Pollen Shortage Research Articles

Evaluation of Some Pollen Substitutes on Productivity of Honey bee Colonies (Apis cerana F.)

This study examined the effects of different pollen substitutes on the performance of honey bee colonies in Assam, India. Natural Corbicula pollen (CPF) and six artificial diets were compared with a sugar syrup control for 15 days. CPF consistently outperformed other treatments in all parameters. Regarding the honey area, the CPF reached 22.63 cm2 and 22.65 cm2 in 2021 and 2022, respectively, while in the control group it was 15.61 cm2 and 15.72 cm2, respectively. CPF also had the highest pollen area (15.59 cm² and 15.68 cm²) and brood area (20.19 cm² and 20.35 cm²) in both years. Colony strength was maximized in the CPF (7.55 and 7.59 for frames 2021 and 2022). Among artificial foods, OUAT-PS (soy flour, honey, yeast, multivitamin) generally performed best, with no significant difference from CPF in colony strength. All pollen substitutes stimulated honey production and brood development with foods rich in proteins, vitamins and amino acids, and significantly improved colony performance compared to controls. These results can help beekeepers select appropriate additional nutrients in times of pollen shortage.

Flight performance of pollen starved honey bees and incomplete compensation through ingestion after early life pollen deprivation.

We investigated the effect of adult honey bee pollen nutrition on the flight performance of honey bees. Therefore, caged bees were allowed to perform 30min of defecation/training flights every second day before flight performance of pollen-fed bees and pollen-deprived bees older than 16days were compared in a flight mill. We first fed 10µL of 1M glucose solution to bees, and after they metabolized this during flight, they were fed 10µL of 2M glucose solution for a second flight test. Pollen-deprived bees flew longer and further than pollen-fed bees in both flights. Pollen-fed bees flew faster in the early period at the beginning of flights, whereas pollen-deprived bees were faster in the final phases. Pollen-fed bees were able to raise their maximum flight speed in 2M glucose solution flights, whereas pollen-constraint bees were not. The two groups did not differ in abdomen fresh weight, but the fresh weight of the head and thorax and dry weight of the head, thorax and abdomen were higher in pollen-fed bees. In a second experiment, we constrained pollen consumption of caged bees during the first 7days and compared daily consumption of bees from day 8-16 to consumption of bees unrestricted in pollen. We found that pollen-deprived bees perceive the pollen shortage and try to compensate for their needs by consuming significantly more pollen at the later phase of their life than pollen-fed bees of the same age. Still, bees constrained from pollen in the first 7days did only reach 51.1% of the lifetime consumption of unconstrained bees. This shows that bees can sense the need for essential nutrients from pollen, but their physiological apparatus does not allow them to fully compensate for their early life constraint. Pollen deprivation only in the first 7days of worker life likewise significantly reduced fresh and dry weights of the body sections (head, thorax, and abdomen) and survival. This underlines the importance of protein consumption in a short critical period early in adult bees' lives for their development and their performance later in life.

Diversity, floral phenology, and socio-economic importance of melliferous plants in Eastern Ethiopia

Abstract. Fassil A, Habtamu T, Tahir M, Terefe T. 2022. Diversity, floral phenology, and socio-economic importance of melliferous plants in Eastern Ethiopia. Nusantara Bioscience 14: 172-181. Beekeeping is a supply of extra money and financial gain for many thousands of farmer beekeepers in Ethiopia and plays a big role in preserving natural resources. Honeybees and flowering plants have co-evolved in their special symbiotic relationship. Bee plant types and their flowering duration differ from one place to another due to variations in topography, climate, and other cultural and farming practices. This study investigated and documented the diversity and floral phenology of honeybee plants in Doba, Gemechis, and Mi’eso Districts, Oromia National Regional State, Eastern Ethiopia, from January 2019 to July 2021. Ethnobotanical data were collected to reveal the diversity of melliferous plants, practices, and communities’ attitudes about honey production and melliferous plant conservation. A total of 422 respondents participated through semi-structured interviews, focus group discussions, and field walks for socio-economic data collection. Descriptive statistics such as frequencies, ranking, and scores were used and presented with tables and figures to analyze ethnobotanical data. A total of 120 melliferous plant species were distributed under 108 genera and 55 families, of which 70 plants were found in the Gemechis District, followed by Doba and Mi’eso Districts with 47 and 42 plants each, respectively. Sorenson’s Similarity Index values showed the wide-ranging melliferous plant species distribution patterns in the three districts with 50.4 (between Doba and Mi’eso), 37.5 (between Doba and Gemechis), and 15.3 (between Gemechis and Mi’eso) species overlaps. Fabaceae and Asteraceae contribute a significant number of species, with 12 (10 %) and 9 (7.5 %) melliferous plants, respectively. Local communities have a good awareness of the seasonal availability of melliferous plants, indicating adequate supply (June to early December) and critical shortage (November to early May) of melliferous plant resources favoring strong and weak colony strength, respectively. Lack of nutrition, improper management practices, honey bee predators, and lack of beekeeping knowledge and equipment were the most important constraints deleteriously influencing the honey quality and amount in the study area. The shortage of pollen and nectar flow during the dearth periods (January to March) needs interventions like hive migration and bee floral plantations. Hence, there is an urgent need for intervention through awareness creation, campaign-based melliferous plant plantations, and technology transfers.

Inter-varietal sterility and fertility restoration in Oryza sativa Linn.

This study explored the underlining reproductive factors that cause sterility in rice, using hybrids obtained from crosses among landrace selections and improved varieties. The study was carried out between 2016 and 2018. Nine landrace cultivars and two improved varieties were involved in the hybridization experiment. Among the 17 putative hybrids that were obtained, only 5 were confirmed as true hybrids. Meiotic chromosome studies and pollen studies in the F1, and Mendelian segregation studies for fertility in the F2 were carried out. Some F2 lines were monitored to F3 to ascertain the level of fixation of gene combinations for fertility. The results obtained from the chromosomal studies showed that phenomena such as laggards, precocious movements, formation of multivalents, and unequal segregation to the poles are associated with pollen sterility in all - 5 hybrids, at the F1 and F2 generations. The indehiscence of anthers contributed to infertility due to pollen shortage than the fertility of the pollens themselves. Even though in males, there is a preponderance of male sterility, female sterility is also a phenomenon that is possibly contributing to inter-varietal sterility. The segregational pattern of 13:3 was observed for fertility in the F2 which suggests the inhibition of fertility by a gene in the dominant state. There was the restoration of fertility in many of the lines advanced to the F3 to up to 93 % fertility. It was, therefore, concluded from the study that landraces of rice still hold the key for the rice crop improvement and should therefore be conserved.

Nutritional benefit of fungal spores for honey bee workers

The collection of fungal spores by honey bees, Apis mellifera, can be classified as active or passive, the latter when spores are associated with pollen, nectar or honey dew. While low quality and shortage of pollen have been raised as hypotheses for fungal spore collection, the nutritional value of fungal spores for honey bees is poorly understood. Here we investigated the effect of consumption of fungal spores on survival, ovarian activation and the development of the hypopharyngeal glands (HPGs) in honey bee workers. Two pollen diets (Eucalyptus sp. pollen and a multifloral pollen) supplemented or not with spores of Botrytis cinerea, Cladosporium sp. or Colletotrichum acutatum were used. Consumption of diets that contained fungal spores increased the longevity of honey bee workers but had no significant effect on the development of their HPGs and ovaries. This demonstrates that fungal spores may have nutritional value for honey bees and that the consumption of fungal spores may compensate for nutritional imbalances of poor-quality pollen diets.

Bumble bees damage plant leaves and accelerate flower production when pollen is scarce.

Maintaining phenological synchrony with flowers is a key ecological challenge for pollinators that may be exacerbated by ongoing environmental change. Here, we show that bumble bee workers facing pollen scarcity damage leaves of flowerless plants and thereby accelerate flower production. Laboratory studies revealed that leaf-damaging behavior is strongly influenced by pollen availability and that bee-damaged plants flower significantly earlier than undamaged or mechanically damaged controls. Subsequent outdoor experiments showed that the intensity of damage inflicted varies with local flower availability; furthermore, workers from wild colonies of two additional bumble bee species were also observed to damage plant leaves. These findings elucidate a feature of bumble bee worker behavior that can influence the local availability of floral resources.

Bumble bee gardeners

Pollinators Bumble bees rely heavily on pollen resources for essential nutrients as they build their summer colonies. Therefore, we might expect that annual differences in the availability of these resources must simply be tolerated, but Pashalidou et al. made observations suggesting that bees may have strategies to cope with irregular seasonal flowering (see the Perspective by Chittka). When faced with a shortage of pollen, bumble bees actively damaged plant leaves in a characteristic way, and this behavior resulted in earlier flowering by as much as 30 days. Experimenters were not able to fully replicate the results with their own damage, suggesting that there is a distinct method that the bees use to stimulate earlier flowering. Science , this issue p. [881][1]; see also p. [824][2] [1]: /lookup/doi/10.1126/science.aay0496 [2]: /lookup/doi/10.1126/science.abc2451

Honey Bee (Hymenoptera: Apidea) Pollen Forage in a Highly Cultivated Agroecosystem: Limited Diet Diversity and Its Relationship to Virus Resistance

Intensified agriculture reduces natural and seminatural habitats and plant diversity, reducing forage available to honey bees (Apis mellifera L. [Hymenoptera: Apidea]). In agricultural landscapes of Iowa, United States, we studied the impact of extrinsic agricultural intensification on the availability of pollen for honey bees by placing colonies next to soybean fields surrounded by either a low or high level of cultivation. The abundance and diversity of pollen returned to a colony were estimated by placing pollen traps on bee colonies during the summer and fall of 2015 and 2016. We observed no difference in abundance and diversity of pollen collected by colonies in either landscape, but abundance varied over time with significantly less collected in September. We explored if the most commonly collected pollen from these landscapes had the capacity to support honey bee immune health by testing if diets consisting of these pollens improved bee resistance to a viral infection. Compared to bees denied pollen, a mixture of pollen from the two most common plant taxa (Trifolium spp. L. [Fabales: Fabaceae] and Chimaechrista fasciculata (Michx.) Greene [Fabales: Fabaceae]) significantly reduced honey bee mortality induced by viral infection. These data suggest that a community of a few common plants was favored by honey bees, and when available, could be valuable for reducing mortality from a viral infection. Our data suggest a late season shortage of pollen may be ameliorated by additions of fall flowering plants, like goldenrod (Solidago spp. L. [Asterales: Asteraceae]) and sunflower (Helianthus, Heliopsis, and Silphium spp. [Asterales: Asteraceae]), as options for enhancing pollen availability and quality for honey bees in agricultural landscapes.

The carry‐over effects of pollen shortage decrease the survival of honeybee colonies in farmlands

Summary Many studies have reported honeybee colony losses in human‐dominated landscapes. While bee floral food resources have been drastically reduced over past decades in human‐dominated landscapes, no field study has yet been undertaken to determine whether there is a carry‐over effect between seasonal disruption in floral resource availability and high colony losses. We investigated if a decline in the harvest of pollen by honeybees in spring affected managed honeybee colony dynamics (brood size, adult population and honey reserves) and health (Varroa mite loads and colony survival) throughout the beekeeping season. A decline in pollen harvest was associated with a direct reduction in brood production, leading to a negative effect on the adult population size later in the season, and lower honey reserves before the onset of winter. Furthermore, the decline in pollen harvest negatively impacted the health of the colony, resulting in higher Varroa mite loads and higher seasonal and winter colony losses. Early‐warning signs of these carry‐over effects were identified, showing that preferential investment in honey reserves instead of brood production early in the season increased the decline in pollen harvest and its associated carry‐over effects. Synthesis and applications. The results suggest that the decline in pollen harvest may have been overlooked as a cause of pollen shortage and associated bee colony losses. Strategies to avoid such losses in intensive farmland systems include (i) limiting or avoiding honey harvests in spring, (ii) monitoring colonies for early‐warning signals of colony failure and (iii) increasing the amount of floral resources available through wise land‐use management.

Nectar accessibility determines fitness, flower choice and abundance of hoverflies that provide natural pest control

Summary In modern agricultural landscapes, many organisms providing ecosystem services such as pollination and natural pest control are likely constrained by shortage of nectar and/or pollen required for adult nutrition. More and more flower‐rich field margin strips and other habitats are created to eliminate these constraints. For most target organisms, however, it is not well known which (types of) flowers are effective in providing suitable pollen and nectar. We studied the suitability of a wide range of flowers as a food source for zoophagous hoverflies (hoverflies with predatory larvae) at five different levels: nectar accessibility (based on flower morphology), realized adult fitness, flower choice (both based on cage experiments), flower visitation and hoverfly abundance in mixed vegetation (both based on field observations). Realized survival of Episyrphus balteatus is related to effective flower depth by a sigmoid function. The critical flower depth is 1·6 mm, which is less than the proboscis size of the hoverfly. For Asteraceae, the critical floret depth is even less than 1·0 mm, which – in contrast to common knowledge – rules out most species within this family. Both flower choice in the laboratory and flower visitation rates in the field are well correlated with nectar accessibility and realized adult survival. In mixed floral vegetation, the number of zoophagous hoverflies is highly correlated with the abundance of only those flowers that have accessible nectar for these hoverflies. Synthesis and applications. This comparative study demonstrates that nectar (and not pollen) accessibility is the main driver determining flower resource suitability, flower choice and abundance of zoophagous hoverflies in arable field margins. The study identifies the limited range of plant species that can effectively support these beneficial insects. Preserving the right flowers in and around agricultural fields could enhance local populations and the pest control and pollination services they provide.

Reproductive consequences of mate quantity versus mate diversity in a wind-pollinated plant

Since most pollen travels limited distances in wind-pollinated plants, both the local quantity and diversity of mates may limit female reproductive success. Yet little evidence exists on their relative contribution, despite the importance of viable seed production to population dynamics. To study how variation in female reproductive success is affected by the quantity versus the diversity of surrounding mates contributing pollen, we integrated pollination experiments, data on natural seed set and seed viability, and AFLP genetic marker data in the wind-pollinated dioecious clonal forest herb Mercurialis perennis. Pollination experiments indicated weak quantitative pollen limitation effects on seed set. Among-population crosses showed reduced seed viability, suggesting outbreeding depression due to genetic divergence. Pollination with pollen from a single source did not negatively affect reproductive success. These findings were consistent with results of the survey of natural female reproductive success. Seed set decreased with the distance to males in a female plants’ local neighborhood, suggesting a shortage of pollen in isolated female plants, and increased with the degree of local genetic diversity. Spatial isolation to other populations and population size did not affect seed set. None of these variables were related to seed viability. We conclude that pollen movement in M. perennis is likely very limited. Both male proximity and the local degree of genetic diversity influenced female reproductive success.

Effect of pollination on seed set of Origanum syriacum under semiarid Mediterranean conditions

This study was aimed at identifying the potential different insect visitors of Origanum syriacum flowers and at evaluating their role in seed set in Syrian Oregano grown under its native semiarid Mediterranean conditions. Three treatments were imposed on O. syriacum plants before flowering: 1) Plants were left uncovered to permit insect visiting, 2) plants were covered and hand pollinated with pollen from flowers of other plants, and 3) plants were covered (control). The results showed that 21 bee species were identified visiting O. syriacum flowers, of which 8 species were recorded for the first time in Jordan. Supplementary pollination produced a higher significant number of seeds and seed set than other pollination treatments that led us to conclude that O. syriacum flowers are affected by pollen shortage under natural conditions. Wind plays little or no role in its pollination process. There is low seed yield production and seed set by O. syriacum under natural conditions in Jordan. The number of bee colonies as well as the wild bees must be enhanced in the area to improve their value in O. syriacum flower pollination.

The effect of surface area of pollen patties fed to honey bee (Apis mellifera) colonies on their consumption, brood production and honey yields

SummaryBeekeepers may feed colonies with pollen supplement patties during times of pollen shortage. We tested whether the surface area of pollen patties fed to honey bee colonies affects their consumption, brood production and honey yields. We compared three pollen-patty sizes, of equal weight, and found that consumption increased with surface area. Consequently, brood production tended to increase with pollen-patty size, and colonies fed the patty with the largest surface area produced significantly more brood than those fed a carbohydrate-only control patty. The colonies in the large surface area treatment also tended to produce more honey, though the differences were not statistically significant, probably due to the time gap between the pollen deficiency period and the time honey was harvested. We conclude that pollen patties with greater surface area are more readily consumed by honey bee colonies and may contribute more to colony development and subsequent honey yields.

Reduced seed production, inbreeding, and pollen shortage in a small population of a threatened tree, Magnolia stellata

We investigated how genetic factors and pollen shortage affect seed production in a small population of Magnolia stellata, a threatened insect-pollinated tree. We used microsatellite and manual pollination techniques, and compared a small population to a large one. Compared to the large population, the small population showed low allelic variation and had an F IS significantly greater than 0 in adults, indicating that genetic deterioration, including genetic drift and inbreeding, may have occurred in adults. Manual self-pollination lowered seed production relative to manual cross-pollination to a different extent between populations: δ (the magnitude of inbreeding depression due to self-fertilization) was lower in the small population than in the large population. However, under natural pollination, the estimated embryo mortality rates after ovules self-fertilized were similar between the two populations because the primary selfing rate was higher in the small population. The ovule mortality rate due to pollen shortage and that due to factors independent of pollen shortage and selfing were both approximately 10% higher in the small population, suggesting that pollen transfer may have decreased and genetic deterioration effects may have increased in that population. These factors reduced seed production in the small population (female reproductive success = 0.3%) compared to the large population (2.6%). Our results suggest that seed production in the small population of M. stellata is strictly limited by elevated pollen shortage, selfing, and genetic deterioration in adults, which accelerate the risk of extinction.

Space mediates coexistence of females and hermaphrodites

In gynodioecious populations of flowering plants females and hermaphrodites coexist. Gynodioecy is widespread and occurs in both asexual and sexual species but does not admit a satisfactory explanation from classical sex ratio theory. In sexual populations male fertility restoring genes have evolved to counter non-nuclear male sterility mutations. In pseudogamous asexual populations pollen retention and increased self-fertilization can make male sterility costly. Both of these mechanisms can promote coexistence. However, it remains unclear how either of these mechanisms could evolve if coexistence was not initially possible. In the absence of these adaptations non-spatial models predict that females either fail to invade hermaphrodite populations or else displace them until pollen shortage drives the population to extinction. We develop a pair approximation to a probabilistic cellular automata model in which females and hermaphrodites interact on a regular lattice. The model features independent pollination and colonization processes which take place on different timescales. The timescale separation is exploited to obtain, with perturbation methods, a more manageable aggregated pair approximation. We present both the mean field model which recreates the classical non-spatial predictions and the pair approximation, which strikingly predicts different invasion criteria and coexistence under a wide range of parameters. The pair approximation is shown to correspond well qualitatively with simulation behaviour.

Pollen Collection and Brood Production by Honeybees (<i>Apis mellifera</i> L.) under Chitwan Condition of Nepal

A study was carried out to investigate pollen foraging, storage and its impact on Apis mellifera L brood production throughout the year under Terai condition of Nepal in 2003-2005. Number of pollen foragers, amount of pollen stored as beebread and brood in the colony differed significantly during different seasons. Number of pollen foragers (117.5 bees/ hive/ 5 min) and amount of pollen as beebread (2439.0 gm/hive) and number of brood (14787.2 brood cells/hive) were the highest during spring season, while the lowest number of pollen foragers (38.1 bees/ hive/5 min.) stored the lowest amount of beebread or pollen store (152.5 gm /hive) and produced the lowest number of brood (3811.7 brood cells/ hive) and bees in rainy season. Autumn, winter and summer seasons were normal for pollen collection and brood production, while starvation and nutritional deficiencies due to the acute shortage of pollen in rainy season was the major reason to decline or collapse the bee population before the honey flow season. Therefore, feeding bees with adequate amount of nutritionally rich pollen during rainy season is essential to maintain a healthy and strong bee colony for the production of higher honey and other hive products. 
 
 Key words: Honeybees, foraging, pollen, brood, Apis mellifera 
 
 J. Inst. Agric. Anim. Sci. 26: 143-148 (2005)

Effects of pollen shortage and self-pollination on seed production of an endangered tree, Magnolia stellata

Pollen limitation is a significant determinant of seed production, and can result from both insufficient pollen quantity (pollen shortage) and quality (mainly relating to self-pollination). For animal-pollinated tree species with large floral displays, pollen limitation may be determined by a balance between increased pollen quantity due to increased attractiveness for pollinators, countered by increased self-pollination due to increased geitonogamy. The contributions of pollen shortage and self-pollination on seed production were quantitatively examined in the natural pollination of an insect-pollinated, dichogamous, endangered tree, Magnolia stellata, which has a large, showy floral display. Manual self- and cross-pollinations were conducted to determine the effects of selfing on seed production. The outcrossing rate was measured using microsatellite analyses of open-pollinated seeds, and the embryo mortality rate caused by self-pollination was indirectly estimated. The frequency of ovule mortality due to pollen shortage was also inferred using the embryo mortality and ovule survival rates from natural pollination. The average fruit set, seed set per fruit, and ovule survival rate per tree from hand cross-pollination were 1.37, 3.15, and 3.34 times higher than those from hand self-pollination, respectively, indicating that self-pollination causes inbreeding depression for fruit and seed set. The multilocus-outcrossing rate (t(m)) was intermediate, 0.632, and the primary selfing rate was 0.657. This indicates that frequent geitonogamous selfing occurs. The ovule mortality rate due to pollen shortage and the embryo mortality rate due to self-pollination were estimated to be 80.8 % and 45.9 %, respectively. It is concluded that seed production of M. stellata is strongly limited by both pollen shortage and self-pollination. Inefficient beetle-pollination and the automimicry system via asynchronous flowering might be responsible for the high level of pollen shortage and frequent geitonogamy. This is despite a large, showy floral display and the dichogamous system of the species.

シデコブシの小集団化が近親交配と近交弱勢、花粉不足に与える影響 -集団サイズの異なる二集団での比較-

シデコブシの小集団化が近親交配と近交弱勢、花粉不足に与える影響 -集団サイズの異なる二集団での比較-

Sex choice in plants: facultative adjustment of the sex ratio in the perennial herb Begonia gracilis.

Sex allocation theory predicts that reproducing individuals will increase their fitness by facultatively adjusting their relative investment towards the rarer sex in response to population shifts in operational sex ratio (OSR). The evolution of facultative manipulation of sex ratio depends on the ability of the parents to track the conditions favouring skewed sex allocation and on the mechanism controlling sex allocation. In animals, which have well-developed sensorial mechanisms, facultative adjustment of sex ratios has been demonstrated on many occasions. In this paper, we show that plants have mechanisms that allow them to evaluate the population OSR. We simulated three different conditions of population OSR by manipulating the amount of pollen received by the female flowers of a monoecious herb, and examined the effect of this treatment on the allocation to male vs. female flowers. A shortage of pollen on the stigmas resulted in a more male-skewed sex allocation, whereas plants that experienced a relatively pollen rich environment tended to produce a more female-skewed sex allocation pattern. Our results for Begonia gracilis demonstrate that the individuals of this species are able to respond to the levels of pollination intensity experienced by their female flowers and adjust their patterns of sex allocation in accordance to the expectations of sex allocation theory.

Effects of Geitonogamy on the Seed Set of Magnolia obovata Thunb. (Magnoliaceae)

The effects of geitonogamy on the seed set of a protogynous hermaphroditic tree, Magnolia obovata Thunb., were investigated by electrophoretic allozyme analysis and pollination experiments. The multilocus outcrossing rates (tm) estimated in 1995 and 1997 by using four polymorphic loci were 0.39 and 0.42, respectively, indicating that more than half of the seeds are produced by geitonogamous selfing. Manual pollination demonstrated that the follicle set per fruit (frequency of ripe carpels) and seed set per fruit from self‐pollination were 2.6 and 3.8 times less than those from cross‐pollination, respectively, and the frequency of aborted seeds from self‐pollination was significantly higher than that from cross‐pollination. There was no significant difference between self‐ and cross‐pollination in the fruit set and the frequency of remnant ovules (ovules unfertilized or aborted before endosperm development). These results indicate that inbreeding depression is a primary factor reducing the seed set of self‐pollinated fruits. The fruit set, follicle set per tree, and seed set per tree from natural pollination were significantly lower than those from the manual pollinations. From these results, we estimated that 91% of ovules in M. obovata were not fertilized owing to pollen shortage, and 65% of embryos failed to develop because of geitonogamous selfing. The high embryo mortality rate from geitonogamy in M. obovata can be regarded as a cost of this tree’s pollination system, which is based on automimicry via asynchronous flowering.