Amount Of Nectar Research Articles

Insect pollinators diversity and abundance in Eruca sativa Mill. (Arugula) and Brassica rapa L. (Field mustard) crops.

Studies on the insect pollinators diversity and their relative abundance in Eruca sativa Mill. (Arugula) and Brassica rapa L. (field mustard) was carried out during spring season from February to April consecutively during all the three years of 2016–18. Insect pollinators observed belonged to four orders i.e. Hymenoptera, Diptera, Lepidoptera, and Coleoptera. A total of 20 major species of insect pollinators were recorded. The highest abundance of pollinator species belonged to Hymenoptera. The most prominent insect pollinator species were Apis mellifera followed by other three honey bee species of A. cerana, A. florea, and A. dorsata respectively. Some species of solitary bees were also recorded. From Diptera, four species of syrphid fly and one species from Muscidae family were also recorded. Insect pollinators recorded from order Lepidoptera were Pieris brassicae, Vanessa cardui, and Papilio demoleus. Lady bird beetle Coccinella septempunctata was recorded from Coleoptera order as occasional visitor. It was noticed that E. sativa attracted more insect pollinators than B. rapa which may be attributed to different amount and chemical properties of nectar, with number of pollen grains, and flower canopy of both crops. Further studies are needed to confirm the reasons for higher pollinator visitation to E. sativa than B. rapa through chemical analysis of nectar, amount of pollens, flower physiology and phenology of both crops.

The Octadecanoid Pathway, but Not COI1, Is Required for Nectar Secretion in Arabidopsis thaliana.

Over 75% of crop species produce nectar and are dependent on pollinators to achieve maximum seed set, yet little is known about the mechanisms regulating nectar secretion. The phytohormone jasmonic acid (JA) is recognized to be involved in several plant processes including development and defense. JA was also recently shown to positively influence nectar secretion in both floral and extrafloral nectaries. For example, endogenous JA levels peak in flowers just prior to nectar secretion, but the details of how JA regulates nectar secretion have yet to be elucidated. We have found that the octadecanoid pathway does indeed play a role in the production and regulation of floral nectar in Arabidopsis. Null alleles for several JA biosynthesis and response genes had significantly reduced amounts of nectar, as well as altered expression of genes known to be involved in nectar production. We additionally identified crosstalk between the JA and auxin response pathways in nectaries. For example, the nectar-less JA synthesis mutant aos-2 showed no auxin response in nectaries, but both nectar production and the auxin response were restored upon exogenous JA and auxin treatment. Conversely, coi1-1, a JA-Ile-insensitive receptor mutant, displayed no auxin response in nectaries under any circumstance, even in older flowers that produced nectar. Surprisingly, opr3-1, a mutant for 12-oxophytodienoate reductase 3 [an enzyme further down the JA biosynthetic pathway that reduces 12-oxo phytodienoic acid (OPDA)], produced no nectar in newly opened flowers, but did secrete nectar in older flowers. Furthermore, a similar phenotype was observed in coi1-1. Cumulatively, these observations strongly suggest an indispensable role for an octadecanoic acid- and auxin-dependent, but JA- and COI1-dispensible, pathway in regulating nectar production in Arabidopsis.

Diversidad de abejas en España, tendencia de las poblaciones y medidas para su conservación (Hymenoptera, Apoidea, Anthophila)

Ortiz-Sánchez, F.J., Aguado Martín, L.O., Ornosa, C. 2018. Bee diversity in Spain. Population trend and conservation measures (Hymenoptera, Apoidea, Anthophila). Ecosistemas 27(2): 3-8. Doi.: 10.7818/ECOS.1315 Bees belong to the order Hymenoptera, superfamily Apoidea, and constitute the monophyletic group Anthophila, originating from sphecoid wasps. There are about 20 000 species described in the world, 3370 in the western Palearctic and nearly 2000 in Europe. The Mediterranean basin is one of the areas with the richest diversity of bees, and in Spain more than 1100 species have been recorded. There are six families of bees in Europe with contrasting body sizes and life histories. Different species show different levels of social organization, from solitary to eusocial, including some parasitic species. Bees can nest in a variety of substrates (soil, rocks, wood, stems). Females collect large amounts of nectar and pollen to provision their nests with food for their offspring. This, together with their high pollinating effectiveness on many wild and cultivated plants, makes bees a keystone group in the functioning of terrestrial ecosystems. Information on the population trends and conservation status is lacking for most species.

A modified artificial bee colony algorithm for load balancing in network-coding-based multicast

This paper studies the load balancing optimization problem in network-coding-based multicast and proposes a modified artificial bee colony algorithm (MABC) to address it. MABC is featured with three novel schemes, including a food source initialization scheme, a novel selection scheme and a neighborhood search scheme. The first scheme generates a set of high-quality food source positions, ensuring that the exploration of the search begins with promising areas in the search space. In the second scheme, a nectar source library (NSL) is used to store a set of best solutions found during the iterative search. Each scout bee produces a new food source based on a food source randomly selected from NSL. This helps to generate food sources with high nectar amounts. The last scheme is a neighborhood search scheme to strengthen population diversity and avoid local optima, where a probability vector is maintained and utilized to carry out fine local exploitation. Experimental results demonstrate that the proposed MABC outperforms a number of state-of-the-art evolutionary algorithms with respect to the quality of solutions obtained.

Natural selection methods for artificial bee colony with new versions of onlooker bee

Artificial bee colony (ABC) algorithm is one of the most recent swarm intelligence-based algorithms simulate the foraging behavior of honey bees in their hive. ABC starts with a colony of artificial bees with sole aim of discovering the place of food sources with high nectar amount using the solution search equation in the employed bee and onlooker bee operators. However, the solution search equation is good in exploration and poor in exploitation. In this paper, the solution search equation of the onlooker bee is modified by using a value of the fittest food sources selected by a set of selection schemes inspired from the evolutionary algorithms. This is to guide the search process of onlooker bee toward the fittest food sources from the population in order to empower the exploitation capability and convergence. Four selection schemes are incorporated with the ABC algorithm to choose the fittest food sources in four versions as follows: global-best, tournament, linear rank, and exponential rank. For evaluation purposes, 10 classical benchmark optimization functions are used to study the sensitivity analysis of each ABC algorithm to its parameters. The performance of the proposed ABC versions is compared with the original ABC version in order to study the effectiveness of the modifications. In addition, a comparative evaluation of ABC algorithms is carried out against the state-of-the-art methods that worked on CEC2005 benchmark functions, CEC2015 benchmark functions, and two real-world cases of economic load dispatch problem. The experimental results show that the selection schemes incorporated within the search equation of the onlooker bee directly affects the performance of ABC algorithm.

Micromorphological and histochemical attributes of flowers and floral reward in Linaria vulgaris (Plantaginaceae)

The self-incompatible flowers of Linaria vulgaris have developed a range of mechanisms for attraction of insect visitors/pollinators and deterrence of ineffective pollinators and herbivores. These adaptive traits include the flower size and symmetry, the presence of a spur as a “secondary nectar presenter,” olfactory (secondary metabolites) and sensual (scent, flower color, nectar guide—contrasting palate) signals, and floral rewards, i.e. pollen and nectar. Histochemical tests revealed that the floral glandular trichomes produced essential oils and flavonoids, and pollen grains contained flavonoids, terpenoids, and steroids, which play a role of olfactory attractants/repellents. The nectary gland is disc-shaped and located at the base of the ovary. Nectar is secreted through numerous modified stomata. Nectar secretion began in the bud stage and lasted to the end of anthesis. The amount of produced nectar depended on the flower age and ranged from 0.21 to 3.95 mg/flower (mean = 1.51 mg). The concentration of sugars in the nectar reached up to 57.0%. Both the nectar amount and sugar concentration demonstrated a significant year and population effect. Pollen production was variable between the years of the study. On average, a single flower of L. vulgaris produced 0.31 mg of pollen. The spectrum of insect visitors in the flowers of L. vulgaris differed significantly between populations. In the urban site, Bombus terrestris and Apis mellifera were the most common visitors, while a considerable number of visits of wasps and syrphid flies were noted in the rural site.

Flowering and Nectar Secretion in two Forms of the Moldavian Dragonhead (Dracocephalum moldavica L.) – A Plant with Extraordinary Apicultural Potential

Abstract Dracocephalum moldavica is a valuable reward plant for flower visitors. The aim of the study was to ecologically characterise its flowers and leaves and assess the seasonal and daily dynamics of flowering in two white- and blue-flowered forms of this species in 2004 and 2005. Additionally, the duration and abundance of plant flowering as well as the nectar amount and sugar content were analysed. The signalling attractants of the plant include an intense scent emitted by trichomes located not only on its flowers but also on its stem and leaf surfaces. The average corolla length is 24 mm and the corolla tube, which can be completely filled with nectar, is 8.6 mm long. The floral lifespan was shown to reach 2-3 days and the mean blooming duration of both forms of dragonhead 45-48 days. The white-flowered plants produced a substantially greater number of flowers (5352) than the blue-flowered form (2965). The nectar amount obtained from ten blue flowers was 15.33 mg and that extracted from white flowers reached 17.56 mg, with 49.4% and 51.5% content of sugar, respectively. The total sugar mass produced by one white-flowered plant was 4656 mg, while one blue-flowered plant yielded 2164 mg of sugars. The sugar yield calculated in the study for the white-flowered form (586 kg · ha−1) was two-fold higher than that in the blue-flowered plants.

Взаємодія представників роду Buddleja L. з комахами-запилювачами

Наведено дані щодо особливостей запилення представників роду Buddleja L. На основі аналізу літературних даних описано концепції "синдрому запилення", що базуються на конкретних ознаках квіток: форма, колір, запах, розмір. Запропоновано дані концепції такими вченими, як: F. Delpino, S. Vogel в модифікації L. Van der Pijl та K. Faegri, W. N. Ellis, A. C. Ellis-Adam, H. Muller. Дослідження проведено зі січня по серпень 2011–2012 р. в китайсько-гімалайському регіоні Сичуань та Юньнань, адже саме цей регіон є частиною глобального осередку зростання великого різноманіття видів роду та вторинним центром походження азіатських видів. Для досліджень було обрано 5 видів роду Buddleja L.: B. asiatica Lour., B. crispa Benth., B. forrestii Diels, B. macrostachya Benth. та B. myriantha Diels. Описано зв'язок між морфологічною будовою квітки досліджуваних рослин та анатомічною будовою ротових апаратів запилювачів. Наведено склад ароматичних сполук квітів Buddleja L. З'ясовано, які комахи-запилювачі найчастіше відвідують досліджувані рослини. Основними запилювачами були бджоли, джмелі. Усі досліджувані види мають вузьку, довгу трубку віночка з прихованим нектаром. Із досліджень видно, що первинними запилювачами всіх видів роду є бджоли, а не метелики. Лише B. crispa Benth. приваблює метеликів. B. davidii Franche. запилюється переважно метеликами та міллю та дуже рідко бджолами. Також, на основі літературних джерел, було описано хімічний склад запаху квіток. На основі спостережень було виявлено, що найчастішими відвідувачами цих рослин як у Північній, так і в Південній Америці є медоносні бджоли, мухи, дзюрчалки, джмелі, оси та зрідка метелики, особливо головчаки. Охарактеризовано особливості кольорової гами квіток видів роду Buddleja L. З'ясовано вплив кількості нектару та його хімічний склад на приваблення запилювачів. Отже, існує чимало концепцій "синдрому запилення". Однією з найпопулярніших є типологія, яку запропонували W. N. Ellis, A. C. Ellis-Adam.

Current and previous spatial distributions of oilseed rape fields influence the abundance and the body size of a solitary wild bee, Andrena cineraria, in permanent grasslands.

Wild bees are essential pollinators whose survival partly depends on the capacity of their environment to offer a sufficient amount of nectar and pollen. Semi-natural habitats and mass-flowering crops such as oilseed rape provide abundant floristic resources for bees. The aim of this study was to evaluate the influences of the spatial distribution of semi-natural habitats and oilseed rape fields on the abundance and the mean body size of a solitary bee in grasslands. We focused on a generalist mining bee, Andrena cineraria, that forages and reproduces during oilseed rape flowering. In 21 permanent grasslands of Eastern France, we captured 1 287 individuals (1 205 males and 82 females) and measured the body size of male individuals. The flower density in grasslands was quantified during bee captures (2016) and the landscape surrounding grasslands was characterized during two consecutive years (2015 and 2016). The influence of oilseed rape was tested through its distribution in the landscape during both the current year of bee sampling and the previous year. Bee abundance was positively influenced by the flower density in grasslands and by the area covered by oilseed rape around grasslands in the previous year. The mean body size of A. cineraria was explained by the interaction between flower density in the grassland and the distance to the nearest oilseed rape field in the current year: the flower density positively influenced the mean body size only in grasslands distant from oilseed rape. A. cineraria abundance and body size distribution were not affected by the area of semi-natural habitats in the landscape. The spatial distribution of oilseed rape fields (during both the current and the previous year) as well as the local density of grassland flowers drive both bee abundance and the mean value of an intraspecific trait (body size) in permanent grasslands. Space-time variations of bee abundance and mean body size in grasslands may have important ecological implications on plant pollination and on interspecific interactions between pollinators. Specifically, a competition between bee species for nesting sites might occur in oilseed rape rich landscapes, thus raising important conservation issues for bee species that do not benefit from oilseed rape resources.

Nectar secretion of RN-type cytoplasmic male sterility three lines in soybean [Glycine max (L.) Merr.

Significant progress has been achieved in the use of heterosis in soybean and several soybean hybrids have been released in China. However, broad use of hybrid soybean seed is limited due to low seed setting of female parents. Breeding cytoplasmic male sterile (CMS) lines with high out-crossing rate is necessary to solve the problem. The objective of this study was to determine the relationship between out-crossing rate of CMS lines and their nectar secretion. The daily nectar secretion rhythm, meteorological effect on nectar secretion, and differences in nectar secretion among genotypes and years were investigated in 27 soybean CMS lines (A-lines) with their maintainers (B-lines) and restorers (R-lines). The correlation between out-crossing rate of CMS lines and nectar production was also evaluated. Nectar secretion had diurnal variation. Secretion initiated at about 06:00 for most materials and reached a peak at 07:00–08:30 after flower opened, then the nectar secretion decreased gradually. A sub-peak appeared at about 13:00, while the nectar could not be detected at 17:00. Nectar secretion was greatly influenced by the weather conditions. The amount of nectar secretion increased gradually over time during periods of high temperature and no rainfall for several days. Rainy weather and low temperatures inhibited nectar secretion. There were obvious variations of nectar amount among different genotypes tested. Significant nectar variation within a genotype among years was also observed, and the highest nectar secretion was 3-fold higher than the lowest. The amount of nectar secretion from R-lines was significantly higher than that of A- and B-lines. There was no significant difference in nectar secretion between A- and B-lines. A- and B-lines with higher out-crossing rates secreted more nectar. The amount of nectar secretion of A- and B-lines were significantly positively correlated with the out-crossing rate of A-lines.

Functional specialization and phenotypic generalization in the pollination system of an epiphytic cactus

ABSTRACT Plant-pollinator interactions range from obligatory specialists to facultative generalists, and floral morphology and pollination system may not match completely. The floral biology, reproductive system and floral visitors of a species of the tribe Rhipsalideae were investigated with a focus on the consistency between the pollination system and the floral phenotype. Rhipsalis neves-armondii is an obligate xenogamous species, due to self-sterility. Its flowers are white, small and diurnal, and radially symmetrical. These features, along with their small amount of nectar, characterize the flowers as phenotypic generalists. The most frequent pollinators were a solitary oligolectic species of Andrenidae (Rhophitulus solani), two species of Meliponinae (Trigona spinipes and T. braueri) and Apis mellifera. Despite the generalist floral phenotype, the pollination system is functionally specialized, since only small bees performed effective visits. Flowers of R. neves-armondii may represent a case of cryptic floral specialization in which attributes other than morphology act as filters, restricting them to a single functional group of pollinators. Moreover, the four most frequent species of pollinators cover a spectrum ranging from solitary oligolectic to social polylectic bees, including an exotic species. These results illustrate the distinct dimensions of specialization-generalization that may occur in the pollination process of a single species.

Floral Trait Variations Among Wild Tobacco Populations Influence the Foraging Behavior of Hawkmoth Pollinators

Most pollinators visit flowers in the search of nectar rewards. However, as the floral nectar can often not be directly detected by pollinators, many flower visitors use secondary metabolites such as odor- or taste-proxies to anticipate nectar quantity and quality. Plants might exploit these sensory inferences of the pollinator to increase their pollination rates without increasing their caloric investment into their floral rewards. Here we investigated the effects of natural variation in certain primary and secondary floral metabolites in three populations of the wild tobacco, Nicotiana attenuata, on the pollination behavior of the hawkmoth Manduca sexta. Although offering the same caloric value per flower, the plants of these populations differ in the compositions and concentrations of sugars within the nectar. Moreover, the flowers of these plants emitted highly contrasting levels of attractive floral volatiles (benzyl acetone), but did not differ in the amounts of defensive nectar metabolites (nicotine). In wind tunnel assays with M. sexta moths, plants from those populations that released the largest amount of benzyl acetone as well as those that had a higher ratio of nectar sucrose were more frequently visited and re-visited by the hawkmoth. High emissions of benzyl acetone additionally correlated with a higher time investment of the moths into individual flowers on each visit, leading to the largest foraging success of the moths on those flowers that were most strongly scented. We propose that it is the variation of flower metabolites and their detection by the pollinator rather than the actual caloric value of the nectar, which determines pollinator visitations to a certain flower population. Hence, plants could potentially create a specialist pollinator community by altering their floral signals, either by producing volatiles that pollinators prefer or by providing nectar sugars that pollinators are most sensitive to, while at the same time keeping the caloric value of their nectar rewards at a constant level. These findings highlight the importance of variations among floral signals and their detection by specific pollinators for plant diversification as well as for the evolution of specific plant-pollinator interactions.

Unravelling host-mediated effects on hemiparasitic Mexican mistletoePsittacanthus calyculatus(DC.) G. Don traits linked to mutualisms with pollinators and seed dispersers

While the influence of mistletoe–host interactions on each other’s evolution is well-recognized, the role of interactions between mistletoes and its mutualistic pollinators and seed dispersers mediated by host species is relatively unexplored. Here, we examine the effects of host species (Mexican hawthorn Crataegus mexicana DC, black cherry Prunus serotina Ehrh., leather-leaf Mexican oak Quercus crassipes Bonpl.) on flower morphology, nectar production, pollinator visitation rate and female reproductive fitness in hemiparasitic Mexican mistletoe Psittacanthus calyculatus (DC.) G. Don (Loranthaceae) populations at three different locations. We first measured the lengths of corolla, style, stamen, exerted stamen and anther, the length and width of the ovary and nectar availability for mistletoe flowers in natural populations. Then, we evaluated flower visitation and measured (length and width) and weighed the fruits and its seeds of mistletoes growing on each of the three host species. Finally, we evaluated the effects of host species, location and flower traits on fruit or seed size variation (both as proxies of reproductive fitness). We found mistletoes growing on natural hosts P. serotina and Q. crassipes produced larger flowers, fruits and seeds than mistletoes on cultivated C. mexicana. However, these differences varied across space. The amount of available nectar and hummingbird visitation rates in flowers of mistletoes on C. mexicana was higher at the three sites than in flowers of mistletoes on P. serotina or Q. crassipes. The effects of host species, study site and floral trait covariates affected significantly all fitness measures, indicating that mistletoes’ reproductive fitness is affected differently depending on the host species and their site of occurrence. These host-associated differences in reproduction might have implications for interactions with mutualistic vectors.

Honey bee nectar foragers feeding themselves and the colony: a review in support of dietary exposure assessment

Quantitative knowledge regarding the foods collected and ingested by nectar foraging honey bees (Apis mellifera) is essential for accurately assessing risk associated with pesticide residues in their diet. Although a very large and diverse body of research is available covering many years of research in the literature, much of this research was designed for purposes other than risk assessment and the accumulated knowledge has not been comprehensively reviewed and consolidated from the viewpoint of pesticide risk assessment. Accordingly, in the interest of advancing all tiers of pollinator risk assessment, and identifying data gaps, we strove to gather, assess, and summarize quantitative data relating to nectar forager collection, consumption and sharing of nectar within the colony. Data pertaining to nectar forager provisioning before foraging flights, quantities of nectar brought back to the hive, frequency and duration of foraging trips and energetics was reviewed. Recommendations for future research in support of refined honey bee risk assessment will be discussed.

Key biological factors related to outcrossing-productivity of cytoplasmic-nuclear male-sterile lines in soybean [Glycine max (L.) Merr.

Soybean scientists in China have tried to utilize heterosis for yield enhancement. A number of cytoplasmic-nuclear male-sterile (CMS) lines, their maintainers and restorers were developed, but the commercialized hybrid seed production is still a bottleneck. Five soybean CMS lines with their maintainers and restorers were studied for the sufficiency of viable and effective pollens from maintainers/restorers, the natural insect pollinators in fields and outcrossing capacity of CMS lines. The results showed that the maintainers/restorers may offer viable pollens during the flowering day time in Nanjing and Taiyuan (germination rate 77.8–86.5%). But the morning dew causes pollens losing effectiveness in Nanjing, while normal in Taiyuan, indicating the location and planting season without morning dew is a key for CMS/hybrid seed production. In CMS fields in Taiyuan, the major insect pollinators composed of China bee (54.3%), Mellifera bee (11.3%), Northern-cutting bee (6.0%), Corn belt hair bee (1.5%), etc. A parallel trend between insect number and flower nectar amount in a day with peak time at 12:00–13:00 implied the soybean nectar attracting the insects. The outcrossing pod-set rate of CMS lines in net-room with artificial-raised bees, net-room without bees and open-field with enhanced natural insects was 57.8, 2.1 and 47.3%, respectively, indicating that insect pollination is necessary. The realized outcrossing pod-set rate in seed production field achieved 88.9% (1460.4 kg/ha) for SXJLCMS1A × SXJLCMS1B and 145.2% (1829.5 kg/ha) for SXCMS1A × JY-31, different outcrossing capacity existed among CMS lines. Thus the CMS/hybrid seed production can be improved through optimizing the pollen effectiveness, pollinator population and talented CMS line.

Robinia pseudoacacia L. Flower Analyzed by Using An Unmanned Aerial Vehicle (UAV)

Tree flowers are important for flower–insect relationships, seeds, fruits, and honey production. Flowers are difficult to analyze, particularly in complex ecosystems such as forests. However, unmanned aerial vehicles (UAVs) enable detailed analyses with high spatial resolution, and avoid destruction of sensitive ecosystems. In this study, we hypothesize that UAVs can be used to estimate the number of existing flowers, the quantity of nectar, and habitat potential for honeybees (Apis mellifera). To test this idea, in 2017 we combined UAV image analysis with manual counting and weighing of the flowers of eight-year-old black locust (Robinia pseudoacacia L.) trees to calculate the number of flowers, their surface area, and their volume. Estimates of flower surface area ranged from 2.97 to 0.03% as the flying altitude above the crowns increased from 2.6 m to 92.6 m. Second, for the horizontal analysis, a 133 m2 flower area at a one-hectare black locust plantation was monitored in 2017 by a UAV. Flower numbers ranged from 1913 to 15,559 per tree with an average surface area of 1.92 cm2 and average volume of 5.96 cm3. The UAV monitored 11% of the total surface and 3% of the total volume. Consequently, at the one-hectare black locust study area we estimate 5.3 million flowers (69 kg honey), which is sufficient for one bee hive to survive for one year.

Impact of floral nectar limitation on life-history traits in a grassland butterfly relative to nectar supply in different agricultural landscapes

Wild flower diversity and abundance are strongly reduced in intensive agricultural landscapes. Flower-visiting insects may, therefore, experience limited nectar quantities and qualities. Adult insects that rely on energy-rich nectar income for flight, survival and reproduction are expected to be much more affected than insects that rely on their larval reserves. We dealt with this issue at the intraspecific level by comparing the responses of several life-history traits to different nectar diets between meadow brown butterflies (Maniola jurtina) originating from relative intensively managed and extensively managed agricultural landscapes. We used outdoor flight cages in which we simulated factorial treatments of low/high nectar quality and low/high quantity. Survival was highest in the high nectar quantity and quality treatment. Individuals from intensive landscapes were heavier, which is in line with predictions on increased capital breeding, and they survived better than those from extensive landscapes, of which the females lost body mass in all treatments. Females from intensive landscapes were able to buffer, or even increase, their body mass in the high nectar quantity treatments, but the differences with females from extensive landscapes disappeared under low nectar quantities (independent of nectar quality). In males, body mass losses were always larger for individuals from extensive landscapes compared to individuals from intensive landscapes. Forty percent of the females showed complete reproductive failure in the low quantity/low quality treatment compared to c. 7% in the other treatments. In the low quantity/low quality treatment, realized fecundity decreased strongly in females from intensive, but not extensive landscapes. Egg size was not affected by landscape of origin in the high-quality nectar treatments, but showed very different responses relative to landscape of origin in the treatments with low-quality nectar. Our results showed strong effects of reduced nectar supply on fitness-related traits, and responses were different between butterflies originating from landscapes with contrasted nectar diet. Hence, different levels of agricultural intensification changing the quantity and quality of the local nectar supply could pave the way for ecological differentiation of the organism’s behaviour, physiology and life history.

Ecological aspects of the floral structure and flowering in Pulsatilla species

In terms of flowering ecology, <em>Pulsatilla</em> flowers are classified as “pollen flowers” producing inconsiderable amounts of nectar. The aim of this study was to assess the length of the flowering period in <em>Pulsatilla slavica</em> and <em>P. vulgaris</em> and to investigate the structure of the epidermis of the perianth and generative elements of their flowers. Special focus was placed on the structure of hairs and the distribution of stomata. The weight of nectar released by the flowers of the two <em>Pulsatilla</em> species and the content of sugars in the nectar was also evaluated. In SE Poland, both species flowered for similar periods between the second half of April and the first half of May. The flower life-span of both was determined to be 9–14 days. The lower part of each sepal was observed to be covered by long hairs having cellulose-pectin cell walls of varying thickness. Hairs present on the pistil style are thinner; they may provide some protection against cold and can play a role of a secondary pollen presenter for insects. The bowl-shaped structure of the perianth and the nature of the adaxial surface of the sepal epidermis may facilitate reflection of sunlight into the inner parts of the flower, which may contribute to an elevation of the intraflower temperature. This is particularly important for the functionality of the ovary. The surface of the hairs was seen to be covered by a cuticle ensuring water impermeability. Flowers are visited by honeybees, bumblebees, butterflies, and ants, for which nectar and pollen are the main attractants. Ants, which are regarded as illegitimate flower visitors, were found to cause damage to the androecium. The number of fruits produced in the flowers of both <em>Pulsatilla</em> species was lower than 50% of the number of pistils.

Crop management affects pollinator attractiveness and visitation in oilseed rape

Ecological intensification of agriculture implies managing ecological processes to improve performance of agricultural systems. However, impacts on relevant ecological functions such as insect pollination from other crop management factors are poorly explored. Pest insects and crop resources such as water availability can directly affect crop yields, but it is unknown if there are indirect effects through effects on insect pollination. With a factorial experiment, we examined how irrigation and control of pollen beetles affected crop attractiveness and pollinator visitation in an open-pollinated spring oilseed rape cultivar. We studied how irrigation and pest control modified the production of flowers and nectar in oilseed rape, and if this in turn affected the flower-visitation of honey bees and bumble bees. Pest control increased the number of oilseed rape flowers by 69%, and the amount of nectar per flower with 36%, but for the latter only in non-irrigated plots. Furthermore, we found higher pollinator densities in plots with reduced pollen beetle densities. Pest control also reduced the number of non-legitimate flower visits, suggesting higher pollination efficiency in plots with reduced pollen beetle densities. We show that crop management affects the value of mass-flowering crops as a resource for pollinating insects. Development of pest control tools that are harmless to pollinators could increase the value of flowering crops as food resources for pollinating insects.

Floral signals and filters in a wasp- and a bee-pollinated Gomphocarpus species (Apocynaceae: Asclepiadeae)

Floral traits may function as attractants for some flower visitors and also as mechanisms that filter out non-beneficial flower visitors. Our current understanding of floral filter mechanisms is limited as this particular aspect of floral function has received less attention than floral attractants. Here we report on a case of two closely related Gomphocarpus species, G. physocarpus and G. fruticosus, that are similar in their general floral shape and architecture but differ in their main pollinators, which are vespid wasps and honeybees, respectively. To identify the floral traits that best explain the observed pollinators we analysed and compared the floral scent composition, the flower colour, flower morphology, and nectar sugar composition of the two species. Furthermore, the response to floral scent was tested in behavioural experiments with Belanogaster and Polistes vespid wasps. The floral scent composition differed significantly between the plant species. Acetic acid was a main component in the wasp-pollinated G. physocarpus, which is highly unusual for a floral scent bouquet. Choice experiments suggest that the species-specific odour might be responsible for the selective attraction of either wasps or bees. Furthermore, wasp-pollinated G. physocarpus flowers offer relatively large amounts of nectar that is freely accessible to insect visitors, whereas in G. fruticosus the site of nectar accumulation is covered by a specific morphological structure that makes it difficult for short-tongued insects such as wasps to access the nectar. Altogether, pollinator specialisation in the two Gomphocarpus species seem to be due to a combination of floral filter mechanisms and olfactory cues that cause flower visitors to learn to differentiate between the two species.