Effective Pollinators Research Articles

The effective pollination period of the olive cultivar ‘Arbequina’ (Olea europaea L.) in a non-traditional production region

• ‘Arbequina’ is self-incompatible and fully compatible with ‘Coratina’. • The EPP was estimated to be at least seven days by different methodologies. • The EPP is not a limiting factor for ‘Arbequina’ in Uruguay. In non-traditional production regions, olive cultivation is facing challenges sometimes associated with poor fruit set. That is the case of Uruguay, where olive cultivation has reached 7000-planted hectares; however, yields are low and irregular. Uruguay has a temperate climate with particular characteristics that differentiate it from the Mediterranean basin. It presents greater annual rainfall, reaching up to 1600 mm, high relative humidity and high interannual variability in the rainfall and thermal regime. We hypothesized that these environmental conditions may affect the reproductive biology of olive trees, reduce their Effective Pollination Period (EPP) and limit fruit set. For this reason, we determined the EPP for ‘Arbequina’, the main olive cultivar in Uruguay, by two methodologies: sequential pollination of flowers of different ages, and analysis of its components (stigmatic receptivity, ovule viability, and pollen tube growth). We determined the EPP to be of at least 7 days with both methods. Stigmatic receptivity, assessed by the ability to support pollen adhesion and germination, was maintained for at least 20 days after anthesis. More than 50% of the evaluated flowers maintained at least one viable ovule 23 days after anthesis, and pollen tubes required between two and three days to reach an ovule. No differences in pollen tube growth were found in relation to the age of the pistil. Our results indicate that a short EPP is not behind the low yields of ‘Arbequina’ in Uruguay.

Herbivory, plant traits and nectar chemistry interact to affect the community of insect visitors and pollination in common milkweed, Asclepias syriaca.

Herbivory can alter plant fitness directly through changing reproductive allocation and indirectly through changing pollinator identity or behavior. Common milkweed is a plant of conservation concern with an inducible chemical defense that is also an important nectar resource. In this study, we aim to understand how herbivory severity and plant traits, including morphology and nectar chemistry, interact to affect insect visitation and pod production in common milkweed. We conducted pollinator watches on plants with experimentally varied herbivory severity and quantified insect frequency and visit length as a response to nectar chemistry, ramet height, number of inflorescences, number of flowers per inflorescence and percent tissue removed. We also quantified pollinator effectiveness and importance. Increased herbivory severity reduced floral displays, including fewer inflorescences and fewer flowers per inflorescence. A reduced floral display was correlated with reduced sucrose, fructose and glucose and resulted in a reduced number and species richness of insect visitors. Fewer flowers per inflorescence reduced the frequency of bumble bee and fly visitors, which were two important pollinators. Although honeybees, flies, small bees, soldier beetles and bumble bees were equally effective pollinators, only bumble bee frequency was positively correlated with pod production. The differences in pollinator visitation have the potential to create diversifying selection on plant floral traits, many of which are also affected by herbivores. This research demonstrates potentially conflicting selection pressures between native and non-native pollinators as well as non-native herbivores.

Epidendrum claustralis (Orchidaceae), another new species from the high Andean forests of the Rupestre group

Epidendrum claustralis, a new species of the Rupestre Group is described and illustrated. It is a novelty from the Departments of Junín, San Martín and Amazonas, Peru. It is compared to the most similar species, Epidendrum excelsum. The species is characterized by the entire lip and with two prominent parallel calli that lean towards each other after pollination or the loss of the pollinarium, closing the entrance of the nectary, and thus avoiding another pollination event.

Impact of Bee and Fly Pollination on Physical and Biochemical Properties of Strawberry Fruit

Improvement in physical and biochemical properties of fruits through cross-pollination is a highly variable phenomenon. It mainly depends on the species of the pollinator and the nature of the crop being pollinated. It is therefore imperative to quantify the relative pollination effectiveness of an insect species for a certain crop species. In the present study, pollination effectiveness of two native bees (i.e., Apis dorsata and A. florea) and two syrphid flies (i.e., Eristalinus aeneus and Eupeodes corollae) were evaluated in terms of physical properties of strawberry fruits at Multan, Pakistan. The physical parameters of resultant fruits included length, pole, equator, fruit set ratio, number of days to reach market maturity, and shelf life. The biochemical properties of fruits resulted from open-pollinated plants (free insect visits) and caged plants (no insect visits) were also compared. The biochemical parameters included TSS (total soluble solids), TA (titratable acidity), vitamin C, and pH. Apis dorsata was the most abundant pollinator, followed by E. aeneus and E. corollae. Based on single-visit effectiveness, A. dorsata proved to be the most effective pollinator, in terms of physical properties, of strawberry fruit. Eristalinus aeneus outcrossed A. florea in terms of fruit set (%). The open-pollinated plants showed better physical and biochemical properties (26% higher TSS, 34% higher TA, but 25% lower pH value) in terms of fruits than the caged plants. Conservation of A. dorsata and E. aeneus can enhance physical and biochemical properties of strawberry fruits in the region.

Reproductive aspects and pollination biology in endoparasiticPilostyles thurberi(Apodanthaceae)

AbstractBiotic pollination is typically a mutualism between plants and their pollinators, where each partner receives a benefit. However, plants can resort to various reproductive strategies to attract pollinators. Within angiosperms, a group of plants known as endoparasites is comprised of only flowers or inflorescences. These plants exhibit various reproductive strategies, such as different sexual systems and attractants, and most are dependent on animals for pollination. In the endoparasitic plants of the family Apodanthaceae, unisexual flowers are predominant, resulting in dependence on pollinators.Pilostyles thurberiis characterized by small flowers, but limited information exists about its reproductive strategies. This study investigated various reproductive aspects ofP. thurberi. We described and compared its hosts, sexual flower arrangement, floral concentration, rewards, and reproductive success in different populations. Furthermore, we determined whether the floral display operates as an attractant by monitoring pollinators for two years. Our results revealed thatP. thurberihas unisexual flowers with male, female, and mixed sex arrangements. Bees and wasps are the effective pollinators and are attracted by the floral display independently of flower sex. This study was the first to record the production of small amounts of crystallized nectar by the nectary disk of both floral sexes. Moreover, the findings were compared with those of other endoparasitic plants, such as Cytinaceae, Mitrastemonaceae, Rafflesiaceae, and other Apodanthaceae. It is necessary to continue studying the plant–pollinator interactions and reproductive strategies of parasitic plants such as Apodanthaceae, since not much evidence on how they reproduce and survive in the wild exists.

Floral scent emission is the highest at the second night of anthesis in Lonicera japonica (Caprifoliaceae)

AbstractFloral color change in diverse plants has been thought to be a visual signal reflecting changes in floral rewards, promoting pollinator foraging efficiency as well as plant reproductive success. It remains unclear whether olfactory signals co‐vary with floral color change. We investigated the production rhythms of floral scent and nectar associated with floral color change in Lonicera japonica. The flowers generally last 2–3 days. They are white on opening at night (N1) and become light yellow the following day (D1), yellow on the second night (N2), and golden on the second day of flowering (D2). Our measurements in the four stages indicated that nectar production decreased significantly from N1 and D1 to N2 and D2, tracking the floral color change. A total of 34 compounds were detected in floral scent and total scent emission was significantly higher in N2 than in the other three stages. The scent emission of three major compounds, Linalool, cis‐3‐Hexenyl tiglate, and Germacrene D was also significantly higher in N2, but the relative content of Linalool decreased gradually, cis‐3‐Hexenyl tiglate increased gradually, and the relative content of Germacrene D did not differ among the four measured stages. Greater scent emission by night than by day suggested a strong olfactory signal to attract nocturnal hawkmoths, the effective pollinators. However, floral scent rhythms in the four stages did not match the color change and nectar secretion, suggesting that floral color (visual) and scent (olfactory) in this species may play different roles in attracting or filtering various visitors.

Scented at day and night: diel variation in the floral scent chemistry of the threatened tree Amburana cearensis (Leguminosae) and effects of this variation on its pollinators

The reproductive success of most angiosperms depends on pollinators. A combination of floral traits, including olfactory cues, are involved in attracting these animals. The emission and chemical composition of floral volatile organic compounds (VOCs) is often associated with the sensory preferences of the most frequent floral visitors. However, the relationship between VOCs and nocturnal and diurnal pollinators is poorly known in tropical dry forests. Our study describes the dynamics of floral scent chemistry throughout the anthesis of Amburana cearensis (Leguminosae) and its association with floral visitors in the Caatinga dry forest, one of the largest expanses of seasonally dry tropical forest (SDTF) in the world. The species is a threatened tree with high socioeconomic importance in the Caatinga and other SDTFs of South America (exploited for timber and medicinal uses). Its flowers emit an intense, pleasant and sweet fragrance throughout anthesis, starting at ∼16:00 h and ending at ∼15:00 h of the following day (lasting 23 h). We used dynamic headspace sampling and gas chromatography coupled with mass spectrometry (GC-MS) to collect and analyze the floral scent within a natural population. The fragrance of A. cearensis was characterized by the dominant presence of monoterpenes, especially linalool and (Z)-linalool oxide (furanoid) and (Z)-linalool oxide (pyranoid), as well as (E,E)-α-farnesene and an aromatic benzenoid, benzyl alcohol. The relative proportions of floral VOCs emitted by A. cearensis changed during anthesis, with a marked presence of linalool in daytime samples (day: 45% / night: 27%) and furanoid (Z)-linalool oxide at night (day: 12% / night: 29%). The dominance of benzyl alcohol, linalool and its oxides in the floral scent of A. cearensis is possibly related to the attraction of nocturnal and diurnal Lepidoptera as pollen vectors. Indeed, we observed six species of butterflies and seven species of moths pollinating the flowers of A. cearensis in 41 h of observations. However, other terpenoids in the fragrant blend possibly contribute to the attraction of additional diurnal floral visitors, including bees, which are also effective pollinators. The continuous scent production throughout anthesis, and the changes in floral scent with a peak of linalool production during the day, may be related to the wide spectrum of pollinators of A. cearensis. This association between floral visitors and dynamics of VOCs presentation may therefore increase the reproductive success of the species, which only blooms every two years and is strictly self-incompatible.

Effect of grazing disturbance on floral display, pollen limitation and plant pollination efficiency in the desert steppe

BackgroundGrazing disturbance usually affects floral display and pollination efficiency in the desert steppe, which may cause pollen limitation in insect-pollinated plants. Effective pollination is essential for the reproductive success of insect-pollinated plants and insufficient pollen transfer may result in pollen limitation. Caragana microphylla Lam is an arid region shrub with ecological importance. Few studies have been conducted on how grazing disturbance influences pollen limitation and pollination efficiency of C. microphylla. Here, we quantify the effect of different grazing intensities on floral display, pollinator visitation frequency and seed production in the Urat desert steppe.ResultsIn C. microphylla, supplemental hand pollination increased the seed set, and pollen limitation was the predominant limiting factor. As the heavy grazing significantly reduced the seed set in plants that underwent open-pollination, but there was no significant difference in the seed set between plants in the control plots and plants in the moderate grazing plots. Furthermore, there was a higher pollinator visitation frequency in plants in the control plots than in plants in the heavy grazing plots.ConclusionsWe found that pollinator visitation frequency was significantly associated with the number of open flowers. Our findings also demonstrated that seed production is associated with pollinator visitation frequency, as indicated by increased seed production in flowers with higher pollinator visitation frequency. Therefore, this study provides insight into the effect of different grazing intensities on floral display that are important for influencing pollinator visitation frequency and pollination efficiency in desert steppes.

Pollination system and reproductive failure in an endangered semi-evergreen tree, Syzygium myhendrae (Bedd. ex Brandis) Gamble

• The relationship between the phenology of Syzygium myhendrae and climatic factors was studied. • Visitation frequency and visitor activity index were calculated for each floral visitor to confirm its pollination efficiency. • The flowers were exclusively visited by honeybees, rockbee, wasps, psyllids and beetles. • Eulophid and pteromalid parasitic wasps were limited the fruit set rate and induced premature fruit drop. • Higher bud drop, flower wastage and insect infestation on fruits decreased the fruit production. The present investigation has attempted to analyze the phenology, floral biology, pollination biology, fruit set and insect infestation on Syzygium myhendrae , an endemic and endangered semievergreen tree in the Western Ghats, India. This tree exhibited a bi-annual mode of flowering and fruiting behavior. The flowers lack strong fragrance, colorful and attractive petals, or sepals; however, the dense stamens functioned as a major floral advertisement. The flowers were exclusively visited by insects ( Apis dorsata, A. mellifera, A. cerana, A. florea, Tetragonula iridipennis , wasps, psyllids and beetles). Among these, A. dorsata was the most frequent and effective pollinator. The infestation by Eulophid and Pteromalid wasps has limited the fruit set rate and induced premature fruit drop in S. myhendrae. The damage incidence has ranged from 82% to 100%. Higher bud drop, flower wastage and insect infestation on fruits have resulted in lower fruit production in S. myhendrae . This endangered tree has reproduced via outcrossing using stamen advertisement and pollen rewards. Eventually, higher flower wastage and fruits infestation have resulted in lesser fruit production, seed maturation and seedling establishment. These factors might have jointly resulted in the reproductive failure and limited distribution of this endemic and endangered species.

Mating pattern and pollen dispersal in an advanced generation seed orchard of Cunninghamia lanceolata (Lamb.) Hook.

Seed orchards represent the link between forest breeding and conifer production forests, and their mating patterns determine the genetic quality of seed orchard crops to a large extent. We genotyped the parental clones and their open pollination offspring in the third-generation seed orchard of Chinese fir using microsatellite markers and observed the synchronization of florescence in the seed orchard to understand the genetic diversity and mating structure of the seed orchard population. Genetic coancestry among parental clones was detected in the third generation seed orchard of Chinese fir, and the genetic diversity of the open-pollinated offspring was slightly higher than that of the parental clones. The external pollen contamination rate ranged from 10.1% to 33.7%, 80% of the offspring were produced by 44% of the parental clones in the orchard, and no evidence of selfing was found. We found that 68.1% of the effective pollination occurred within 50 m, and 19.9% of the effective pollination occurred in the nearest neighbors. We also found that successful mating requires about 30% of florescence overlap between males and females, and there was a significant positive correlation between male reproductive energy and male parental contribution. Our results provide a valuable reference for the management and design of advanced generation seed orchards.

Nectar robbing by bees on the flowers of Volkameria inermis (Lamiaceae) in Coringa Wildlife Sanctuary, Andhra Pradesh, India

Floral traits that shape the floral architecture are important to allow or disallow flower visitors to access nectar and effect pollination. Specialization in floral architecture is vulnerable to flower visitors that exploit nectar by robbery without effecting pollination. In Coringa Wildlife Sanctuary in Andhra Pradesh, India, studies on the exploitation of nectar by robbery in plant species with specialized flowers are completely lacking. We carried out a study on the foraging activity of insect foragers and nectar robbing by bees on the specialized nectariferous flowers of an evergreen shrub, Volkameria inermis growing in the landward side of this sanctuary. Field observations indicated that the flowers of this species facilitate legitimate probing only by butterflies and diurnal moths which while seeking nectar effect pollination. However, two bee species Anthophora dizona and Xylocopa pubescens seek nectar illegitimately as primary nectar robbers by making a slit/hole into the corolla tube from outside bypassing the flower front. Additionally, A. dizona gathers pollen legitimately from the stamens which are exposed and placed outside the corolla tube. The stigma is also placed outside the corolla tube but this bee indiscriminately makes attempts to collect pollen from the stigma, as a result of which pollination occurs. Nectar robbing by these bees leads to a reduction in nectar volume in robbed flowers and brings about variability in the standing crop of nectar. As a result, the pollinating butterflies increase the number of nectar foraging visits and shuttle between populations of V. inermis in quest of more nectar to meet their daily metabolic requirements. Such a foraging behavior increases pollination rate in general and cross-pollination in particular, which in turn increases plant fitness in V. inermis. Therefore, the nectar robbing by bees appears to have a positive effect on plant fitness through change in seed set rates.

Effective Behavior of Insects Pollinators of Flowers in Gadung Mango Clone 21 Variety

Pollinating insects are referred as support services, namely services by the processes in the ecosystems that support human well-being by maintaining or enhancing ecosystem services. The availability of flowers, diversity, and behavior of visiting pollinator insects affect the effectiveness of pollination to increase the formation of fruit sets of mango plants. The purpose of this study is to observe the behavior of pollinator insects visiting the mango gadung clone 21 varieties and their effectiveness in increasing the formation of fruit sets. Research has been carried out on two flower seasons: March-May (Off season) and July-September (On season) 2020. Visiting behaviors observed were the number of visits per minute (foraging rate) and the length of visit per flower (flower handling time). Pollination effectiveness was measured from the number of fruit sets formed from the open flower panicles and confined with a tangerine gauze. The results of the study obtained seven species including Apis sp., Trigona sp., Xylocopa sp., Polistes sp. 1, Polistes sp. 2, Chrysomya sp., and Eristalis sp. Visits of pollinating insects on the highest number of mango panicle flowers were (31.69 ± 7.69) flowers / 60 seconds by Trigona sp insects, and the lowest numbers were (2.70 ± 0.67) flowers / 60 seconds by Eristalis sp. insects. The longest visits of pollinator insects on mango flowers were obtained by Eristalis sp for (25.3 ± 8.50) sec/individual/flower and the shortest visits were by Trigona sp for (1.8 ± 0.63) seconds/individual/flower. Insect pollination increases fruit formation by 267.5%. Keywords: insect visits, pollinating insects, fruit formation, gadung 21 varieties mango

Factors Driving Autumn Quercus Flowering in a Thermo-Mediterranean Area

The flowering period of plants is a critical time since it determines their reproductive success. Flowering is controlled by different factors including genetic regulation and environmental conditions. In the Mediterranean area, favourable conditions usually occur in spring, when most plant species flower including those of the Mediterranean Quercus genus. This paper reveals and analyses an unusual and lesser-known phenomenon occurring in the two main Mediterranean agroforestry ecosystems of South Europe, the Mediterranean forest and “dehesa”, that is, a second flowering occurring in autumn for the species Quercus ilex subsp. ballota (holm oak). The continuous pollen monitoring of the atmosphere in the city of Cordoba (southern Spain) for 25 years, together with field phenological observations in the area, has indicated that, apart from the main pollination period in spring, secondary flowerings also occasionally occur in this area, specifically in autumn. The present work examines these uncommon pollination events detected in the autumns of certain years with the aim of determining the main environmental factors that influence and control them. During the 25-year study period, there were 7 years in which a secondary Quercus flowering was detected in the area from the second half of October until the end of November. The univariate statistical analysis of the influence of environmental variables determined that the meteorological conditions in September were the most influential. Low mean temperatures, together with record rainfall in that month, led to autumn flowering events. The phenological characteristics of the spring pollen season were also influential. In the years with a shorter spring, the Quercus pollen season tended to present autumn flowerings. A multivariate adaptive regression splines (MARS) model was built to explain the effects of the different variables on the occurrence of autumn pollination. The results indicated that the combined effect of three predicting variables, September rainfall, the length of the spring pollen season, and the end of the spring pollen season, explained 92% of the variance. The validation showed a strong relationship between the expected and the observed autumn pollen concentrations. Therefore, the present analysis of a long-term pollen database revealed that the main causes of this unusual second flowering in autumn were strongly related to climate change, i.e., strong dry summers and warm autumns. In addition, the results showed that the phenomenon was more frequent in the years with low pollination during spring due to different meteorological events potentiated by climate change, such as dryness or heavy rain episodes, as a way of ensuring acorn crops. The results explain how this unusual and lesser-known phenomenon in agroforestry dynamics is related to the adaptation to climate change and the main factors that are driving it, as well as the potential consequences for these important and endangered Mediterranean ecosystems.

Neutral processes related to regional bee commonness and dispersal distances are important predictors of plant–pollinator networks along gradients of climate and landscape conditions

Understanding how niche‐based and neutral processes contribute to the spatial variation in plant–pollinator interactions is central to designing effective pollination conservation schemes. Such schemes are needed to reverse declines of wild bees and other pollinating insects, and to promote pollination services to wild and cultivated plants. We used data on wild bee interactions with plants belonging to the four tribes Loteae, Trifolieae, Anthemideae and either spring‐ or summer‐flowering Cichorieae, sampled systematically along a 682 km latitudinal gradient to build models that allowed us to 1) predict occurrences of pairwise bee–flower interactions across 115 sampling locations, and 2) estimate the contribution of variables hypothesized to be related to niche‐based assembly structuring processes (viz. annual mean temperature, landscape diversity, bee sociality, bee phenology and flower preferences of bees) and neutral processes (viz. regional commonness and dispersal distance to conspecifics). While neutral processes were important predictors of plant–pollinator distributions, niche‐based processes were reflected in the contrasting distributions of solitary bee and bumble bees along the temperature gradient, and in the influence of bee flower preferences on the distribution of bee species across plant types. In particular, bee flower preferences separated bees into three main groups, albeit with some overlap: visitors to spring‐flowering Cichorieae; visitors to Anthemideae and summer‐flowering Cichorieae; and visitors to Trifolieae and Loteae. Our findings suggest that both neutral and niche‐based processes are significant contributors to the spatial distribution of plant–pollinator interactions so that conservation actions in our region should be directed towards areas: near high concentrations of known occurrences of regionally rare bees; in mild climatic conditions; and that are surrounded by heterogenous landscapes. Given the observed niche‐based differences, the proportion of functionally distinct plants in flower‐mixes could be chosen to target bee species, or guilds, of conservation concern.

The Beneficial Effects of Insect Pollination and Biochar Seed Coating on Okra (Abelmoschus esculentus) Seed Quality at Varying Temperature Conditions

Underutilized crops, such as okra, have the potential to alleviate stress on crop production imposed by climate change and farming conditions, but their production is greatly hindered by poor seed quality. Insect pollination and seed coating with organic substances (biochar) may improve okra’s seed performance, but the beneficial effects of biochar seed coating and pollination on the seed quality of okra grown under stressful conditions is unknown. We examined the impact of pollination and biochar seed coating on okra seed performance under varying temperatures. Seeds were obtained from plants grown under complete insect pollination and exclusion. A factorial experiment was conducted in growth chambers with three factors: seed type, seed coating and temperature conditions. Insect-pollinated seeds with biochar coating had the highest chlorophyll content, seedling vigour index, shoot, and root growth and the heaviest seedling mass, but with a reduced speed of germination and emergence. The insect-pollinated seed without biochar coating had a lighter seedling mass (33% lower) than insect-pollinated, coated seed. Low temperature conditions during germination were ameliorated by biochar seed coating but biochar coating could not alleviate high temperature (35/30 °C) stress. Harnessing the pollinator’s benefits and biochar seed coating are possible sustainable solutions to enhance seed quality.

Effective hawkmoth pollination in the primarily bee‐pollinated Salvia daiguii—an example of adaptive generalization

AbstractMany plants exhibit floral traits that are directed to specific pollinator groups. Nevertheless, they can also attract less‐adapted pollinators and gain benefits under certain conditions, resulting in adapted generalization. This may be the case in Salvia daiguii (Lamiaceae), an endangered, bee‐pollinated species native to the Tianmenshan National Forest Park, China. The flower appears phenotypically specialized to bees but is also visited by Macroglossum bombylans. In the present study, we test whether the moth is an effective pollinator of S. daiguii. We quantified and compared the frequency of flower visits by bees and moths and the number of pollen grains deposited on the stigma after a single visit. We also recorded the movements of pistils and stamens of S. daiguii and the behavior of the hawkmoth at the flowers. We found that Apis cerana was the predominant pollinator, depositing an average of 4.74 pollen grains on the stigma after a single visit. However, as the style bends downward during anthesis and reaches the same level as the anthers, Macroglossum individuals hovering around the flowers were also able to effectively transfer pollen to the stigma. On average, 1.38 pollen grains were deposited on the stigma during a single visit. We demonstrate for the first time that the hawkmoth is an effective secondary pollinator in the primarily bee‐pollinated S. daiguii. Style bending allows a nectar thief to become a secondary pollinator. The extent of pollinator generalization is thus increased without affecting the fundamental phenotype adapted to bees as the main pollinators.

Evidence for the recruitment of florivorous plant bugs as pollinators

Angiosperm flowers and their animal visitors have co-evolved for at least 140 Ma, and early flowers were likely used mainly as mating and feeding sites by several groups of insects, including beetles, flies, true bugs, and thrips. Earlier studies suggested that shifts from such neutral or antagonistic relationships toward mutualistic pollination interactions between flowers and insects occurred repeatedly during angiosperm evolution. However, the evolutionary mechanisms and adaptations, which accompanied shifts toward effective pollination, are barely understood, and evidence for such scenarios has been lacking. Here, we show that Syngonium hastiferum (Araceae), a Neotropical representative of an otherwise beetle-pollinated clade, is pollinated by plant bugs (Miridae; Heteroptera), which are florivores of Syngonium schottianum and other Araceae species. We found that S.hastiferum differs in several floral traits from its beetle-pollinated relatives. Scent emission and thermogenesis occur in the morning instead of the evening hours, and its pollen surface is spiny instead of smooth. Furthermore, the floral scent of S.hastiferum includes a previously unknown natural product, (Z)-3-isopropylpent-3-en-1-ol, which we show to have a function in specifically attracting the plant bug pollinators. This is the first known case of a specialized plant bug pollination system and provides clear evidence for the hypothesis that the adoption of antagonistic florivores as pollinators can drive flower diversification. VIDEO ABSTRACT.

Disruptive selection via pollinators and seed predators on the height of flowers on a wind-dispersed alpine herb.

Floral stalk height is known to affect seed dispersal of wind-dispersed grassland species, but it may also affect the attractiveness of flowers and fruits of animal-pollinated and animal-dispersed plants. Stalk height may thus be responsive to selection via interactions with both mutualist pollinators and seed dispersers, but also antagonist florivores and seed predators. In this study, we aimed to determine the effect of pollinators and seed predators on selection on floral stalk height in the insect-pollinated and wind-dispersed, alpine, andromonoecious herb Pulsatilla alpina, whose flowers also vary in their sex allocation and thus in the resources available to both mutualists and antagonists. We measured the resource status of individuals in terms of their size and the height of the vegetation surrounding plants of P. alpina at 11 sites. In one population, we recorded floral stalk height over an entire growing season and investigated its association with floral morphology and floral sex allocation (pistil and stamen number) and used leaf-removal manipulations to assess the effect of herbivory on floral stalk height. Finally, in four populations, we quantified phenotypic selection on floral stalk height in four female components of reproductive success before seed dispersal. Stalk height was positively associated with female allocation of the respective flower, the resource status of the individual, and the height of the surrounding vegetation, and negatively affected by leaf removal. Our results point to disruptive selection on stalk height in terms of both selection differentials and selection gradients for fertilization, seed predation, and seed maturation rates and to positive selection on stalk height in terms of a selection differential for mature seed number. Stalk height of P. alpina is a costly trait that affects female reproductive success via interactions with both mutualists and antagonists. We discuss the interplay between the resource status and selection imposed on female reproductive success and its likely role in the evolution of sex-allocation strategies, especially andromonoecy.

Pollinator efficiency of avocado (Persea americana) flower insect visitors

Abstract Pollination services from insects are important for higher yield and better fruit quality in avocado (Persea americana Mill.). Measuring pollinator effectiveness is significant for capturing the relative contributions of different insect taxa to pollination services and for identification of the most important pollinators of this globally important crop. In the present study, we tested pollinator efficiency of avocado in Kenya based on pollen deposition after single visits of flowers by different pollinator species and visitation frequency. We monitored the pollination frequency during the flowering period replicated across six farms. Three trees were selected per farm, each with five flower panicles. Out of the 14 observed insect flower visitor species, pollen deposition efficiency was highest in the Western honey bee (Apis mellifera L.), followed by the hover fly species (Phytomia incisa W.). These two species had both the highest pollen deposition and pollen grain loads on their bodies. Furthermore, A. mellifera was the most frequent avocado flower visitor followed by Diptera except hoverflies. Our results imply that A. mellifera can be managed to achieve adequate pollination services for avocado, particularly in areas lacking efficient wild pollinators.

Consequences of pollinator availability and effectiveness for pollen transfer in a gynodioecious seed crop system

Pollinator availability and effectiveness are important considerations in plant systems that depend on insect transfer of pollen. In mixed-flower systems (such as dioecious or gynodioecious systems), pollinators may distinguish between morphs, a behaviour which could have negative implications if it leads to reduced cross-pollination. We examined pollinator visitation, response, and effectiveness in hybrid canola seed production, a gynodioecious crop, to understand how pollinator behaviour contributes to cross-pollination between ‘male’ (hermaphroditic) and ‘female’ (male-sterile) morphs. The pollinator types found in these fields differ in visitation rate, size, and pollen load, factors that may affect pollen transfer between plants. The willingness of pollinators to move between male and female flowers can also affect pollen deposition. We used an interview bouquet to present unvisited female inflorescences to different pollinator types visiting male and female flowers to understand behavioural responses to floral morphs and the factors that contribute to better pollination effectiveness. Managed pollinators (honey and leafcutter bees) were far more abundant than wild pollinators in this system. Bees foraging on male flowers were less likely to accept a proffered female flower than those foraging on female flowers. Pollen deposition on stigmas was influenced by pollinator type (female leafcutter bees were the most effective) and increased with time spent on a flower. Pollinators transferring from a male flower to a female flower deposited more pollen than those that originated on female flowers, emphasizing the importance of transfer between male and female morphs. Surprisingly, pollinators carrying more pollen transferred less pollen to recipient stigmas.