Higher Pollinator Research Articles

Biodiversity and Ecosystem Functions Across an Afro-Tropical Forest Biodiversity Hotspot

Ecosystem functions are important for the resilience of ecosystems and for human livelihood quality. Intact habitats and heterogeneous environments are known to provide a large variety of ecosystem functions. Natural and near natural ecosystems surrounding agroecosystems may positively support crop growing conditions and thus facilitate crop yields. In contrast, monocultures of crops and trees as well as degraded landscapes are known to provide less ecosystem functions. The Taita Hills in southern Kenya are part of the Eastern Afromontane biodiversity hotspot, and represent a habitat mosaic consisting of largely intact cloud forests, agroecosystems and plantations of exotic trees. In this region, subsistence farmers rely on ecosystem functions provided by natural ecosystems. In this study, we analyze three proxies of biodiversity and ecosystem functions, namely pollination activity, predation rates, and arthropod diversity in tree canopies. We set study plots along forest-agroecosystem-gradients, covering cloud forest, forest edge and agricultural fields, as well as plantations of exotic trees. We assessed environmental conditions, to evaluate the extent to which local environmental factors influence ecosystem functions. Based on these data we investigate potential spill over of ecosystem functions from forest into adjoining agroecosystems. For predation rates we found trends of spill over effects from forest interior into the agroecosystem. The expression of ecosystem functions differed among habitat types, with comparatively high predation rates in the forest, high pollinator activity in the open agricultural areas, and highest arthropod diversity along the forest edge. Eucalyptus plantations showed reduced ecosystem functions and lowest arthropod diversity. Local factors such as vegetation cover and flower supply positively influence pollinator activity. Our study show that natural ecosystems may positively contribute ecosystem functions such as predation, while the homogenization of biota through planting of invasive exotic tree species significantly reduce biodiversity and ecosystem functions. Transition habitats such as forest margins, and small-scale ecological enhancement positively influences biodiversity and ecosystem functions.

Pollination efficiency and pollen limitation in bistaminate vs tetrastaminate Lamiaceae

AbstractThe evolution of bilabiate flowers in Lamiaceae has several times led to a reduction in stamen number. It is generally assumed that stamen reduction goes along with decreasing pollen production. One should, therefore, expect that bistaminate flowers have either a more efficient pollen transfer mechanism or a higher selfíng rate than tetrastaminate species to adapt to the stamen reduction. We tested this hypothesis in a community of Lamiaceae including three bistaminate and three tetrastaminate species. The results of selfing experiments, extra‐pollination, counting pollen number, and stigmatic pollen load analysis were used to calculate the autonomous selfing index, the pollen limitation index, and the pollination efficiency index. The results indicate a significantly lower pollen number in bistaminate flowers than in tetrastaminate flowers of similar anther size. Bistaminate species shared a higher selfing rate which was related to their structural adaptation to delayed selfing. In Ziziphora clinopodioides, the delayed selfing was accompanied by low pollination efficiency, and plants suffered from pollen limitation at the location studied. However, in Salvia sclarea and Salvia hypoleuca, which benefited from a relatively high pollination efficiency, no pollen limitation was observed. Our results reveal a close association between adaptive mechanisms such as increasing precision of pollen transfer and evolution of delayed selfing with stamen reduction in bistaminate Lamiaceae.

Management‐dependent effects of pollinator functional diversity on apple pollination services: A response–effect trait approach

AbstractFunctional traits mediate the response of communities to disturbances (response traits) and their contribution to ecosystem functions (effect traits). To predict how anthropogenic disturbances influence ecosystem services requires a dual approach including both trait concepts. Here, we used a response–effect trait conceptual framework to understand how local and landscape features affect pollinator functional diversity and pollination services in apple orchards.We worked in 110 apple orchards across four European regions. Orchards differed in management practices. Low‐intensity (LI) orchards were certified organic or followed close‐to‐organic practices. High‐intensity (HI) orchards followed integrated pest management practices. Within each management type, orchards encompassed a range of local (flower diversity, agri‐environmental structures) and landscape features (orchard and pollinator‐friendly habitat cover). We measured pollinator visitation rates and calculated trait composition metrics based on 10 pollinator traits. We used initial fruit set as a measure of pollination service.Some pollinator traits (body size and hairiness) were negatively related to orchard cover and positively affected by pollinator‐friendly habitat cover. Bee functional diversity was lower in HI orchards and decreased with increased landscape orchard cover. Pollination service was not associated with any particular trait but increased with pollinator trait diversity in LI orchards. As a result, LI orchards with high pollinator trait diversity reached levels of pollination service similar to those of HI orchards.Synthesis and applications. Pollinator functional diversity enables pollinator communities to respond to agricultural intensification and to increase pollination function. Our results show that efforts to promote biodiversity provide greater returns in low‐intensity than in high‐intensity orchards. The fact that low‐intensity orchards with high pollinator functional diversity reach levels of pollination services similar to those of high‐intensity orchards provides a compelling argument for the conversion of high‐intensity into low‐intensity farms.

High fruit setting rate without male participation: A case study of obligate apomixis in Rhomboda tokioi (Orchidaceae)

Seed production is the key factor for maintaining plant population renewal and development. Because of pollination limitations and other factors, orchids, especially rewardless ones, generally have low fruit set rates. In Rhomboda tokioi, however, the natural fruit setting rate is very high, more than 90%. Common reasons for such a high natural fruit setting rate include high pollinator efficiency, autonomous selfing, seed formation through apomixis and so on. To test these possibilities, we carried out field observations, morphological examinations, and breeding system experiments. The results showed no migration of pollinia into or out of flowers and suggested that the structure of the floral organs hinder autonomous selfing. Interestingly, the fruit setting rate of this orchid was still higher than 90% when the gynostemium was removed prior to flowering. Additionally, after hand pollination, the pollen tube stopped growing at a late stage and could not enter the ovule, indicating the seeds were produced by obligate apomixis. Morphological experiments showed that a megasporocyte first forms a chain tetrad and then develops into a mature embryo sac, while the embryo of the offspring developed from unfertilized egg cells. More interestingly, the offspring had the same number of chromosomes as the female parent. According to the existing theory of apomixis, we can infer that the reproductive model of R. tokioi is Allium-type apomixis.

Overlooked jewels: Existing habitat patches complement sown flower strips to conserve pollinators

Flower strips are a frequently adopted measure to conserve insects, especially pollinators, and are subsidized as Agri-Environmental Scheme in many regions. They provide a high quantity of flowers, but their flower species composition and phenological development is mostly uniform. This may result in only a fraction of pollinator species being enhanced. Flower-rich semi-natural habitat patches along slopes, fences or ditches, may provide resources for additional species, but they are not politically promoted. In this study, we compare pollinator communities in sown perennial flower strips with existing flower-rich herbaceous semi-natural habitat patches, both located at the edge of conventional apple orchards in Southern Germany. The flower strips attracted a higher pollinator abundance and species richness than the existing habitat patches. However, the bee species composition differed between the two habitat types. The existing habitat patches attracted bee species with different pollen specialization than the sown flower strips. Pollinator abundance and species richness varied between the different existing habitat patches indicating a high heterogeneity of these existing habitats, whereas the flower strips showed consistently high pollinator abundance and richness. We conclude that existing herbaceous habitat patches are attractive for pollinators and should be promoted by policy actions. Flower-rich semi-natural habitat patches develop without sowing next to typical agricultural landscape elements like slopes, fences and ditches with moderate mowing or herbicide application. They generally do not compete with agricultural land use and thus have a high potential to promote pollinator conservation.

Pollination Potential of Riparian Hardwood Forests—A Multifaceted Field-Based Assessment in the Vistula Valley, Poland

Riparian forests with oaks, ashes and elms, now highly fragmented and rare in Europe, are considered hotspots for ecosystem services. However, their capacity to provide pollination seems to be quite low, although reports from in-situ research supporting this view are scarce. Our goal was therefore to thoroughly assess their pollination potential based on multifaceted field measurements. For this, we selected six test sites with well-developed riparian hardwood forests, located in the agricultural landscape along the middle Vistula River in Poland. We used seven indicators relating to habitat suitability (nesting sites and floral resources) and pollinator abundance (bumblebees and other Apoidea) and propose a threshold value (AdjMax) based on value distribution and Hampel’s test to indicate the level of pollination potential for this type of riparian forest. The obtained AdjMax for bumblebee density was 500 ind. ha−1, for Apoidea abundance—0.42 ind. day−1, while for nectar resources—200 kg ha−1. We demonstrate that the investigated small patches of the riparian hardwood forest have a higher pollination potential than reported earlier for riparian and other broadleaved temperate forests, but the indicators were inconsistent. As forest islands in the agricultural landscape, riparian hardwood forests play an important role in maintaining the diversity and abundance of wild pollinators, especially in early spring when there is still no food base available elsewhere.

Spatiotemporal Variation in Pollination Deficits in an Insect-Pollinated Dioecious Crop.

Inadequate quantity and quality of pollen reaching the stigmas decreases the sexual reproductive output of plants, compromising yield. Still, the current extent of pollen limitation affecting yield (i.e., pollination deficits) is poorly quantified. This study is aimed at quantifying pollination deficits in kiwifruit orchards, a dioecious plant with a fruit caliber and market value largely dependent on pollination services. For that, we set up a pollination experiment and quantified services and yield provided by current pollination vectors, and under optimal pollination, over two years in a total of twenty-three orchards covering the kiwifruit production range in Portugal. We characterized nine fruit traits and used: (1) fruit weight to calculate pollination deficits and relate them with pollinator diversity and abundance, and environmental variables; and (2) production values, fruit caliber, and market values to calculate economic impact of pollination deficits. Results showed that pollination deficits were variable in time and space and were significantly and negatively correlated with pollinator abundance, while the opposite pattern was obtained for production, supporting the notion that a higher pollinator’s abundance is related to lower pollination deficits and higher yields. Understanding the factors affecting pollination deficits is crucial to depict the need for nature-based solutions promoting pollinators and to resort to management practices assisting pollination.

Rising trend in p​ediatric eosinophilic esophagitis incidence in Spain: Results of a prospective study 2014-16.

The rate of eosinophilic esophagitis (EoE) diagnosis is increasing. This study aims to determine the incidence of EoE in the pediatric population residing in the southwestern Madrid and to analyze whether absolute monthly pollen counts, modified or not by the principal atmospheric pollutants, are associated with it. A cross-sectional study on prospectively recruited patients was designed to calculate the incidence of EoE in children aged under 15years who were diagnosed between September 2014 and August 2016 in twelve hospitals. We collected demographic and symptoms data, date of onset of symptoms, date of medical consultation, and date of endoscopic diagnosis of each included patient. Relative risk estimation was performed to assess the association between the incidence of diagnosis and monthly pollen counts and levels of atmospheric pollutants. All these models were adjusted for the number of total patients that underwent endoscopy at first time. One hundred forty-eight patients were included. The most frequent symptoms were abdominal pain [42.57%], dysphagia [42.57%], and impaction [39%-86%]. The median overall monthly incidence was 1.13 [interquartile rank: 0.97-1.43] cases/100,000 children, and the annual mean was 15.2. The overall analysis of the relationship between incidence and absolute monthly counts, corrected for the number of first-time endoscopies performed, revealed no statistically significant association with pollen and air pollutants. There was a higher frequency of diagnosis during the pollination period of Cupressaceae [relative risk 1.647; 95% CI (1.192-2.276) p<.002] and during February and November (relative risk 1.67; p<.01). This study confirms the high incidence of eosinophilic esophagitis and also suggests a period of higher incidence of diagnosis in the months of February and November as well as in the period of high pollination of Cupressaceae.

Seed Set Patterns in East African Highland Cooking Bananas Show Asymmetric Distribution in Bunches and Fruits

Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African Highland Cooking bananas (EAHBs) to inform future decisions on a more targeted approach of increasing seed set and subsequently banana-breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are genetically distinct but belong to the same genetic complex, referred to as EAHBs. Seed set patterns in “Enzirabahima” (AAA), “Mshale” (AA), and “Nshonowa” (AA), all with residual fertility, were examined after hand pollination with a highly male fertile wild banana “Calcutta 4” (AA). Seed set in “Enzirabahima” is predominant in distal hands. Mchare cultivars have a slightly more even distribution of seeds in their hands compared to “Enzirabahima”. There is a gradual increase in seed set from proximal to distal hands with a slight drop in the last hand. This pattern is more definite in “Enzirabahima” and “Mshale”, while “Nshonowa” has a somewhat inconsistent pattern. There is also a drop in seed set per 100 fruits per hand from small to larger bunches. However, larger bunches have a higher pollination success compared to smaller bunches. They therefore set more seed on 100 fruits per hand and per bunch basis, if bunches without seed are accounted for. Pollination success rate increases from smaller to larger bunches of EAHBs. Seed set is biased toward the distal third part of fruits of examined EAHBs, as well as tetraploid Matooke hybrid “401K-1” (AAAA), and improved diploid “Zebrina” GF (AA) that were used for comparison. In comparison, in the highly female fertile “Calcutta 4”, seed set is along the entire length of the fruit. Seed set bias in the distal hands and distal end of fruits suggests a systematic mechanism rather than a random occurrence. It is expected that this information will provide a foundation for increased crossbreeding efficiency in bananas.

Using the Lonsdorf model for estimating habitat loss and fragmentation effects on pollination service

One of the most important issues related to landscape ecology and ecosystem services is finding the pattern of habitat patches that offers the highest pollination in agricultural landscapes. In this regard, two processes of habitat loss and fragmentation strongly affect the relationship between pollination and the pattern of habitat patches. In the present study, we aimed to examine the effects of habitat loss and fragmentation on pollination separately. For this purpose, first, we generated different simulated agricultural landscapes, including two habitats of forest and agriculture. Then, according to the Lonsdorf model, we estimated the potential of the simulated landscapes in providing pollination in different scenarios. Finally, using statistical models, we estimated the effects of habitat loss and fragmentation on pollination at the landscape and farm levels. Our results showed that the effects of habitat loss and fragmentation on pollination were completely different at the landscape and farm levels. At the landscape level, fragmentation negatively affected pollination, but at the farm level, the maximum pollination rate was observed in the landscapes with a high degree of fragmentation. Regarding the habitat loss effects, our results showed that pollination decreased linearly at the landscape level as habitat amount decreased, but at the farm level, it decreased exponentially. The present study considered the level of analysis (i.e., landscape and farm levels) as a critical factor affecting pollination changes caused by fragmentation. We showed that using the Lonsdorf model could lead to confusing results for the landscape ecologists and alert farmers who want to reduce the adverse effects of fragmentation on their products by creating new forest patches. Therefore, agriculturalists and landscape ecologists should consider that the pollination rate at the landscape and farm levels is completely different according to the model and provide contradictory results about the process of habitat loss effects on pollination.

Agricultural management and local knowledge: key factors for the conservation of socio-ecosystems in the face of the pollinator world crisis

Background: Pollinators are key for the survival of a great percentage of angiosperm species and 75 % of production from cultivated species is expected to decrease in the absence of pollinators.&#x0D; Questions: The goal of this study is to understand the role of agricultural management and local knowledge on pollination for the conservation of different insect species in communities where there is no direct tradition of pollinator management.&#x0D; Study site: The study was conducted in central Mexico in a community with a traditional agroforestry system of semi-terraces called metepantle .&#x0D; Methods: To estimate pollinator richness, we collected insects from the order Hymenoptera and Diptera as well as plants that were flowering on the borders of the metepantle . To evaluate local knowledge on pollination and its relation to agricultural management we performed semi-structured interviews.&#x0D; Results: We found high pollinator richness for a temperate region. However, knowledge of biological pollination was scarce probably because the predominant crops are wind pollinated. Local knowledge on pollination and pollinators is not very extensive and varied in relation to the management of their metepantle and socioeconomic factors that influence the individual knowledge of people.&#x0D; Conclusions: The structural and management characteristics of the traditional agricultural metepantle system promote holistic management that favors diversity and productivity of the agroforestry system while promoting local pollinator conservation.

Effect of floral traits mediated by plant-soil feedback on the relationship between plant density and fecundity: Case study of Tamarix chinensis in the Yellow River Delta, China

Density-dependent fecundity is important for the successful recruitment and reproduction of plant populations, especially for plants inhabiting saltmarshes with highly varied environmental gradients. The highest fecundity of plants at intermediate densities is usually correlated with high pollinator visitation rates mediated by floral displays of medium density. However, little data explains the mechanism that floral traits and pollinator visitation optimize at intermediate densities. Here, we investigated how the density of Tamarix chinensis (in the Yellow River Delta) influence soil conditions, floral traits, pollinator visitation rates, and plant fecundity in environments with different soil salinity and moisture. At all sites, soil moisture and floral traits (number and length of racemes, amounts of floral volatiles) increased parabolically with increasing density, whereas soil salinity declined. Soil conditions and floral traits of T. chinensis were optimal at intermediate plant densities, which, in turn, maximized pollinator visitation and seed set. Reduced fecundity at plant densities that were higher than optimal was related with higher soil salinity, shorter raceme length, and lower amounts of floral volatiles in T. chinensis. Regular freshwater restoration showed a positive impact on pollinator visitation and fecundity of T. chinensis. Consequently, positive plant-soil feedback enhanced floral traits and pollinator visitation, which are related with the optimal fecundity of T. chinensis at intermediate densities. Thus, the density of T. chinensis should be managed in restoration projects of the T. chinensis population through artificial transplantation. The transplanting density of T. chinensis should be strictly controlled in harsh environment, while this requirement could be relaxed in mild conditions.

The Sterile Appendix Underpins High Pollinator Specificity in Arisaema with a Lethal Kettle Trap Pollination System

Photo 1: The uniquely shaped Arisaema inflorescences (A. angustatum [left] and A. peninsulae [right]) that are reminiscent of carnivorous pitcher plants. However, unlike pitcher plants that absorb nutrients from captured insects, Arisaema inflorescences trap insects for successful pollination. Photo credit: Takayuki Shimizu. Photo 2: Fungus gnats trapped within female inflorescences of Arisaema angustatum and A. peninsulae showcasing the marked difference in pollinator composition. Brevicornu sp.1 (left) trapped by A. peninsulae and Cordyla murina (right) trapped by A. angustatum. Bar = 1 mm. Photo credit: Rikuo Sato. Photo 3: The upper part of an Arisaema inflorescence (A. angustatum [left] and A. peninsulae [right]). When we removed the sterile appendix (indicated by the arrow), the number of visitations by principal pollinators significantly decreased. Our results indicate that the appendix underlies high pollinator specificity in Arisaema. Photo credit: Takayuki Shimizu. These photographs illustrate the article “The sterile appendix of two sympatric Arisaema species lures each specific pollinator into deadly trap flowers” by Kenji Suetsugu, Rikuo Sato, Satoshi Kakishima, Yudai Okuyama, and Masahiro Sueyoshi published in Ecology. https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.3242

Competition for pollination and isolation from mates differentially impact four stages of pollination in a model grassland perennial

Abstract Species that persist in small populations isolated by habitat destruction may experience reproductive failure. Self‐incompatible plants face dual threats of mate‐limitation and competition with co‐flowering plants for pollination services. Such competition may lower pollinator visitation, increase heterospecific pollen transfer and reduce the likelihood that a visit results in successful pollination. To understand how isolation from mates and competition with co‐flowering species contribute to reproductive failure in fragmented habitat, we conducted an observational study of a tallgrass prairie perennial Echinacea angustifolia. We quantified the isolation of focal individuals from mates, characterized species richness and counted inflorescences within 1 m radius, observed pollinator visitation, collected pollinators, quantified pollen loads on pollinators and on Echinacea stigmas, and measured pollination success. Throughout the season, we sampled 223 focal plants across 10 remnant prairie sites. We present evidence that both co‐flowering species and isolation from mates substantially limit reproduction in Echinacea. As the flowering season progressed, the probability of pollinator visitation to focal plants decreased and evidence for pollen‐limited reproduction increased. Pollinators were most likely to visit Echinacea plants from low‐richness floral neighbourhoods with close potential mates, or plants from high‐richness neighbourhoods with distant potential mates. Frequent visitation only increased pollination success in the former case, likely because Echinacea in high‐richness floral neighbourhoods received low‐quality visits. Synthesis. In Echinacea, reproduction was limited by isolation from potential mates and the richness of co‐flowering species. These aspects of the floral neighbourhood influenced pollinator visitation and pollination success, although conditions that predicted high visitation did not always lead to high pollination success. These results reveal how habitat modification and destruction, which influence floral neighbourhood and isolation from conspecific mates, can differentially affect various stages of reproductive biology in self‐incompatible plants. Our results suggest that prairie conservation and restoration efforts that promote patches of greater floral diversity may improve reproductive outcomes in fragmented habitats.

Seasonal change of flower sex ratio and pollinator dynamics in three reproductive ecotypes of protandrous plant

AbstractCimicifuga simplex has three genetically and ecologically distinct pollination morphs with different flowering phenology, flower sex expressions, and selfing rates. A previous study showed that strong protandry in hermaphroditic flowers of C. simplex causes there to be seasonal minority sexes; for example, unisexual female ramets are advantageous in the first half of the flowering season and bloom then (minority sex hypothesis). That study, however, did not distinguish among the three pollination morphs of C. simplex. We investigated seasonal sex ratio changes and pollinator environments of the three morphs to verify and expand the minority sex hypothesis. We investigated flowering phenology, pollinator quantity and quality, seasonal population sex ratio dynamics, and stamen/ovule ratios in hermaphroditic flowers. We also examined the seasonal female reproductive success of hermaphroditic flowers, and the effect of male flower excision on fruit set by morph II hermaphroditic flowers. Morph I (mainly hermaphroditic and female ramets) had high pollinator quality and quantity. Fruit set of hermaphroditic ramets was high throughout the flowering season. Morph II (hermaphroditic and andromonoecious ramets) had low pollinator quality, and few pollinators visited near the beginning and end of the season. Removal of male flowers led to a pollen limitation. Morph III (hermaphroditic ramets and a high selfing rate) had very low pollinator abundance throughout the flowering season, and male and female phases largely overlapped. The scarcity of male flowers in morph I is likely a result of the high pollinator quantity and quality. The high fruit set suggests that no pollen limitation existed. The low pollinator quality and quantity of the morph II population caused it to suffer from pollen limitation and may explain the absence of unisexual female ramets in this morph. The high selfing rate of morph III may be due to the extremely low pollinator abundance. Theoretical studies have indicated that the optimal investment allocation to male and female functions depends on whether a pollen limitation exists. In C. simplex, the observed relationships between pollinator environment and reproductive systems are consistent with these theoretical models.

Insect pollinator dependence of shea (Vitellaria paradoxa C.F. Gaertn.) in the Guinea Savanna zone of Ghana

Shea (Vitellaria paradoxa C.F. Gaertn.) is a multipurpose tree species indigenous to the Sudano Sahelian zone of Africa and occurs as the most abundant economic tree species in northern Ghana. The edible oil (shea butter) extracted from shea kernel is ranked as the most economic product of the species. Although fruit set and yield of shea are known to be influenced by insect pollination, the actual contribution of insect pollinators to its reproductive success has rarely been studied. This study estimated the percentage insect pollinator dependence and monetary value of insect pollination per bag of shea kernel (85 kg) in the Guinea savanna zone. Open pollination and insect exclusion treatments were applied to the flowers of 18 randomly selected matured shea trees and observed from the onset of flowering to fruit maturity. Proportion of total production value attributed to insect pollination approach was used in estimating the monetary value of pollination per bag of shea kernel with the average market price as proxy. The study revealed an insect pollinator dependence of 77% and 73% for fruit set and dry kernel yield, respectively. Mean number of fruit set per inflorescence varied significantly between insect-excluded and open-pollinated inflorescences (p < 0.05). The monetary value of insect pollination was estimated at GH₵ 73.21 (US$ 18.67) per bag of kernel as of August 2016. Shea is a high insect pollinator–dependent species and the conservation of insect pollinators would be critical to the sustainability of yield.

Effective pollination of Aeschynanthus acuminatus (Gesneriaceae) by generalist passerines, in sunbird-absent East Asia

Aeschynanthus (Gesneriaceae), a genus comprising approximately 160 species in subtropical Southeast Asia, has red, tubular flowers, typical of a sunbird pollination syndrome. A. acuminatus, the species that is distributed extending to the northern edge of the genus, where the specialized nectarivorous sunbirds are absent, possesses reddish-green flowers and a wide-open corolla tube, flowering time shifts from summer to winter and the species achieves high fruiting success. This atypical flower led us to investigate the pollination biology of this species. Three species of generalist passerines, Grey-cheeked Fulvetta (Alcippe morrisonia, Sylviidae), White-eared Sibia (Heterophasia auricularis, Leiothrichidae) and Taiwan Yuhina (Yuhina brunneiceps, Zosteropidae), were recorded visiting A. acuminatus flowers. Pollination effectiveness was quantified via conspecific pollen presence on stigmas and natural fruit set. The significantly high natural fruit set (60%) and conspecific pollen transfer rate (94%) indicate high reproductive success facilitated by the accurate pollen placement on the birds. The existence of copious (61 µL) and highly diluted (7%) hexose-dominant nectar, together with a major reflectance peak of corolla lobe in the long-wavelength red color spectrum, is consistent with the pollination syndrome of generalist passerines. The high pollination effectiveness of A. acuminatus due to the recruitment of generalist passerines as pollinators, and the specializations of floral traits to match generalist bird pollination, appear crucial in the successful colonization on islands such as Taiwan that lack specialized bird pollinators.

Pollination efficiency and foraging behaviour of honey bees and non‐Apis bees to sweet cherry

Abstract Crop pollination generally increases with pollinator diversity and wild pollinator visitation. To optimize crop pollination, it is necessary to investigate the pollination contribution of different pollinator species. In the present study, we examined this contribution of honey bees and non‐Apis bees (bumble bees, mason bees and other solitary bees) in sweet cherry. We assessed the pollination efficiency (fruit set of flowers receiving only one visit) and foraging behaviour (flower visitation rate, probability of tree change, probability of row change and contact with the stigma) of honey bees and different types of non‐Apis bees. Single visit pollination efficiency on sweet cherry was higher for both mason bees and solitary bees compared with bumble bees and honey bees. The different measures of foraging behaviour were variable among non‐Apis bees and honey bees. Adding to their high single visit efficiency, mason bees also visited significantly more flower per minute, and they had a high probability of tree change and a high probability to contact the stigma. The results of the present study highlight the higher pollination performance of solitary bees and especially mason bees compared with bumble bees and honey bees. Management to support species with high pollination efficiency and effective foraging behaviour will promote crop pollination.

On the low reproductive success of two Cyrtopodium species (Orchidaceae: Cyrtopodiinae): The relative roles of biotic and abiotic pollination

AbstractRewardless orchid species are pollinated by deception and have reduced reproductive success. Those species that present self‐compatibility followed by alternative mechanisms of autogamy may compensate for such episodic allogamy events. This is the case for rain‐assisted self‐pollination, a rare mechanism in Orchidaceae. In this study, we investigated the reproductive biology of two terrestrial species: Cyrtopodium hatschbachii and C. paludicolum. We studied their reproductive systems, examined pollinators and male and female successes, and ascertained if rain promotes self‐pollination. Both species are allogamous but self‐compatible. However, natural fruit set is low, not exceeding 1.40% during 4 years of observation. This may result from the reduced frequency of pollinator visitation followed by a high pollinator specificity, because each species was pollinated by a single specialist bee. Although spontaneous selfing did not occur, we verified fruits formed by rain action. The evaporation of the water droplet that accumulates on stigma helps the pollinarium to slip back, promoting selfing. This occurred in approximately 10% of C. hatschbachii fruits, but in C. paludicolum it was recorded only once during three observation years. This indicates that the phenomenon happens at random and may vary temporally. Nevertheless, rain may confer additional fruit set, especially under circumstances of pollinator limitation. Overall, we confirmed deception as a strategy for this understudied genus. In addition, we report a further two cases of rain‐assisted self‐pollination for Cyrtopodium, for species from the center of diversity of the genus, indicating that it may be more widespread than previously thought.

Landscape heterogeneity increases the spatial stability of pollination services to almond trees through the stability of pollinator visits

High pollinator reliability is essential to maintain a stable and predictable crop production. However, still few studies have considered landscape effects on the stability (low variability) of the pollination service to crops. The stability of pollination services may increase in heterogeneous landscapes with high availability and diversity of alternative habitats. By using data on pollinator visitation and fruit production in 18 almond tree fields in Mallorca Island, we related landscape heterogeneity (richness, evenness and diversity of land-cover classes) at 1 and 2 km-radius buffer zone to the spatial (among-tree) stability of their pollination services (total visit rates, wild pollinators’ visit rates, pollinator richness and fruit set). Overall, landscape heterogeneity increased the spatial stability (i.e., decreased spatial variability) of pollination services to almond trees. Interestingly different components of heterogeneity influenced diverse components of this service. Thus, increasing landscape evenness at the 2 km buffer zone increased the spatial stability of both total pollinator visitation and fruit set. However, the stability of wild-pollinators’ visit rate as well as the stability of pollinator richness increased instead with the percentage of natural habitat in the buffers, as the abundance of wild pollinators might depend on the total availability of habitat in the field surroundings. The stability in pollinator richness had a further positive effect on the stability of fruit set, indicating the importance of diversity maintaining stable crop production. Lastly, fruit set was also negatively affected by landscape richness, probably because of a loss of pollinator source habitat when the number of land uses is too high. Preserving a heterogeneous habitat of high quality in the surroundings of crop fields may help to maintain a stable fruit production.