Pollen Load Size Research Articles

Patterns and drivers of pollen co‐transport network structure vary across pollinator functional groups

Abstract The patterns and drivers of pollen transport on insect bodies can have important consequences for plant reproductive success and floral evolution; however, they remain little studied. Recently, pollinator bodies have been further described as pollen competitive arenas, where pollen grains can compete for space, with implications for the evolution of pollen dispersal strategies and plant community assembly. However, the identity, strength, and diversity of pollen competitive interactions and how they vary across pollinator functional groups is not known. Evaluating patterns and drivers of the pollen co‐transport landscape and how these vary across different pollinator groups is central to further our understanding of floral evolution and co‐flowering community assembly. Here, we integrate information on the number and identity of pollen grains on individual insect pollen loads with network analyses to uncover novel pollen co‐transport networks and how these vary across pollinator functional groups (bees and bee flies). We further evaluate differences in pollen load size, species composition, diversity and phylogenetic diversity among insect groups and how these relate to body size and gender. Pollen co‐transport networks were diverse and highly modular in bees, with groups of pollen species interacting more often with each other on insect bodies. However, the number, identity and frequency of competitors that pollen grains encounter on insect bodies vary between some pollinator functional groups. Other aspects of pollen loads such as their size, richness and phylogenetical diversity were shaped by bee size or gender, with females carrying larger but less phylogenetically diverse pollen loads than males. Synthesis. Our results show that the number, identity and phylogenetic relatedness of pollen competitors changes as pollen grains travel on the body of different pollinators. As a result, pollinator groups impose vastly different interaction landscapes during pollen transport, with so far unknown consequences for plant reproductive success, floral evolution and community assembly.

Pollen layering and male-male competition: Quantum dots demonstrate that pollen grains compete for space on pollinators.

Almost nothing is known about what happens to pollen grains once they attach to pollinators, although some have postulated that pollen from different donors may form complex, two- or three-dimensional landscapes (e.g., layers or mosaics) that can facilitate male-male competition. For example, pollen that is already on pollinators may preclude the deposition of subsequent pollen grains. Using quantum dots to mark the pollen of individual flowers, we explored the possibilities of layering and preclusion in a fly-pollinated iris, Moraea lurida. The proportion of labeled pollen from the last flower visited diminished in sequential pollen samples taken from the top to the bottom of the pollen load, representing the first empirical evidence for pollen layering. However, the consequences in terms of pollen preclusion were equivocal: Although the pre-existing pollen load size was not a good predictor of new pollen receipt, labeled pollen loads from the last flower visited were significantly smaller than pollen loads from the previous flower visited. Thus, pollen from the previous flower may preclude pollen placement from a subsequently visited flower, and pollen from different flowers may compete for space on pollinators.

Larger pollen loads increase risk of heat stress in foraging bumblebees.

Global declines in bumblebee populations are linked to climate change, but specific mechanisms imposing thermal stress on these species are poorly known. Here we examine the potential for heat stress in workers foraging for pollen, an essential resource for colony development. Laboratory studies have shown that pollen foraging causes increased thoracic temperatures (Tth) in bees, but this effect has not been examined in bumblebees nor in real-world foraging situations. We examine the effects of increasing pollen load size on Tth of Bombus impatiens workers in the field while accounting for body size and microclimate. We found that Tth increased by 0.07°C for every milligram of pollen carried (p = 0.007), resulting in a 2°C increase across the observed range of pollen load sizes. Bees carrying pollen were predicted to have a Tth 1.7-2.2°C hotter than those without pollen, suggesting that under certain conditions, pollen loads could cause B. impatiens workers to heat from a safe Tth to one within the range of their critical thermal limits that we measured (41.3°C to 48.4°C). Bumblebees likely adopt behavioural or physiological strategies to counteract the thermal stress induced by pollen transport, and these may limit their foraging opportunities as environmental temperatures continue to increase.

Composition and Nutrition of Wild Bees in Solanum melongena L. Agroecosystems in Pune, Maharashtra, India

Eggplant, (Solanum melongena L.), also called aubergine or Guinea squash, in the nightshade family (Solanaceae) is an economically important crop in India. We investigated the significance of Solanum melongena pollen in the diet of wild bees found in agroecosystems by examining pollen on the bees using a pollen load analysis and a nutritive analysis. We selected five agricultural sites that cultivate S. melongena near Pune, Maharashtra, India. At each site, over a two-year period, we sampled the wild bees that visited mature flowers. We sampled pollen from mature flowers and also from the bodies of the bee specimens. The pollen grains from the bees were observed under a light microscope and a scanning electron microscope. They were counted using a Neubauer chamber and the pollen probability index for each bee species was calculated. The nutritive value of S. melongena pollen was estimated by extracting and characterising their proteins using liquid chromatography mass-spectrometry. Protein peptides sequences were extracted from the NCBI protein database to examine their essential amino acids. We collected 324 bees representing 11 species in three families involved in S. melongena pollination. Apis florea and A. cerana were the most abundant bees that visited S. melongena flowers. Pollen load size is highly variable ranging between few thousand to 134146 pollen grains per bee. However, the pollen probability index indicated a high degree of specificity to S. melongena pollen. S. melongena has high pollen protein content and a total of 10 different proteins were identified that are important for plant cell activities as well as the nourishment of pollinators. Further proteomic characterization of the indicated that nearly half the essential amino acids played and nutrient role in the bees. This study highlights that nutrititive composition of S. melongena pollen and highlights its potential to play a significant role in wild bee diets.

Bumble bees exploit known sources but return with partial pollen loads when foraging under low evening light

Diel activity of diurnal pollinating insects declines well before the end of day, but a few species, such as bumble bees, can continue foraging in the period before sunset, when light levels decrease. Foraging during this time could be costly for individuals, and key decisions regarding the daily cessation of foraging behaviour have to be made during this period of rapid abiotic change. However, little is known about the behaviour of diurnal bees under these light conditions. We conducted a field experiment in a mixed agricultural landscape to investigate pollen foraging in the hour before sunset in the buff-tailed bumble bee, Bombus terrestris , comparing it to an hour during the afternoon. We monitored activity at the colony entrance and collected pollen sacs from returning foragers. Overall, there were fewer exits and returns in the evening period than in the afternoon period. Evening foragers returned to the colony with partial pollen loads when compared to daytime foragers, and those returning in lower light levels had smaller loads. Additionally, we found that the same flower taxa were being exploited in the evenings as in the daytime. We found no effect of individual size on the likelihood of evening foraging or the size of pollen loads. Our results suggest that B. terrestris are facultative evening foragers that opportunistically exploit profitable flowers they have encountered during the day. Evening foragers decide to return to the colony with partial pollen loads in this period of the foraging day, which results in a largely reduced pollen influx to the colony at the end of the day. Our findings indicate that the gradual decline in light is likely to be an important factor guiding the decisions of bumble bees and other diurnal pollinators of whether to extend or end foraging, and when to return to the colony. • Bumble bees are facultative evening foragers. • Pollen foraging in the evening comes at an acquisition cost. • Light intensity is a key limiting factor for pollen collection. • Evening foragers have the same floral preferences as daytime foragers. • Individual size does not affect pollen foraging in the late evening.

Fruit Set in Avocado: Pollen Limitation, Pollen Load Size, and Selective Fruit Abortion

Avocado is a woody perennial fruit crop originating in Central America and Mexico domesticated and cultivated in the Americas since pre-Columbian times, currently cultivated in subtropical, tropical, and Mediterranean climates worldwide, with increasing importance in international trade. Avocado shows an exuberant flower production that, however, results in a very low fruit set reflected in a massive abscission of flowers and fruitlets. Several factors are involved in this behavior, and, in this work, we have focused on pollination limitation. The results obtained show that pollen deposition takes place at the female and male stages during the avocado flowering season and that the percentage of flowers with pollen on the stigma varies along the flowering season, probably due to changes in temperature that affect not only the floral behavior but also pollinator activity. However, no embryo or endosperm development took place when pollination occurred during the male flowering phase. Thus, the low number of pollen grains landing on the stigmas of female stage flowers observed under natural pollination conditions might not be enough to ensure a good yield. The production of an excess of flowers and subsequent flower drop of most of the flowers provides the opportunity of a selective fruitlet drop depending on the genotype of the embryo since fruits derived from outcrossing showed higher chances of reaching maturity. Moreover, an important competition for resources occurs among developing fruits and new vegetative growth, conferring importance to the time of flower fertilization for effective fruit set.

Comparison of the pollination efficiency of Apis cerana with wild bees in oil-seed camellia fields

Camellia oleifera Abel is an economically-important, cross-pollinated oil tree grown commercially in China. Fruit set is greatly enhanced when animal pollinators are available in this system. Prior studies have shown that bees are the primary pollinators of Camellia oleifera, but we do not know which are the most effective. This study was conducted in Xinyu, Jiangxi province, China. Through tracking observation, we measured visit duration and the tendency of bees to visit new plants, critical for the self-incompatible C. oleifera. Further, we assessed pollen loads, pollen removal rates and pollen deposition per single visit to C. oleifera, as measures of pollination efficiency for comparing the managed honey bee (A. cerana) with wild bees (C. gigas and four Andrena species). Determining the pollination efficiency of bees is important for increasing fruit set and crop yield.The managed hongeybee Apis cerana has the longest single-visit time (92.40±8.31s) with a higher visit frequency to flowers on the same tree. The difference in duration was not significant between Apis cerana and three wild bee species (A. camellia, A. hunanensis and A. striata). Conversely, the pollen deposition of A. cerana was the lowest, significantly lower than that of four species of Andrena. Further, there were significant differences in the pollen load of six species: the amount of pollens on hind legs and body surface of A. cerana was much lower than in the wild bees. Compared with the four species of Andrena, Colletes gigas moved between plants more frequently. Given its large size, it also had the highest pollen load size, pollen removal and higher deposition rates, meaning it can essentially deposit more pollen across more flowers per unit time. The efficiency of Andrena striata Wu was relatively low compared to its congeners, which were similar.

Diversity and composition of pollen loads carried by pollinators are primarily driven by insect traits, not floral community characteristics.

Flowering plants require conspecific pollen to reproduce but they often also receive heterospecific pollen, suggesting that pollinators carry mixed pollen loads. However, little is known about drivers of abundance, diversity or composition of pollen carried by pollinators. Are insect-carried pollen loads shaped by pollinator traits, or do they reflect available floral resources? We quantified pollen on 251 individual bees and 95 flies in a florally diverse community. We scored taxonomic order, sex, body size, hairiness and ecological specialization of pollinators, and recorded composition of available flowers. We used phylogenetically controlled model selection to compare relative influences of pollinator traits and floral resources on abundance, diversity and composition of insect-carried pollen. We tested congruence between composition of pollen loads and available flowers. Pollinator size, specialization and type (female bee, male bee, or fly) described pollen abundance, diversity and composition better than floral diversity. Pollen loads varied widely among insects (10-80,000,000 grains, 1-16 species). Pollen loads of male bees were smaller, but vastly more diverse than those of female bees, and equivalent in size but modestly more diverse than those of flies. Pollen load size and diversity were positively correlated with body size but negatively correlated with insect ecological specialization. These traits also drove variation in taxonomic and phylogenetic composition of insect-carried pollen loads, but composition was only weakly congruent with available floral resources. Qualities of pollinators best predict abundance and diversity of carried pollen indicating that functional composition of pollinator communities may be important to structuring heterospecific pollen transfer among plants.

Honeybee colonies provide foragers with costly fuel to promote pollen collection.

Honeybee pollen foragers departing the hive carry concentrated nectar to use as fuel for flight and glue for forming pollen loads. Since nectar is concentrated by in-hive bees at the cost of time and energy, using concentrated nectar increases the cost of foraging at the colony level. This experimental study explored the potential benefit to honeybees of using concentrated nectar for pollen collection by diluting nectar carried by pollen foragers from the hive. Mass feeding with 30% sugar solution successfully reduced the crop-load-sugar concentration in putative pollen foragers departing the hive, but while those bees tended to increase the crop-load volume, such increase did not fully compensate for the decreased amount of dissolved sugars in the crop load. Feeding 30% sugar solution reduced the pollen load dry weight by approx. 10-20% compared to the unfed control and to another test group fed 60% sugar solution. In addition, the pollen load size and sugar concentration of crop load remaining in returning pollen foragers was positively correlated. These results clearly show the advantage to honeybees of using concentrated nectar for pollen foraging.

Plant-pollinator network structural properties differentially affect pollen transfer dynamics and pollination success.

Plant-pollinator network studies have uncovered important generalities in the structure of these communities, rapidly advancing our understanding of the underlying drivers of such a structure. In spite of this, however, it is still unclear how changes in structural network properties influence overall plant pollination success. One key limitation is the lack of information on the relationship between network structural properties and aspects of pollination and plant reproductive success. Here, we estimate four plant species network structural metrics (interaction strength, weighted degree, closeness centrality, and specialization level), commonly used to describe their importance within plant-pollinator networks, at two different sites, and evaluate their effects on pollen deposition and pollen tube success. We found a positive effect of plant-pollinator specialization and a negative effect of closeness centrality on heterospecific pollen load size. We also found a marginal negative effect of closeness centrality on pollen tube success. Our results suggest that increasing plant-pollinator specialization within nested communities (pollinated by one or very few generalist insect species) may result in high levels of heterospecific pollen transfer. Furthermore, the differential effects of plant-pollinator network metrics on pollination success (pollen receipt and pollen tube success), highlight the need to integrate quantity (e.g. visitation rate) and quality (e.g. pollen delivery) aspects of pollination to achieve a more mechanistic understanding of the relationship between plant-pollinator network structure and function. Such knowledge is key to evaluate the resilience and stability of plant-pollinator communities and the services they provide in the face of increasing human disturbances.

Native honeybees as flower visitors and pollinators in wild plant communities in a biodiversity hotspot

AbstractWestern honeybees (Apis mellifera L.), native to Europe and Africa, have been transported worldwide and are now one of the most important global crop pollinator species. Although the relative contribution of honeybees to global crop pollination is increasingly recognized, relatively little is known about their importance as pollinators in wild plant communities. The only remaining wild and unmanaged western honeybee populations are in Africa. We investigated the importance of honeybees as pollinators of diverse wild plant communities in two protected areas within the Maputaland–Pondoland–Albany biodiversity hotspot in South Africa. Sites were far from any known areas of beekeeping, and so all honeybees were most likely from wild colonies. Honeybees visited a large proportion of flowering plant species within these two communities (40% and 35%) and also provided a substantial proportion of visits to the plants they visited (40% and 32%, respectively). However, when pollinator importance indices (based on abundance and the size and purity of pollen loads) were calculated for a small subset of plants, honeybees were only important pollinators of 29% of the plants they visited. Our data provide a first step in determining the importance of honeybees as flower visitors and pollinators in wild plant communities and the potential impacts of honeybee declines on these highly diverse grassland ecosystems. Our work suggests that many plants in the grassland systems studied are visited by non‐Apis flower visitors and therefore that conservation efforts should also focus on these pollinator groups.

Taxonomic and functional diversity of the co‐flowering community differentially affect Cakile edentula pollination at different spatial scales

Abstract The number of co‐flowering species, floral density and floral trait diversity can be major determinants of pollinator‐mediated plant–plant interactions in a community. However, evaluation of how each one of these co‐flowering components affects the pollination success of a single focal plant species, and how these effects vary at different spatial scales, is lacking. Here, we evaluated the effects of functional diversity (flower morphology and colour), taxonomic diversity (reflecting potential sampling effects) and flower density (conspecific and heterospecific), on the pollinator environment (i.e. visitation rate and pollinator diversity) and pollination success (i.e. pollen load size and number of pollen tubes per style) of Cakile edentula (Brassicaceae). We applied structural equation models (SEMs) at the floral‐neighbourhood (plot level) and community‐wide scales to uncover the factors that mediate co‐flowering community effects on C. edentula pollination success. We found that co‐flowering community effects at the community level are more important than fine‐scale floral‐neighbourhood differences in mediating plant pollination success in our study species. Increasing plant functional diversity decreased pollinator visitation rate but increased the diversity of pollinator functional groups visiting C. edentula flowers. Taxonomic diversity negatively affected pollinator diversity suggesting that other unmeasured floral traits may be relevant or that single‐species effects (sampling effects) may be important. Overall, our results suggest that functional floral trait diversity in a community may be the most important factor influencing pollination success of species in a community. We also found evidence for intra‐ and interspecific pollinator competition mediated by flower density, but none of these effects seemed to have a significant impact on pollination success. This study is an important step towards understanding the complexity of co‐flowering community effects on the pollination success of individual plant species at multiple spatial scales. This study further reveals the potential importance of plant functional diversity in a community in helping predict competitive and facilitative interactions in co‐flowering communities. Synthesis. Floral density and taxonomic and functional co‐flowering diversity are important drivers of pollination success in flowering plants. The effects of the co‐flowering diversity on the pollination success of plant species can largely depend on the spatial scale being studied. Only evaluating the outcomes of pollinator‐mediated plant–plant interactions at multiple stages of the pollination process can lead to a complete understanding of their ecological consequences in nature.

Variable pollen viability and effects of pollen load size on components of seed set in cultivars and feral populations of oilseed rape.

Pollination success is important for crop yield, but may be cultivar dependent. Less is known about which floral traits influence pollination success. Floral traits, e.g. traits related to attraction and reward, can also contribute to gene flow via pollen, the latter being of particular importance in oilseed rape (Brassica napus) where gene flow occurs between plants of crop, volunteer and feral origin as well as related taxa. We investigated the relationship between pollen load size and seed set in winter oilseed rape. We compared variability in pollen-viability traits, flower production (flowers from the main raceme times number of branches) and seed number and weight per siliqua among cultivars and feral populations (growing outside of agricultural fields) under controlled conditions. Both seed number and weight were saturated at relatively low pollen loads in the tested cultivar. Pollen viability and estimated flower production differed among cultivars, indicating that these traits could contribute to yield variability. Seed weight per siliqua, but not pollen traits or flower production, was lower in ferals compared to cultivars. Thus, while the probability of establishment may be reduced in ferals (due to lower seed weight per siliqua) this will not necessarily impact their contribution to gene flow via pollen. In oilseed rape a relatively low pollen load may be sufficient for full seed set in some cultivars, suggesting less dependence on insect pollination for high yield than generally expected. Our results also showed that previously less investigated floral traits, such as pollen viability, pollen tube growth rate and flower number, can differ between cultivars. Studies of these traits may provide targets for increasing crop yield and provide general knowledge about gene flow between cultivated, feral and related wild populations.

Venus Flytrap Rarely Traps Its Pollinators.

Because carnivorous plants rely on arthropods as pollinators and prey, they risk consuming would-be mutualists. We examined this potential conflict in the Venus flytrap (Dionaea muscipula), whose pollinators were previously unknown. Diverse arthropods from two classes and nine orders visited flowers; 56% of visitors carried D. muscipula pollen, often mixed with pollen of coflowering species. Within this diverse, generalized community, certain bee and beetle species appear to be the most important pollinators, on the basis of their abundance, pollen load size, and pollen fidelity. Dionaea muscipula prey spanned four invertebrate classes and 11 orders; spiders, beetles, and ants were most common. At the family and species levels, few taxa were shared between traps and flowers, yielding a near-zero value of niche overlap for these potentially competing structures. Spatial separation of traps and flowers may contribute to partitioning the invertebrate community between nutritional and reproductive functions in D. muscipula.

Stigma Sensitivity and the Duration of Temporary Closure Are Affected by Pollinator Identity in Mazus miquelii (Phrymaceae), a Species with Bilobed Stigma.

A sensitive bilobed stigma is thought to assure reproduction, avoid selfing and promote outcrossing. In addition, it may also play a role in pollinator selection since only pollinators with the appropriate body size can trigger this mechanism. However, no experimental study has investigated how the sensitive stigma responds to different pollinators and its potential effects on pollination. Mazus miquelii (Phrymaceae), a plant with a bilobed stigma was studied to investigate the relationship between stigma behaviors and its multiple insect pollinators. The reaction time of stigma closure after touched, duration of temporary closure, and factors determining permanent closure of the stigma were studied when flowers were exposed to different visitors and conducted with hand pollination. Manual stimulation was also used to detect the potential differences in stigmas when touched with different degrees of external forces. Results indicated that, compared to pollinators with a small body size, larger pollinators transferred more pollen grains to the stigma, causing a rapid stigma response and resulting in a higher percentage of permanent closures. Duration of temporary closure was negatively correlated with the speed of stigma closure; a stigma that closed more rapidly reopened more slowly. Manual stimulation showed that reaction time of stigma closure was likely a response to external mechanical forces. Hand pollination treatments revealed that the permanent closure of a stigma was determined by the size of stigmatic pollen load. For large pollinators, the speedy reaction of the stigma might help to reduce pollen loss, enhance pollen germination and avoid obstructing pollen export. Stigmas showed low sensitivity when touched by inferior pollinators, which may have increased the possibility of pollen deposition by subsequent visits. Therefore, the stigma behavior in M. miquelii is likely a mechanism of pollinator selection to maximize pollination success.

Patterns and sources of variation in pollen deposition and pollen tube formation in flowers of the endemic monoecious shrub Cnidoscolus souzae (Euphorbiaceae).

Pollen deposition and pollen tube formation are key components of angiosperm reproduction but intraspecific variation in these has rarely been quantified. Documenting and partitioning (populations, plants and flowers) natural variation in these two aspects of plant reproduction can help uncover spatial mosaics of reproductive success and underlying causes. In this study, we assess variation in pollen deposition and pollen tube formation for the endemic monoecious shrub Cnidoscolus souzae throughout its distribution range in Mexico, and determine how this variation is structured among populations, plants and flowers. We also infer the relative importance of pollen quantity and quality in determining pollination success in this species. While we found no evidence suggesting that pollen receipt limits C.souzae reproduction across 19 populations, we did find extensive variation in pollen load size and pollen tube number per flower. Total variation in pollen receipt and pollen tube number was mostly explained by intra-individual and among-population variance. Furthermore, pollen load size had a stronger effect on the number of pollen tubes at the base of the style than pollen germination rate, suggesting that pollen quantity may be more important than quality for pollen tube success in C.souzae. Our results suggest that both small within-plant flower differences and broad-scale differences in community attributes can play an important role in determining pollination success. We emphasise the need to evaluate patterns and sources of variation in pollen deposition and pollen tube formation as a first step in understanding the causes of variation in pollination success over broad spatial scales.

Heterospecific pollen deposition in Delphinium barbeyi: linking stigmatic pollen loads to reproductive output in the field.

Most pollinators are generalists and therefore are likely to transfer heterospecific pollen among co-flowering plants. Most work on the impacts of heterospecific pollen deposition on plant fecundity has utilized hand-pollination experiments in greenhouse settings, and we continue to know very little about the reproductive effects of heterospecific pollen in field settings. We explored how patterns of naturally deposited heterospecific pollen relate to the reproductive output of Delphinium barbeyi, a common subalpine perennial herb in the Rocky Mountains (USA). We assessed a wide range of naturally occurring heterospecific pollen proportions and pollen load sizes, and linked stigmatic pollen deposition directly to seed set in individual carpels in the field. We found that heterospecific pollen deposition in D. barbeyi is common, but typically found at low levels across stigmas collected in our sites. Neither conspecific nor heterospecific pollen deposition was related to carpel abortion. By contrast, we saw a significant positive relationship between conspecific pollen amount and viable seed production, as well as a significant negative interaction between the effects of conspecific pollen and heterospecific pollen amount, whereby the effect of conspecific pollen on viable seed production became weaker with greater heterospecific deposition on stigmas. To our knowledge, this is the first demonstration of a relationship between heterospecific pollen and seed production in a field setting. In addition, it is the first report of an interaction between conspecific and heterospecific pollen quantities on seed production. These findings, taken with the results from other studies, suggest that greenhouse hand-pollination studies and field studies should be more tightly integrated in future work to better understand how heterospecific pollen transfer can be detrimental for plant reproduction.

Adjustment of honey load by honeybee pollen foragers departing from the hive: the effect of pollen load size

Honeybee foragers load a small amount of honey into the crop when they leave the hive. This “honey at departure” is used as a material to build pollen loads (glue honey) as well as fuel during flight in pollen foragers. We investigated the relationship between the size of pollen loads that a forager collected and the amount of honey at departure in the Western honeybee, Apis mellifera. Dancing pollen foragers increased honey at departure with the size of collected pollen loads. Analysis of the waggle-run duration revealed that the size of pollen load affected the rate of increase of honey at departure with food source distance in dancers. The increase rate was significantly higher in dancers that had returned to the hive with large pollen loads versus nectar-collecting dancers, but not in those with smaller pollen loads. The higher increase rate may reflect additional fuel carried for the return trip in pollen-foraging specialists that do not use collected nectar as fuel. Although honey carried by departing dance followers also increased significantly with the size of pollen load carried by dancers, the adjustment was different from that of dancers. These results suggest that recruited bees adjust the amount of honey at departure, including glue honey, based on communicated information and modify the amount of honey load subsequently based on their own experience.

Influence of the Collection Season on Production, Size, and Chemical Composition of Bee Pollen Produced by Apis Mellifera L.

Abstract The aim of our study was to investigate how the collection period affects and influences the production, chemical composition, and size of bee pollen loads (0.5, 1.0, 2.0, greater than 2.0 mm). The results showed there was a predominance of pollen loads with a diameter greater than 2.0 mm in all the production seasons. For all the seasons, there were no differences in protein content between the particle sizes. But when comparing 0.5 mm during the different periods, there were significant differences; the highest value was found during the winter (24.39 ± 3.7%). As far as lipids and crude fiber are concerned, we obtained differences between the same granulometry sizes for the spring and summer seasons. As for ashes, the results showed differences between different particle sizes for the summer and autumn seasons. Our results have shown that regardless of pollen particle size, its quality was not altered, suggesting that smaller loads can be commercially used by containing nutritional quality or else be used by beekeepers as a supplement during periods of food scarcity.

Pollen Viability and the Potential for Self-Pollen Interference inPhlox hirsuta, an Endangered Species

Premise of research. Hermaphroditic plants with self-incompatible mating systems often produce flowers that fail to mature seed-containing fruits. A variety of factors can affect reproductive success in these species, including pollen load size, pollen viability, pollen-pistil compatibility, and self-pollen interference. We combined field, growth chamber, and laboratory studies to identify factors that are and are not responsible for high ovule-to-seed ratios in Phlox hirsuta, a self-sterile, hermaphroditic, endangered species.Methodology. We (1) determined whether pollen load size affected seed set by counting the number of grains on stigmas following natural pollinations and following outcross-only pollinations, (2) assessed pollen viability by staining grains collected from flowers of different ages, (3) quantified the degree of autonomous self-pollination by counting the number of self-pollen grains that accumulated on stigmas over time, and (4) determined whether self pollen on stigmas interfered wit...