the importance of cross‐pollen transfer to flowers and the necessity of pollinators for fruit‐set. Effective seed production requires activity of pollinators for self‐pollen removal and cross‐pollen deposition. Seed production stands for G. robusta should be established where flowering is prolific and bird pollinators are abundant.     

Bird pollination in South African species ofSatyrium (Orchidaceae)

Field observations showed that three South African orchid species,Satyrium carneum, S. coriifolium andS. princeps, are pollinated by sunbirds. Foraging sunbirds insert their bills into the labellum chamber of the flowers and suck nectar from the labellum spurs with their tongues. The column overarches the entrance to the labellum and pollinaria become affixed to the upper mandible of the bill. Birds often attempt to remove pollinaria by rubbing their bills against a branch, but are mostly unsuccessful due to the large plate-like viscidia which attach the pollinaria very firmly to the bill. Other modifications for bird pollination in theseSatyrium species may include the red, carmine or orange colour of the flowers, sturdy inflorescence stems used for perching and large amounts of dilute nectar in the spurs. EachSatyrium species was pollinated by several species of sunbird, and despite some differences in flowering time, occasional hybrids occur at a site whereS. carneum andS. coriifolium share the same sunbird pollinators.     

Nectar palatability can selectively filter bird and insect visitors to coral tree flowers

Secondary compounds in nectar may play a decisive role in determining the spectrum of floral visitors on plants. Flowers of the African coral tree Erythrina caffra are visited mainly by generalist passerine nectarivores, such as weavers and bulbuls. As the nectar of this species tastes very bitter to humans, it was hypothesized that secondary compounds may repel sunbirds and honeybees which are common in the same habitats yet seldom consume the nectar. We conducted choice tests using fresh nectar and both sucrose and hexose (glucose/fructose) solutions of the same concentration as the nectar. White-bellied Sunbirds (Cinnyris talatala) were repelled by nectar of both E. caffra and a related species Erythrina lysistemon, but Dark-capped Bulbuls (Pycnonotus tricolor) did not discriminate between the Erythrina nectar and control sugar solution in terms of amounts consumed. Honeybees (Apis mellifera scutellata) probed exposed droplets of E. caffra nectar and a control sugar solution at the same rate, suggesting that there is no volatile deterrent, but they immediately withdrew their proboscis far more often from the droplets of Erythrina nectar than they did from the sugar solution, suggesting that they find Erythrina nectar distasteful. These results contribute to a growing awareness that non-sugar components of nectar can play important functional roles in plant pollination systems.     

Intra‐floral resource partitioning between endemic and invasive flower visitors: consequences for pollinator effectiveness

1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators. 2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flower‐visiting insects. The former main‐pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers. 3. Ants were dominant nectar‐consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar‐foraging honeybees (Apis mellifera) strongly decreased on ant‐visited flowers, whereas pollen‐collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators. 4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant‐visited and ant‐free inflorescences. 5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds.     

Geographic variation of reproductive traits and competition for pollinators in a bird‐pollinated plant

Geographic variation in the reproductive traits of animal‐pollinated plants can be shaped by spatially variable selection imposed by differences in the local pollination environment. We investigated this process in Babiana ringens (Iridaceae), an enigmatic species from the Western Cape region of South Africa. B. ringens has evolved a specialized perch facilitating cross‐pollination by sunbirds and displays striking geographic variation in perch size and floral traits. Here, we investigate whether this variation can be explained by geographic differences in the pollinator communities. We measured floral and inflorescence traits, and abiotic variables (N, P, C, and rainfall) and made observations of sunbirds in populations spanning the range of B. ringens. In each population, we recorded sunbird species identity and measured visitation rates, interfloral pollen transfer, and whether the seed set of flowers was pollen limited. To evaluate whether competition from co‐occurring sunbird‐pollinated species might reduce visitation, we quantified nectar rewards in B. ringens and of other co‐flowering bird‐pollinated species in local communities in which populations occurred. Variation in abiotic variables was not associated with geographical variation of traits in B. ringens. Malachite sunbirds were the dominant visitor (97% of visits) and populations with larger‐sized traits exhibited higher visitation rates, more between‐flower pollen transfer and set more seed. No sunbirds were observed in four populations, all with smaller‐sized traits. Sunbird visitation to B. ringens was not associated with local sunbird activity in communities, but sunbird visitation was negatively associated with the amount of B. ringens sugar relative to the availability of alternative nectar sources. Our study provides evidence that B. ringens populations with larger floral traits are visited more frequently by sunbirds, and we propose that visitation rates to B. ringens may be influenced, in part, by competition with other sunbird‐pollinated species.     

The influence of nectar production and floral visitors on the female reproductive success of Inga (Fabaceae): a field experiment

Floral morphology, nectar secretion strategies and the contribution of pollinators to the reproductive success of plants provide important clues regarding the levels of generalization or specialization in pollination systems. Anthesis throughout the day and night allows flowers to be visited by diurnal and nocturnal pollinators, promoting generalization or specialization. We studied three species in the diverse tropical genus Inga to: (1) quantify the response of flowers to successive nectar extractions and (2) determine the contribution of diurnal and nocturnal floral visitors to female reproductive success. Inga flowers could be clearly distinguished mainly on the basis of the staminal tube diameter and the quantities of filaments and pollen grains. Successive nectar removals led to a decrease of 60% in the total nectar secretion in I. vera and to increases of 20% in I. ingoides and 10% in I. striata. Despite these differences, the studied Inga spp. exhibited similar patterns of visitation rates and shared diurnal and nocturnal pollinators. Nocturnal pollinators contributed ten times more than diurnal pollinators to the female reproductive success of Inga. Floral morphology, nectar secretion patterns and pollination ecology data suggest an evolutionary trend towards specialization for nocturnal pollinators in Inga spp. with crepuscular or nocturnal flowers. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 230–245.     

Diverse pollination systems of the twin-spurred orchid genus Satyrium in African grasslands

The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs.     

Pollinators shift to nectar robbers when florivory occurs,with effects on reproductive success in Iris bulleyana (Iridaceae)

• Studies have indicated that florivory and nectar robbing may reduce reproductive success of host plants. However, whether and how these effects might interact when plants are simultaneously attacked by both florivores and nectar robbers still needs further investigation.
• We used Iris bulleyana to detect the interactions among florivory, nectar robbing and pollination, and moreover, their effects on plant reproductive success. Field investigations and hand‐pollination treatments were conducted on two experimental plots from a natural population, in which Experimental plot was protected from florivores and Control plot was not manipulated.
• The flower calyx was bitten by sawflies to consume the nectary, and three bumblebee species were pollinators. In addition, the short‐tongued pollinator, Bombus friseanus, was the only robber when there was a hole made by a sawfly. The bumblebee had significantly shortened flower handling time when robbing, as compared to legitimate visits. Pollinator visitation and seed production decreased significantly in damaged flowers. However, seed production per flower after supplementary hand‐pollination did not differ significantly between damaged and undamaged flowers. Compared to the Experimental plot, bumblebees visited fewer flowers per plant in a foraging bout in the Control plot.
• The flowers damaged by florivory allowed B. friseanus to shift to a nectar robber. Florivory and nectar robbing collectively decreased plant reproductive success by consuming nectar resources, which may reduce attractiveness to pollinators of the damaged flowers. However, the changes in pollinator behaviour might be beneficial to the plant by reducing the risk of geitonogamous mating.

     

Pollination of the red-hot poker Kniphofia laxiflora (Asphodelaceae) by sunbirds

Most of the species in the large African genus Kniphofia have floral traits that conform to the bird pollination syndrome, however there has been very little empirical work to confirm that birds are effective pollinators of Kniphofia species. From selective exclusion experiments, behavioural observations and pollen load analyses, we identified Amethyst Sunbirds (Chalcomitra amethystina) and Malachite Sunbirds (Nectarinia famosa) as the primary pollinators in two populations of Kniphofia laxiflora, with bees playing a smaller role. Bird visitors obtain moderate volumes (∼ 9 µl) of relatively concentrated (∼ 15%) hexose-rich nectar in the flowers. This species is shown to be genetically self-incompatible, and thus reliant on pollinator visits for seed set. Although mountain pride butterflies (Aeropetes tulbaghia) have been identified as important pollinators of this species at two other populations, they did not occur at the two populations we studied.     

Promiscuous pollinators—Evidence from an Afromontane sunbird–plant pollen transport network

Sunbirds play a major role in the pollination of Old World nectivorous plants. However, with the exception of the Cape Floristic Region there is a major knowledge gap around African nectivore interaction networks—a stark contrast from the abundance of neotropical hummingbird–plant networks. Here, we describe a sunbird pollen transfer network (PTN) which we use in conjunction with a sunbird flower visitation network (FVN) to explore levels of sunbird specialization within an Afromontane forest habitat. Both networks were generalized compared with similar‐sized hummingbird networks, reflecting the wide range of flower types visited, the generalist diet, and bill characteristics of sunbirds. Three sunbird species from the genus Cinnyris accounted for 85% of flower visits and 77% of all pollen transported. Of the 17 plant species across both networks, 15 are predominantly pollinated by insects while Anthonotha noldeae (Fabaceae–Caesalpinioideae) and Globimetula braunii (Loranthaceae) depend on sunbirds for seed set. Sunbird species average bill lengths varied between 14.5 mm (the variable sunbird) and 23.6 mm (the Green‐headed Sunbird), but, while more pollen was carried on longer bills, we found no evidence for a relationship between bill length and type of flower visited. Both networks were nested. Some specialization was observed in both networks although this does not appear to be driven much by sunbird–flower trait matching. Overall, our results suggest that in contrast to nectivores elsewhere, factors such as phenology and/or environment, rather than morphology, may play important roles in limiting potential sunbird–flower interactions and need further investigation.     

Pollination Ecology and Effect of Nectar Removal in Macleania bullata (Ericaceae)1

The floral syndrome of Macleania bullataYeo (Ericaceae) reflects its adaptation to hummingbird pollination. Its flowers, however, are subject to high levels of nectar robbing. I examined the floral visitor assemblage of M. bullata in a tropical montane wet forest in southwestern Colombia, focusing on the behavior of the visitors. I also tested for the presence of nocturnal pollination and the effects of nectar removal on new nectar production. The principal floral visitors were the nectar robbing hummingbirds Ocreatus underwoodii (19.1% of visits) and Chlorostilbon mellisugus (18.9%). Only two species of long–billed hummingbirds visited the flowers of M. bullata as “legitimate” pollinators: Coeligena torquata (14.7% of visits) and Doryfera ludoviciae (14.3%). The remaining visits constituted nectar robbing by bees, butterflies, and other species of hummingbirds. Nocturnal pollination took place, although fruit set levels were 2.4 times higher when only diurnal pollination was allowed as opposed to exclusively nocturnal pollination. Nectar robbers removed floral nectar without pollinating the flower. Treatments of experimental nectar removal were carried out to examine if flowers synthesize more nectar after nectar removal. Nectar removal increased the total volume of nectar produced by each flower without affecting sugar concentration. Thus, nectar robbing can impose a high cost to the plants by forcing them to replace lost nectar.     

Pink flower preference in sunbirds does not translate into plant fitness differences in a polymorphic Erica species

Bird-pollinated plants typically have reddish flowers, but it is not clear whether this trait can be attributed to selection by birds. Here we experimentally test for the first time the foraging behaviour of sunbirds in relation to flower colour, using the Orange-breasted Sunbird Anthobaphes violacea (Nectariniidae) and the colour dimorphic Erica perspicua (Ericaceae). Pink and white flower morphotypes co-flower in intermixed populations and have similar nectar volumes and concentrations. Using floral arrays in a field aviary, we found that sunbirds preferred pink flowers; 95 % of their first choices were to pink inflorescences and they visited and probed more pink inflorescences and flowers, respectively. We also tested for flower constancy (the tendency to move between same colour rather than different colour morphotypes), but found no evidence for this in the sequence of their foraging choices, indicating that this mechanism did not maintain flower colour differences in sympatry. There was evidence for optimal foraging: 80 % of moves were to adjacent inflorescences. Unexpectedly, the preference for pink flowers observed in the aviary did not translate into a female fitness advantage for this morphotype in the field, since no difference is found in natural pollination rate, fruit or seed set. This may be because the minimization of flight distances between plants is the primary factor in sunbird foraging choices, overriding their colour preference. Antagonistic nectar robbers did not act as a selective force on the polymorphism, since nectar-robbing rates were equal between white and pink morphotypes in the field.     

Bumble bee behavior and selection on flower size in the sky pilot,Polemonium viscosum

Summary In alpine Polemonium viscosum, plants having sweet-scented flowers are primarily pollinated by queens of the bumble bee species, Bombus kirbyellus. In this paper we ask whether two aspects of the pollination effectiveness of bumble bees, visitation rate and pollination efficiency, vary significantly with flower size in sweet-flowered P. viscosum.(i) Bumble bees visited plants with large flowers on 80–90% of encounters, but visited those with smaller flowers on only 49% of encounters. (ii) However, the gain in pollination that large-flowered plants obtained via increased visitation was countered in part because bumble bees deposited fewer outcross pollen grains per visit on stigmas of large flowers than on those of small ones. When both visitation rate and pollination efficiency are taken into account, the predicted value of a single bumble bee encounter declines from 1.06 seeds for flowers larger than 18 mm in diameter to 0.55 seeds for flowers smaller than 12 mm in diameter. Our results suggest that bumble bee pollinators of P. viscosum prefer flower morphologies that are poorly suited for precise pollination. Such behavioral complexities are likely to place constraints on the evolution of optimal floral design.     

Floral sexual dimorphism and flower choice by pollinators in a nectarless monoecious vine Akebia quinata (Lardizabalaceae)

We investigated the pollination system and movement patterns of pollinators among flowers of the nectarless, monoecious vine Akebia quinata in natural populations and experimental floral arrays. Female flowers did not offer any rewards for pollinators and were larger than male flowers. Pollinators of A.quinata , such as small solitary bees and hoverflies, clearly discriminated between male and female flowers. Hoverflies always visited male flowers and rarely visited female flowers. In contrast, solitary bees tended to visit female flowers first when entering the array, but then switched to male flowers within the same foraging bout. This tendency disappeared when the sepal size of female flowers was experimentally reduced to the size of male flowers. Thus, observed non-randomness in flower choice by solitary bees may be caused by female>male sexual dimorphism and may increase the chance of cross-pollination and lower the probability of geitonogamous pollination in a single visit to a plant. Therefore, floral sexual dimorphism in A.quinata is considered to be an adaptation for deceptive pollination associated with discriminating pollinators.     

Reproductive Ecology of Rhynchanthus beesianus W. W. Smith （Zingiberaceae）in South Yunnan, China： A Ginger with Bird Pollination Syndrome

Rhynchanthus beesianus W. W. Smith （Zlnglberaceae） Is an eplphytlc tropical ginger with a very conspicuous floral display, but almost no fruit set under field conditions. The reproductive ecology encompassing phenology, floral biology, and pollination and breeding systems was Investigated In an evergreen broadleaved forest In Yunnan Province, Southwest China. The flowers possess a typical bird pollination syndrome, but no effective pollinators were observed during 138 h of observation. Female Black-breasted Sunbird （Aethopyga saturata） and bumblebees visited R. beesianus regularly, but they all played roles as nectar robbers. No fruit was found In the bagging treatment, and fruit set following manual self-pollination （（57.55 ± 4.08）%） was comparable with cross-pollination （（64.32 ± 4.42）%）, suggesting that R. beeslanus is self-compatible but spontaneous self-pollination In this species does not occur. Seed set of open-pollination （（26.42 ± 3.11）%） was significantly lower than manual self-pollination （（73.41± 4.16）%） and cross-pollination （（75.56 ± 4.52）%）, confirming that R. beeslanus was dependent on animals for fertilization and suffered a serious pollinator-limitation.