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The study of the performance of animal pollinators has expanded in recent decades mainly due to the concern on crop productivity. Among insects, bees are the main pollinators of most Angiosperm species. The aim of this paper was to study the effect of bee body size on the pollination of Cucurbita maxima Duch. (Cucurbitaceae) var. zapallito crops. We quantified stigmatic pollen deposition by single visits of bee species with different body sizes. Bee species were classified into four categories accordingly to their intertegular distance: Very small (≤ 1.7 mm), Small (1.71 mm < 2.7 mm), Medium (2.71 mm < 3.7 mm) and Large (> 3.71 mm). Fifteen bee species belonging to the Apidae and Halictidae families were observed depositing pollen on the stigmas of C. maxima. The number of pollen grains deposited and the probability of pollen deposition per visit increased significantly with body size. Large bees Xylocopa augusti and Bombus pauloensis were the most efficient species at depositing pollen on stigmas followed by medium-sized bees Eucera fervens and Apis mellifera. The results show that several wild bee species play an important role in the pollination of C. maxima crops. This research provides baseline data for the design of pollination studies to develop strategies to optimize pollination of this crop. [ABSTRACT FROM AUTHOR]

Oceanic islands are places where biological assemblages are relatively simple, as compared to the mainland. On islands, however, pollinator assemblages may to be composed of a taxonomically disparate group of organisms (e.g. insects, lizards, and birds), some of them with opportunistic nectar-feeding behaviour. Here we investigated some components of pollination effectiveness of Lotus maculatus (Fabaceae), an endangered Canary Islands endemic. In a flower exclusion experiment, we bagged flowers and compared their subsequent fruit and seed set to that of control flowers. Number of interactions with vertebrate and invertebrate flower visitors was counted and it was recorded whether interactions were legitimate (potentially pollinating) or non-legitimate (nectar robbing). Additionally, we estimated pollen loads on lizards and looked for any relationship between reproductive success of individual plants and number of visits made by the top three flower-visiting species (in terms of both frequency of occurrence at censuses and number of floral visits). Bagged flowers fruited less and with fewer seeds than control flowers. The only observed flower-visiting vertebrate was the Tenerife lizard Gallotia galloti, whose interactions were always legitimate and with around a half of captured individuals carrying pollen grains. The most frequent flower-visiting insect was the honeybee Apis mellifera followed by the solitary bee Lasioglossum arctifrons. The honeybee, however, was only a nectar robber, and the solitary bee was not an effective pollinator, but rather a pollen gatherer. Fruit set by individual plants was positively related only to frequency of visits by the lizard. Thus, the lizard seems to play a key role in the conservation management of L. maculatus.

Intensification of forest management to increase production of biomass has resulted in considerable habitat degradation with negative impacts on insect biodiversity, including beneficial insect groups such as pollinators. Yet, little is known about how reliant forest understory plants, such as bilberry (Vaccinium myrtillus), are on insect pollinators for reproduction. Here, we quantified the structure of the bilberry flower visitor community, compared the pollination effectiveness of the most common pollinators, and experimentally quantified bilberry pollination dependency. The bilberry pollinator community was comprised of several bee and hoverfly taxa. Bumblebees were the most important pollinators due to their high abundance and pollination effectiveness. Other bees, in particular, Andrena spp., and to a smaller extent, hoverflies, were also effective pollinators. Furthermore, bilberry was strongly pollen-limited, with only 40% of open-pollinated flowers setting fruit. Bilberry supports a diverse flower visitor community within hemi-boreal forests, for which it is highly dependent for reproduction. Given the ecological and cultural value of bilberry, the importance of insect pollinators for understory plants should be considered within forest management strategies.

Abstract The brown honeyeater (Lichmera indistincta) is a common bird species in Australia and is a pollinator of many native plant species but there are no records demonstrating evidence of effective pollination by honeyeaters in commercial cropping systems. We observed L. indistincta visiting rabbiteye blueberry flowers at a commercial berry orchard on the Mid North Coast of New South Wales and evaluated their capacity to transfer pollen. We did this by bagging flowers to prevent visitation prior to anthesis; after anthesis, we unbagged the flowers and waited for L. indistincta visits. After a single visit, we collected the stigma and mounted it on a slide to evaluate stigmatic pollen load. We observed the birds visiting blueberry flowers and foraging on nectar. We also found that L. indistincta deposited similar amounts of pollen to other common insect pollinator species, such as honeybees and stingless bees. As the commercial berry orchard blocks are surrounded by diverse remnant vegetation, we hypothesize that the vegetation is likely providing habitat for these birds. Our results indicate that berry growers with management practices that protect and support remnant vegetation surrounding blueberry orchard blocks may benefit from higher blueberry pollination services by supporting diverse pollinators within fields.

• Managing pollination services requires specific targets to maximize production. • Protocols for hive management in crops are not based on ecological knowledge. • Quality of beehive for crop pollination affects productivity and optimal colonies ha−1. • Maximizing blueberry production requires 7 high-quality honeybee hives ha−1. • Reaching similar levels of production with low-quality hives requires 20 colonies ha−1. Animal pollination is essential to guarantee the economic viability of pollination-dependent crops, and honeybees (Apis mellifera L.) play a central role as the most used species worldwide for pollination service management. Despite its importance, recommendations on honeybee hive stocking density are based on rules of thumb that assume hives as standardized units and do not consider the contingencies of the crop's pollen deposition demand. We developed a mechanistic simulation model to assess the consequences of variant hive quality and stocking density scenarios for blueberry productivity per hectare. To do so, we used Bayesian models, field experiments and secondary information to parametrize the simulation and estimate flower visitation rate, pollen deposition, and fruit production at the crop level. We found that maximizing pollen deposition at the crop level can be achieved with seven high quality-hives ha−1 (20000 bees colony−1), whereas reaching similar levels of pollination with conventional hives (10000 bees colony−1) would require 20 hives ha−1. Also, optimal hive stocking densities to maximize blueberry yield ha−1 needs four high quality-hives ha−1, whilst similar levels of productivity could be reached with 20 conventional colonies ha−1. From an economic and productive perspective, a lower unit rental price for conventional hives compensates for the use of less, but more expensive, high quality hives. Therefore, deciding using either low or high-quality hives should be based on, for instance, the logistic implications of using ∼2.5 more hives ha−1 and the consequences of using colonies with a poorer sanitation state for pollination service stability. Our work set the basis for a more biological and evidence-based protocol for honeybee hive management in blueberry crops. Indeed, integrating honeybee and blueberry pollination ecology, we provide a pragmatic approach to maximize crop productivity based on the minimum beehive stocking densities that optimize pollen deposition and crop yield ha−1 depending on hive's quality. Knowing such a minimum allows for reduced operation costs for farmers, lower uncertainty of pollinators contribution to crop productivity and the risk of undesirable pollination scenarios, and helps to limit the potential negative impacts of saturating ecosystems with honeybees. [ABSTRACT FROM AUTHOR]

Plant–lizard interactions are still poorly studied, despite lizards are known to interact with flowering plants in many parts of the world. They are commonly reported on islands although the number of documented interactions has also increased in mainland, mostly in isolated environments. In this study, we first performed a global review to explore whether lizard–flower and lizard double mutualistic interactions in continents occur in environments similar to those of islands. Then, we aimed at explaining the factors driving the current distribution of such interactions worldwide. To do this, we considered four environmental factors (latitude, altitude, rainfall and temperature), and phylogeny and body size of lizards that may influence flower visitation. Furthermore, we investigated for the first time the functional role (legitimate visit versus florivory) of lizards in plant reproduction and the conditions under which each type of interaction occurs. Finally, we explored the factors influencing the distribution of lizard double mutualisms worldwide. We recorded a total of 452 lizard–flower interactions (ca 3.4% and 0.1% of the extant lizard and plant species, respectively). Lizard–flower interactions were more frequently recorded on islands (79%) regardless of phylogeny and lizard body size, whereas in mainland the number of interactions increased with altitude. Our analyses also revealed that only 20% of all interactions confirmed pollination effectiveness and a strong association of the type of interaction with environmental factors and species traits. Regarding the distribution of lizard double mutualisms, we found a positive effect of island and rainfall, but a decrease in their occurrence with latitude, altitude, temperature and body size. We predict that mutualistic plant–lizard interactions will be increasingly documented, especially in isolated environments (both on islands and continents), which will help us to better understand the biological patterns of this phenomenon and the mechanisms underlying them. [ABSTRACT FROM AUTHOR]

The western honey bee (Apis mellifera) is the most frequent floral visitor of crops worldwide, but quantitative knowledge of its role as a pollinator outside of managed habitats is largely lacking. Here we use a global data set of 80 published plant-pollinator interaction networks as well as pollinator effectiveness measures from 34 plant species to assess the importance of A. mellifera in natural habitats. Apis mellifera is the most frequent floral visitor in natural habitats worldwide, averaging 13% of floral visits across all networks (range 0 – 85%), with 5% of plant species recorded as being exclusively visited by A. mellifera. For 33% of the networks and 49% of plant species, however, A. mellifera visitation was never observed, illustrating that many flowering plant taxa and assemblages remain dependent on non-A. mellifera visitors for pollination. Apis mellifera visitation was higher in warmer, less variable climates and on mainland rather than island sites, but did not differ between its native and introduced ranges. With respect to single-visit pollination effectiveness, A. mellifera did not differ from the average non-A. mellifera floral visitor, though it was generally less effective than the most effective non-A. mellifera visitor. Our results argue for a deeper understanding of how A. mellifera, and potential future changes in its range and abundance, shape the ecology, evolution, and conservation of plants, pollinators, and their interactions in natural habitats.

Mango is an economically important fruit crop in tropical regions, including parts of Australia. However, the contribution of native flower visitors to mango pollination and fruit set is currently understudied. We studied cv. Kensington Pride (KP) in the Northern Territory (NT) of Australia to assess the overall contribution of insect pollinators to fruit set through pollinator exclusion treatments – open pollination, total pollinator exclusion and large pollinator exclusion (>5 mm). We also compared diurnal patterns in insect visitation with mango phenology and determined the pollination effectiveness and efficiency of flower visitors based on visitation rates, foraging behaviour and pollen deposition. At 45 days after the first pollinator survey, the number of fruits per panicle in open and large pollinator exclusion treatments was not significantly different from one another, despite large pollinator exclusion panicles receiving less than half of the number of insect visitations. Furthermore, open and large pollinator exclusion treatments had 28- and 30-times higher numbers of fruits per panicle than the total pollinator exclusion treatment, respectively, showing the importance of insect pollination. The native stingless bee Tetragonula mellipes was the most frequent visitor (7906 visits, 62.7 %), followed by a hover fly Mesembrius bengalensis (2404 visits, 19.1 %). Tetragonula mellipes had the highest mango pollen loads on their bodies and deposited more pollen grains on stigmas per visit than other flower visitors, and contributed 75.5 % to the mango pollination services, about 4.5 times more than the next most important pollinator (M. bengalensis : 16.8 %). Our results suggest that T. mellipes efficiently pollinate mango flowers in the NT when wild colonies are abundant in the native vegetation adjacent to the crop. Placing T. mellipes hives in the centre of larger mango orchards may increase pollination services and potentially farm productivity by ensuring good pollination towards the centre of orchard blocks. • The contribution of wild insect pollination to the Kensington Pride mango fruit set was assessed. • The native stingless bee Tetragonula mellipes was the most efficient pollinator, outperforming hover flies and honey bees. • Open and large pollinator exclusion treatments had 28 and 30 times more fruits than total pollinator exclusion treatment, respectively. • Excluding large pollinators such as honey bees and hover flies did not affect the resulting fruit set. • The number of fruits per panicle increased with T. mellipes visits. [ABSTRACT FROM AUTHOR]

Many crop plants rely on insect pollination, particularly insect-pollinated crops which are functionally dioecious. These crops require insects to move pollen between separate plants which are functionally male or female. While honey bees are typically considered the most important crop pollinator species, many other insects are known to visit crops but the pollination contribution of the full diversity of these flower visitors is poorly understood. In this study, we examine the role of diverse insect pollinators for two kiwifruit cultivars as model systems for dioecious crops: Actinidia chinensis var. deliciosa 'Hayward' (a green-fleshed variety) and A. chinensis var. chinensis 'Zesy002' (a goldfleshed variety). In our round-the-clock insect surveys, we identified that psychodid flies and mosquitoes were the second and third most frequent floral visitors after honey bees (Apis mellifera L), but further work is required to investigate their pollination efficiency. Measures of single-visit pollen deposition identified that several insects, including the bees Leioproctus spp. and Bombus spp. and the flies Helophilus hochstetteri and Eristalis tenax, deposited a similar amount of pollen on flowers as honey bees (Apis mellifera). Due to their long foraging period and high pollen deposition, we recommend the development of strategies to boost populations of Bombus spp., Eristalis tenax and other hover flies, and unmanaged bees for use as synergistic pollinators alongside honey bees. [ABSTRACT FROM AUTHOR]

Many crop plants rely on insect pollination, particularly insect-pollinated crops which are functionally dioecious. These crops require insects to move pollen between separate plants which are functionally male or female. While honey bees are typically considered the most important crop pollinator species, many other insects are known to visit crops but the pollination contribution of the full diversity of these flower visitors is poorly understood. In this study, we examine the role of diverse insect pollinators for two kiwifruit cultivars as model systems for dioecious crops: Actinidia chinensis var. deliciosa ‘Hayward’ (a green-fleshed variety) and A. chinensis var. chinensis ‘Zesy002’ (a gold-fleshed variety). In our round-the-clock insect surveys, we identified that psychodid flies and mosquitoes were the second and third most frequent floral visitors after honey bees (Apis mellifera L), but further work is required to investigate their pollination efficiency. Measures of single-visit pollen deposition identified that several insects, including the bees Leioproctus spp. and Bombus spp. and the flies Helophilus hochstetteri and Eristalis tenax, deposited a similar amount of pollen on flowers as honey bees (Apis mellifera). Due to their long foraging period and high pollen deposition, we recommend the development of strategies to boost populations of Bombus spp., Eristalis tenax and other hover flies, and unmanaged bees for use as synergistic pollinators alongside honey bees.

Female and male solitary bees usually differ in their behavioral and morphological attributes and consequently in their pollination effectiveness. The current study was carried out at the research farm of The Islamia University of Bahawalpur, Pakistan, to compare the foraging behavior and pollination efficiency of female and male Andrena savignyi Spinola, 1838 on Brassica campestris. The impact of different environmental factors (temperature, relative humidity, light intensity and wind speed) on foraging behavior was also studied. Andrena savignyi was the most abundant floral visitor of B. campestris and comprised 52.17% of the floral visitors. Female individuals fed on both nectar and pollen while male fed on nectar. Visitation frequency, visitation rate, pollen harvest and pollen deposition of females were significantly higher than that of males because of their larger size and more dry weight. The maximum abundance of females was recorded at 12:00 pm followed by a sharp decline until 4:00 pm whereas males attained their maximum abundance at 2:00 pm. The female pollinated flowers resulted in greater pod weight, pod length, number of seeds per pod, seed weight per pod and germination percentage than the males. Our results suggest that females of A. savignyi deliver better pollination of B. campestris than males in terms of its reproductive success and germination percentage. Future studies should emphasis on exploring the biology and ecology of A. savignyi with special focus of its artificial nesting.

Pollen limitation and its drivers along altitudinal clines form a controversial topic, highlighting the need for more studies and in different biomes. We tested the hypothesis that the populations of a predominantly bee-pollinated plant are pollen-limited along elevations and examined whether this is related to bee visitation rate. For two years, we studied flower visitation, pollen limitation and mating system using five populations of Stachys germanica L. occurring between 327 and 1936 m a.s.l. on Mt. Olympus, Greece. S. germanica showed moderate to high self-compatibility, low spontaneous self-pollination and low pollen limitation across all altitudes and years. Bumblebees were the dominant pollinators; their visitation increased with altitude and was positively correlated with seed set and negatively correlated with pollen limitation. The opposite trend was found for the visitation by other pollinators. Seed mass was independent of visitation. Low pollen limitation is evidently due to high bumblebee visitation along the altitude, whereas seed mass could be linked to resource availability or environmental conditions. Our findings underline the functional role of bumblebees on Mediterranean mountains, and the need to focus on bumblebee conservation on this legendary mountain. [ABSTRACT FROM AUTHOR]

Many insect species provide essential pollination services. However, the amount of pollen deposited onto a stigma when visiting a flower ('single visit pollen deposition', SVD) can vary greatly among taxa depending on morphological traits of pollinators. Further, SVD is commonly measured using one of two methods ('static': waiting for an insect to visit a flower present on plant, and 'active': removing the flower and presenting it to a flower visitor) that may also differ in their effectiveness.To gain a more comprehensive understanding of how SVD compares among pollinators, we conducted a hierarchical meta‐analysis using data from 28 studies identified by a systematic review. These contained SVD data for 94 bee and 33 fly taxa (hereafter 'wild pollinators'), across 30 plant species from which we included 127 observations. In the analysis of each study, we used the western honey bee Apis mellifera as a comparator species.Wild pollinators deposited more pollen onto stigmas per single visit than honeybees, and those with larger body deposited significantly more pollen than smaller ones. Of the two methodological approaches to assess SVD, 'static' versus 'active', we found no significant difference regarding the amount of deposited pollen.Synthesis and applications. Our meta‐analysis highlights the breadth of wild pollinators that contribute to pollination effectiveness via their delivery of pollen to many crop and non‐crop plant species. However, just 25% of the observations assessed the amount of pollen deposited by fly species. Our findings point to the need to further quantify the pollination effectiveness of non‐bee pollinators as studies have largely focused on managed and wild bee species. [ABSTRACT FROM AUTHOR]

Nocturnal pollination plays an important role in sexual plant reproduction but has been overlooked, partially because of intrinsic difficulties in field experimentation. Even less attention has received the effect of within-inflorescence spatial position (distal or proximal) on nocturnal pollinators of columnar plants, despite numerous studies examining the relationship between such position and reproductive success. Woody endemic Echium simplex possesses large erect inflorescences bearing thousands of flowers which are visited by a wide array of diurnal and nocturnal animals. In this study, we identified nocturnal visitors and compared their pollination effectiveness with that of diurnal pollinators in different inflorescence sections by means of selective exclosures in NE Tenerife (Canary Islands). Nocturnal visitors included at least ten morphospecies of moths (such as Paradrina rebeli and Eupithecia sp.), two coleopteran species (mainly Alloxantha sp.), neuropterans (Chrysoperla carnea), dictyopterans (Phyllodromica brullei), dermapterans (Guanchia sp.) and julidans (Ommatoiulus moreletii). In general, plants excluded from pollinators set less fruits than open-pollination (control) plants which set fruits homogeneously across sections. Diurnally pollinated plants set more fruit in their upper parts whereas nocturnally pollinated plants set fruit in both upper and bottom sections. We conclude that although the frequency and diversity of diurnal pollinators is far higher than that of nocturnal pollinators, both exhibit different foraging behaviour that generates complementary effects on the reproductive success of E. simplex. [ABSTRACT FROM AUTHOR]

En esta investigación estimamos la efectividad de polinización en tres poblaciones de Alstroemeria ligtu. Los resultados muestran que Lasia es el género de polinizador más frecuente, cuya efectividad varía entre poblaciones. Proponemos que la efectividad de polinización puede responder a condiciones locales que varían en el rango de distribución de la planta y sus polinizadores.

Islands harbor a considerable portion of global biodiversity and endemic biota, and also are the recipients of the largest proportional numbers of alien invaders. Such invaders may jeopardize the performance of native species, through either their direct or indirect effects. In this study, we investigated the reproductive ecology of the endemic scrambling perennial herb Canarina canariensis in remnants of the former thermosclerophyllous woodland of Tenerife (Canary Islands), assessing how two widespread alien invasive species, the honeybee (Apis mellifera) and the black rat (Rattus rattus), affect its reproductive success. Apis mellifera visits its flowers whereas the black rat consumes both its flowers and fruits. Here, we compared the pollination effectiveness of different animal guilds (vertebrates vs insects) by means of selective exclosures and determined the level of floral herbivory. Three bird species (Phylloscopus canariensis, Cyanistes teneriffae and Sylvia melanocephala), a lizard (Gallotia galloti) and two insects (A. mellifera and the butterfly Gonepteryx cleobule) were the main flower visitors. Phylloscopus canariensis was the most frequent visitor in the early flowering season whereas A. mellifera predominated in the flowers during mid and late flowering periods. Birds increased fruit set, whilst lizards and insects had a negligible effect. Rats consumed about 10% of the flowers and reduced fruit set to one third. Besides contributing little to plant reproduction, A. mellifera might interfere with bird pollination by depleting flowers of nectar. We conclude that both alien species can threaten C. canariensis reproduction and hence population sustainability in the thermosclerophyllous vegetation. Apis mellifera, in particular, may become especially detrimental if apiculture keeps expanding, or if this bee becomes active earlier in the season due to global warming. [ABSTRACT FROM AUTHOR]

Summary: The pollination effectiveness of a flower visitor has traditionally been measured as the product of a quantity component that depends on the frequency of interaction and a quality component that measures the per‐visit effects on plant reproduction. We propose that this could be complemented with a genetic component informing about each pollinator's contribution to the genetic diversity and composition of the plant progeny.We measured the quantity and quality components of effectiveness of most pollinator functional groups of the generalist herb Erysimum mediohispanicum. We used 10 microsatellite markers to calculate the genetic component as the diversity of sires among siblings and included it into the calculation of the pollination effectiveness.Functional groups varied in the quantity and quality components, which were shown to be decoupled. Functional groups also differed in the genetic component. This component changed the estimates of pollination effectiveness, increasing the differences between some functional groups and modifying the pollination effectiveness landscape.We demonstrate that including the genetic component in the calculation of the pollination effectiveness may allow a more complete quantification of the contribution of each pollinator to the reproductive success of a plant, providing information on its mating patterns and long‐term fitness. [ABSTRACT FROM AUTHOR]

Oceanic island ecosystems favour the appearance of novel interactions as a consequence of their depauperate and disharmonic flora and fauna. We investigated Echium simplex, endemic to the Anaga Biosphere Reserve in NE Tenerife, Canary Islands, belongs to the Canarian bird–flower element.Along two flowering seasons, we studied the breeding system of E. simplex, identified the floral visitors and compared the pollination effectiveness of different animal guilds (insects versus vertebrates) by means of selective exclosures.E. simplex is self‐compatible but selfing significantly reduced fruit set. The flowers were visited by five bird species (mostly Phylloscopus canariensis and Serinus canarius, but also Cyanistes teneriffae, Sylvia atricapilla and Sylvia melanocephala), a lizard species (Gallotia galloti) and over a hundred insect species (mainly hymenopterans and coleopterans). Flying insects increased fruit set whereas small flower dwellers (mostly beetles) decreased both fruit and seed set. Vertebrates had a negligible effect on reproductive success.We conclude that although the floral resources provided by E. simplex may be important to some vertebrate species, these do not appear to contribute to increase fitness of the plant, which was more dependent upon flying insects for fruit and seed set. We additionally found that plant reproductive structures are heavily damaged by feral goats, which threaten the maintenance of this Canarian endemic species. [ABSTRACT FROM AUTHOR]

Heterostyly is a floral polymorphism consisting in the presence of two morphs in the population that differ reciprocally in the position of their sexual organs. Heterostylous species depend on visitors to produce fruits, but the efficiency of insect species as pollinators greatly varies and depends on the morph visited. The aim of the present study was to determine the effect of a single visit by the bees Apis mellifera and species of Augochloropsis on the fruit set of the distylous species Psychotria carthagenensis.After a single visit from each bee species, flowers were bagged to monitor the fruit set. Pollination effectiveness between pollinators and morphs was compared. The results of the experiments were compared with data from manual intermorph cross-pollination using the G test. There were no significant differences in the fruit set between treatments (insect visit and cross-pollination), and between flowers visited by Augochloropsis spp. and flowers visited by A. mellifera. Our results suggest that pollination effectiveness of the studied bees was not related to floral morph, and that both exotic and native bees showed similar performances on the fruit set of P. carthagenensis.

Seemingly mutualistic relationships can be exploited, in some cases reducing fitness of the exploited species. In plants, the insufficient receipt of pollen limits reproduction. While infrequent pollination commonly underlies pollen limitation (PL), frequent interactions with low-efficiency, exploitative pollinators may also cause PL. In the widespread protandrous herb Campanula americana, visitation by three pollinators explained 63% of the variation in PL among populations spanning the range. Bumblebees and the mediumsized Megachile campanulae enhanced reproductive success, but small solitary bees exacerbated PL. To dissect mechanisms behind these relationships, we scored sex-specific floral visitation, and the contributions of each pollinator to plant fitness using single flower visits. Small bees and M. campanulae overvisited male-phase flowers, but bumblebees frequently visited female-phase flowers. Fewer bumblebee visits were required to saturate seed set compared to other bees. Scaling pollinator efficiency metrics to populations, small bees deplete large amounts of pollen due to highly male-biased flower visitation and infrequent pollen deposition. Thus, small bees reduce plant reproduction by limiting pollen available for transfer by efficient pollinators, and appear to exploit the plant--pollinator mutualism, acting as functional parasites to C. americana. It is therefore unlikely that small bees will compensate for reproductive failure in C. americana when bumblebees are scarce. [ABSTRACT FROM AUTHOR]

Almond (Prunus dulcis (Mill.) D. A. Webb; Rosales: Rosaceae) is a cash crop with an estimated global value of over seven billion U.S. dollars annually and commercial varieties are highly dependent on insect pollination.Therefore, the understanding of basic pollination requirements of the main varieties including pollination efficiency of honey bees (Apis mellifera, Linnaeus, Hymenoptera: Apidae) and wild pollinators is essential for almond production. We first conducted two lab experiments to examine the threshold number of pollen grains needed for successful pollination and to determine if varietal identity or diversity promotes fruit set and weight. Further, we examined stigma and ovules of flowers visited by Apis and non-Apis pollinators in the field to study the proportion of almond to non-almond pollen grains deposited, visitation time per flower visit, and tube set. Results indicate that the threshold for successful fertilization is around 60 pollen grains, but pollen can be from any compatible variety as neither pollen varietal identity nor diversity enhanced fruit set or weight. Andrena cerasifolii Cockerell (Hymenoptera: Andrenidae) was a more effective pollinator on a per single visit basis than Apis and syrphid flies. Nevertheless, Apis was more efficient than A. cerasifolii and syrphid flies as they spent less time on a flower during a single visit. Hence, planting with two compatible varieties and managing for both Apis and non-Apis pollinators is likely to be an optimal strategy for farmers to secure high and stable pollination success. [ABSTRACT FROM AUTHOR]

Many species of the sexually deceptive genus Ophrys are characterized by insect-like flowers. Their form has been traditionally considered to play an important role in pollinator attraction and manipulation. Yet, the evolution of the floral form remains insufficiently understood. We hypothesize that pollinator-mediated selection is essential for driving floral form evolution in Ophrys, but that form components are being subjected to varying selection pressures depending on their role in mediating interactions with pollinators. By using the Eucera-pollinated Ophrys leochroma as a model, our aim has been to assess whether and in what manner pollination effectiveness is altered by experimental manipulation of the flower form. Our results show that floral form plays an essential and, so far, underestimated role in ensuring effective pollination by mechanically guiding pollinators towards the reproductive structures of the flower. Pollinators are significantly less effective in interacting with flowers having forms altered to resemble those of species pollinated by different hymenopteran genera. Further, those components used by pollinators as gripping points were found to be more effective in ensuring pollinia transfer than those with which pollinators do not directly interact. Thus, mechanically active and inactive components appear to be under different selection pressures. As a consequence, mechanically active components of the flower form could reflect adaptations to the interaction with particular pollinator groups, whereas mechanically inactive components can vary more freely. Disentangling selection patterns between the functionally different components of flower form may provide valuable insights into the mechanisms driving the morphological diversification of sexually deceptive pollination systems. [ABSTRACT FROM AUTHOR]

There is a growing consensus that the world is facing a pollination crisis. To mitigate crop pollination deficits, some management strategies include the massive introduction of managed bee species, yet quite often they are applied blindly, as information on crop pollination effectiveness for each single pollinator species of assemblages is usually not available. Therefore, the introduction on managed species is not always the best option to improve crop yields. Here, by using the highly pollinator-dependent alfalfa crop (Medicago sativa L.) as a case study, we propose the use of the effectiveness landscape framework to identify key crop pollinator species. According to this framework, in a mutualistic interaction, each species´ effectiveness is represented by the product of a quantitative component and a qualitative one, these being measures of the outcomes of this interaction. We applied this framework for two managed and four wild bee species that visit alfalfa in fields southwest of Buenos Aires province, Argentina. We dissected the quantity components of the pollinator effectiveness landscape by estimating two quantitative subcomponents: visitation rate and flower tripping rate. Also, we estimate pod set as a qualitative component without dissecting it in subcomponents. Our results showed that the contribution of both components and the resulting pollinator effectiveness varied among pollinator species, indicating a contrasting effectiveness of different bee species on alfalfa pollination. For example, pollinator effectiveness was higher for managed than for wild bees, as consequence of their very high visitation rate, however, wild bee flower tripping rate and pod set were as high as managed ones. In fact, wild bees were more effective in promoting flower tripping than one of the managed bees (A. mellifera). This approach allowed us to assess which effectiveness components and subcomponents make pollinator species more or less effective, thus providing valuable information to identify key species to be enhanced to help in closing yield gaps. We suggest that the application of the effectiveness landscape framework would be useful to develop strategies to improve crop pollination service in pollinator-dependent crop systems. • Identification of key crop pollinator species is essential. • Effectiveness landscape decomposes effectiveness into components and subcomponents. • Effectiveness landscape allows us to assess the effectiveness of each crop pollinator species. • This approach is useful for crop pollination management strategies. [ABSTRACT FROM AUTHOR]

The yield of animal-pollinated crops is threatened by bee declines, but its precise sensitivity is poorly known. We therefore determined the yield dependence of Hokkaido pumpkin in Germany on insect pollination by quantifying: (i) the relationship between pollen receipt and fruit set and (ii) the cumulative pollen deposition of each pollinator group. We found that approximately 2500 pollen grains per flower were needed to maximize fruit set. At the measured rates of flower visitation, we estimated that bumblebees (21 visits/flower lifetime, 864 grains/visit) or honeybees (123 visits, 260 grains) could individually achieve maximum crop yield, whereas halictid bees are ineffective (11 visits, 16 grains). The pollinator fauna was capable of delivering 20 times the necessary amount of pollen. We therefore estimate that pumpkin yield was not pollination-limited in our study region and that it is currently fairly resilient to single declines of honeybees or wild bumblebees.

Floral orientation may affect pollinator attraction and pollination effectiveness, and its influences may differ among pollinator species. We, therefore, hypothesized that, for plant species with a generalized pollination system, changes in floral orientation would affect the composition of pollinators and their relative contribution to pollination. Geranium refractum, an alpine plant with downward floral orientation was used in this study. We created upward-facing flowers by altering the flower angle. We compared the pollinator diversity, pollination effectiveness, and pollinator importance, as well as female reproductive success between flowers with downward- and upward-facing orientation. Results indicated that the upward-facing flowers were visited by a wider spectrum of pollinators (classified into functional groups), with higher pollinator diversity than natural flowers. Moreover, due to influences on visitation number and pollen removal, the pollinator importance exhibited by the main pollinator groups differed between flower types. Compared with natural flowers, the pollination contribution of principal pollinators (i.e., bumblebees) decreased in upward-facing flowers and other infrequent pollinators, such as solitary bees and muscoid flies, removed more pollen. Consequently, stigmatic pollen loads were lower in upward- than in downward-facing flowers. These findings reveal that floral orientation may affect the level of generalization of a pollination system and the relative importance of diverse pollinators. In this species, the natural downward-facing floral orientation may increase pollen transfer by effective pollinators and reduce interference by inferior pollinators. [ABSTRACT FROM AUTHOR]

Plant-pollinator interactions are one of the most important and variable mutualisms having major implications for plant fitness. The present study evaluates the interactions between an endemic milkwort, Polygala vayredae, and its floral visitors by studying the temporal variability, foraging behaviour and effectiveness of floral visitors in three populations during three consecutive years. The flowers were visited by a diverse array of insects, totalling 24 different species. However, only four species were effective pollinators, depositing pollen on stigmas after one visit, while the remaining species behaved as nectar robbers, secondary nectar robbers or nectar thieves and were completely ineffective for pollination. Among the effective pollinators, two groups with distinct foraging behaviours were observed: the nectar collecting long-tongued bees Bombus pascuorum and Anthophora sp. and the pollen collectors Eucera longicornis and Halictus sp. No significant differences were observed among pollinators in their efficiency in pollen deposition on stigmas, but significant differences were observed in the foraging behaviour between nectarivorous and pollen collectors. Variation in the abundance and assemblage of floral visitors was observed at the temporal scale and among populations, with the effective pollinators being generally scarce. Consequently, the reproductive outcome in this species was low and significantly variable among populations and years. The results highlight the importance of studying floral visitor effectiveness when determining pollinator assemblages. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

* Premise of the study: Exceptions to the ideal of complete reproductive isolation between species are commonly encountered in diverse plant, animal, and fungal groups, but often the causative ecological processes are poorly understood. In flowering plants, the outcome of hybridization depends in part on the effectiveness of pollinators in interspecific pollen transport. In the Asclepias exaltata and A. syriaca (Apocynaceae) hybrid zone in Shenandoah National Park, Virginia, extensive introgression has been documented. The objectives of this study were to (1) determine the extent of pollinator overlap among A. exaltata, A. syriaca, and their hybrids and (2) identify the insect taxa responsible for hybridization and introgression. * Methods: We observed focal plants of parental species and hybrids to measure visitation rate, visit duration, and per-visit pollinia removal and deposition, and we calculated pollinator effectiveness and importance. * Key results: Visitation rates varied significantly between the 2 yr of the study. Overall, Apis mellifera , Bombus sp., and Epargyreus clarus were the most important pollinators. However, Bombus sp. was the only visitor that was observed to both remove and insert pollinia for both parent species as well as hybrids. * Conclusions: We conclude that Bombus may be a key agent of hybridization and introgression in these sympatric milkweed populations, and hybrids are neither preferred nor selected against by pollinators. Thus, we have identified a potential mechanism for how hybrids act as bridges to gene flow between A. exaltata and A. syriaca. These results provide insights into the breakdown of prezygotic isolating mechanisms. [ABSTRACT FROM AUTHOR]

Assessing the relative contributions to seed production made by different types of floral visitors is fundamental to understanding the evolution of floral morphology and the influence that particular pollinator taxa have on plant fitness and reproduction. This 3-year study examined the pollinator activity and the seed production in three populations of Lepidium papilliferum, a threatened mustard endemic to sagebrush-steppe habitat in southwest Idaho. Relative amounts of time visitor taxa spent foraging on flowers, visitation rates (number of flowers visited per unit time during a foraging bout), and pollination effectiveness (fruit set per single visit to a virgin flower) were recorded for each of 12 insect taxa that visited L. papilliferum flowers. Relative contributions to seed production were calculated as the product of relative interaction frequencies (the relative number of flowers visited by each taxon-the 'quantity' component of pollination) and pollination effectiveness (fruit set per single visit to a virgin flower-the 'quality' component of pollination). Despite the superiority of some insect taxa in terms of pollination effectiveness, estimates of relative pollinator contributions to seed production were influenced primarily by an insect taxon's interaction frequency with flowers. Pollinator assemblages varied widely both spatially and temporally, which suggest that L. papilliferum is not under strong selective pressure to shift from its generalist pollination strategy toward greater specialization. For this threatened plant, reliance on a diverse assemblage of insect pollinators may serve as an important buffer against disruption in reproductive success caused by fluctuations in population sizes of individual pollinator taxa. [ABSTRACT FROM AUTHOR]

• Premise of the study: Pollination is a critical phase for plant reproduction, but ecological and evolutionary outcomes by pollinators may be counteracted by fl oral herbivores. These interacting assemblages may also be altered (directly or indirectly) by introduced species, especially on oceanic islands. In this study, we analyzed the effects of opportunistic nectar-feeding passerine birds and native (semi-slugs) and introduced (rats) fl oral herbivores on the reproductive success of Canarina canariensis. • Methods: Manual pollination experiments were conducted to determine plant breeding system and pollen limitation. We also identified floral visitors and their visitation frequencies by censuses. Bird pollination effectiveness was evaluated by selective exclosures. The intensity of floral herbivory by native vs. introduced herbivores and its effect on plant fitness was estimated in different areas within the Canary island of Tenerife. • Key results: Canarina canariensis had a very low spontaneous selfing ability and high pollen limitation, despite being selfcompatible. Birds increased fruit set and the percentage of viable seeds per fruit, while florivores, the principal fl oral visitors, reduced them. Semi-slugs mainly consumed male reproductive organs, while rats preferred female. There was a strong withinisland spatial variation in the herbivory intensity. • Conclusions: Opportunistic nectar-feeding birds increase the production of viable seeds in C. canariensis , but their beneficial effects are counteracted by the high incidence of fl oral herbivory. Because native semi-slugs damaged anthers more frequently than did introduced rats, these florivores may differ in their effects on male and female plant reproductive success. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Onion ( Allium cepa L.) is protandrous in nature and requires cross-pollination to avoid inbreeding. The pollination potential of native bees (Hymenoptera) and true flies (Diptera) was assessed in the perspective of finding the best pollinators for onion cross-pollination and seed multiplication. The community of pollinators was composed of four bee species and twelve true fly species. Episyrphus balteatus, Eupeodes sp., Musca domestica and Eristalinus aeneus were the most abundant pollinators. The maximum pollinator activity was observed from 12 to 24 days after opening of the flowers. The pollination effectiveness of tested bees ( Apis dorsata and Apis florea) was greater than true flies ( E. balteatus, Eupeodes sp., M. domestica, E. aeneus and Callihoridae sp.) in terms of Spears values. [ABSTRACT FROM AUTHOR]

Insular floras, characterized by simple pollination networks, sometimes include novel mutualistic agents such as nonspecialist nectarivores. In this study we confirmed the effective pollination of Isoplexis canariensis by opportunistic nectar-feeding birds in Tenerife, Canary Islands, Spain. This plant is among the ornithophilous species of the Canarian flora that lack past and present specialist nectarivorous birds. Experimental hand pollinations revealed self-compatibility, but cross-pollinated flowers produced a greater percentage of viable seeds than self-pollinated ones. Flowers were visited by five species of birds (Phyllloscopus canariensis, Parus caeruleus. Sylvia melanocephala, Serinus canarius, and Fringilla coelebs) and by the endemic lizard (Gallotia galloti, Lacertidae). Insect pollination was absent, and the few insect visitors acted as nectar thieves or secondary nectar robbers. Birds represented 93.1% of total Visits, with the Canarian Chiffchaff, Ph. canariensis, being the most frequent visitor. Flowers visited by birds set more, larger, and heavier fruit than flowers from which birds were excluded. Bird visitation also enhanced seed viability. These results demonstrate the active role of these opportunistic birds as effective pollinators of this Canarian bird-flower species. Further, the results reveal the need to consider the effect of these birds on the evolution of ornithophilous floral traits in absence of specialist nectarivores. [ABSTRACT FROM AUTHOR]

The timing and effectiveness of pollinator visitation to flowers is an Important factor influencing mating patterns and reproductive success. Multiple pollinator probes to a flower may increase both the quantity and genetic diversity of progeny, especially if single probes deposit insufficient pollen for maximal seed set or if the interval between probes is brief. When pollen carryover is limited, sequential pollen loads may also differ markedly in sire representation. We hypothesized that these conditions help explain high levels of multiple paternity in Mimulus ringens fruits. We documented all bee visits to individual flowers, quantified resulting seed set, and determined paternity for 20 seeds per fruit. Most (76%) flowers received multiple probes, and the interval between probes was usually <30 mm. Flowers probed multiple times produced 44% more seeds than flowers probed once. All fruits were multiply sired. Flowers receiving a single probe averaged 3.12 outcross sires per fruit, indicating that single probes deposit pollen from several donors. Multiple paternity was even greater after three or more probes (4.92 outcross sires), demonstrating that sequential visits bring pollen from donors not represented in the initial probe. [ABSTRACT FROM AUTHOR]

Abstract It has been unclear how effective each visitor for pollination is in plants visited by various kinds of animals. This is a topic of recent interest in pollination biology, but quantitative evidence is limited. We have determined whether flowers of Hosta sieboldiana are morphologically specialized for one of the three pollinating bumblebee species, Bombus consobrinus, B. diversus and B. honshuensis , which have significantly different proboscis lengths from each other. We measured the amount of pollen removed from the anthers and the amount of pollen deposited on the stigma at each single visit to the flowers of H. sieboldiana , as measures of pollination effectiveness. We found that the pollination effectiveness did not differ among the three bumblebee species. We also determined which part of a flower or pollinator is related to the pollination effectiveness of each of the three bumblebee species. A floral structure consisting of a protruding pistil and stamens and a tapered broad-tube part may lead to similar pollination effectiveness among the bumblebee species. Flowers of H. sieboldiana are not morphologically specialized for any one of the three bumblebee species. [ABSTRACT FROM AUTHOR]

(1) Background: Cardiocrinum cordatum (Thunb.) Makino (Liliaceae) is a forest perennial herb distributed in East Asia. Although flower visitors for this plant species have been well reported, their contribution to pollination remains unknown. (2) Methods: We evaluated pollination contribution for visitors of C. cordatum flowers in a natural cool temperate forest. We investigated visiting frequency, the number of pollen grains per body surface, fruit set, and the mean number of seeds per fruit produced after a single visit of each visiting species. Combining the results of these experiments, we determined the most important pollinators of this species. (3) Results: For the population investigated in the study, the three most essential pollinators were the bumblebee (Bombus diversus tersatus) (Apidae), sweat bee (Halictidae sp.), and marmalade hoverfly (Episyrphus balteatus) (Syrphidae). Additionally, we found that the contribution of a flower-visiting ant species (Myrmica ruginodis Nylander (s.l.)) (Formicidae) is small. (4) Conclusions: Pollinator contributions differed among flower visitors. Our results underscore the insufficiency of current information about flower-visiting species to evaluate pollination contribution. [ABSTRACT FROM AUTHOR]