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\"This title takes readers through our warming world where bee habitats are dwindling. Learn why humans are the cause of dropping bee populations and what we can do to help them bounce back\"--Publisher.
Book
Relationships of Bees to Host Ornamental and Weedy Flowers in Urban Northwest Guanacaste Province, Costa Rica
Ecological studies on native bees in urban tropical environments are rare, however, ever-increasing urban areas world-wide necessitate study on how many of these bees can and have adjusted to human constructs. Predictable ecological patterns that emerge from these studies can provide guidance on how future urban constructs can be designed to provide habitat for conserving and protecting native bees. These patterns can also be used for bee habitat restoration in natural and agricultural environments. An extensive survey of native bees and honey bees and their relationships to a community of 102 plant types in urban residential environments of Bagaces and Liberia in northwestern Costa Rica was conducted from 2003–2012. Bees were attracted and recorded at measurable frequencies to 82 plant genera in 41 families, the most common of which was Fabaceae. Forty-two plant types were native ornamentals; 39 were non-natives; and 21 were native weed species. Standardized bee visitation (frequency) counts, 17,000+, were used to record relationships between bees and flowers. The following data were recorded for each plant type: flowering phenology in months, type of floral reward(s) (pollen, nectar, and/or oil), main daily attraction period, and most frequently visiting bee taxa. Plant life forms included trees, shrubs, lianas/vines, herbs, and palms. Each plant group had a different seasonal flowering phenology with native ornamentals and native weeds having patterns that closely resembled the general patterns for wild plants in the dry forest. Predictable associations of certain bee taxa with each plant type emerged from the count data, which allowed for categorizing relationships into four types: small bee, diverse bee, specialized bee, and nocturnal pollination systems. Intraspecific variations in bee attraction to several plant types were also noted. Honey bees (Africanized) did not figure prominently in most pollination relationships, especially with regard to native plants. Most native bee species were generalized foragers. Beyond the urban environment, it is suggested that knowledge of predictable bee-flower relationships can also be used to restore bee habitat in disturbed environments such as deforested areas. With some imagination and outreach education, bee habitats could also be installed for some agricultural crops. Outreaching information on native bee-flower relationships at local, regional, and state levels is important for short and long-term propagation of urban (and agricultural) plants. Yet, very few outlets for transferring this knowledge currently exist in Costa Rica. A few limited options for sharing this information are discussed, including collaborative partnerships with local NGOs.
Journal Article
Mimicking orchids lure bees from afar with exaggerated ultraviolet signals
Flowers have many traits to appeal to pollinators, including ultraviolet (UV) absorbing markings, which are well‐known for attracting bees at close proximity (e.g., <1 m). While striking UV signals have been thought to attract pollinators also from far away, if these signals impact the plant pollinia removal over distance remains unknown. Here, we report the case of the Australian orchid Diuris brumalis, a nonrewarding species, pollinated by bees via mimicry of the rewarding pea plant Daviesia decurrens. When distant from the pea plant, Diuris was hypothesized to enhance pollinator attraction by exaggeratedly mimicking the floral ultraviolet (UV) reflecting patterns of its model. By experimentally modulating floral UV reflectance with a UV screening solution, we quantified the orchid pollinia removal at a variable distance from the model pea plants. We demonstrate that the deceptive orchid Diuris attracts bee pollinators by emphasizing the visual stimuli, which mimic the floral UV signaling of the rewarding model Daviesia. Moreover, the exaggerated UV reflectance of Diuris flowers impacted pollinators' visitation at an optimal distance from Da. decurrens, and the effect decreased when orchids were too close or too far away from the model. Our findings support the hypothesis that salient UV flower signaling plays a functional role in visual floral mimicry, likely exploiting perceptual gaps in bee neural coding, and mediates the plant pollinia removal at much greater spatial scales than previously expected. The ruse works most effectively at an optimal distance of several meters revealing the importance of salient visual stimuli when mimicry is imperfect. Donkey orchids mimic and exaggerate UV reflectance signals of rewarding model pea plants to attract pollinators. The ruse works exclusively from afar when the orchid is at an optimal distance away from the pea it mimics. Our findings explain the adaptive significance of salient UV display in long‐range plant‐bee communication and why deceptive plants succeed despite imperfect floral mimicry.
Journal Article
Honey Bee Foraging Decisions Are Shaped by Floral Trait Distinctiveness and Perception of Gains or Losses
The floral choices of honey bees (Apis mellifera) were studied using artificial flower patches to understand how foragers manage changing floral landscapes. Bees were observed under conditions where reward quality changed over time in blue and white flowers. We evaluated initial learning and reversal learning, varying the magnitude of reward quality-difference and color distinctness in the honey bee’s color vision space (being either similar or more distinct). Flower color fidelity was higher when flower colors were more distinct, but it also made it more difficult for bees to abandon the flower color in the reversal learning phase. Smaller differences in reward quality reduced flower color fidelity and promoted reversal learning. When reward difference between flower colors was created (initial learning), a decrease in one of the flower color rewards elicited a stronger behavioral response from foragers than an increase in reward. Our work highlights that bees used and integrated information from different axes of information: distinctiveness of color cues, magnitude of reward difference, and directionality (being stronger for losses than gains). Thus, flower distinctiveness, opportunity cost, and loss aversion drive honey bee foraging decisions. Higher accuracy at initial learning has stronger costs in behavioral adaptations at changing floral landscapes.
Journal Article
Nesting Biology and Ecology of a Resin Bee, Megachile cephalotes (Megachilidae: Hymenoptera)
We report the nesting biology and ecology of Megachile cephalotes Smith, 1853 for the first time in Pakistan. Wooden and bamboo trap nests were deployed at three different locations in Bahawalpur district, Pakistan, from January 2020 to May 2021. A total of 242 nests of M. cephalotes were occupied in all three locations with the maximum abundance in the Cholistan Institute of Desert Studies. Megachile cephalotes remained active from March to September (the spring and summer seasons). In a nest, females made 7–8 brood cells each having a length of 1.2–2.3 cm. Plant resin was used to construct cells and mud or animal dung to plug the nest entrance. A vestibular cell was also made between the outermost brood cell and the nest entrance that ranged from 1.4 to 2.5 cm in length. No intercalary cells were observed in the nests. The males took 65.3 days to become adults, while the females took 74.78 days. The sex ratio was significantly biased toward females in all three locations. Grewia asiatica was the predominant pollen grain species found in the brood cells. Megachile cephalotes were observed collecting resin from Acacia nilotica, Prosopis juliflora, and Moringa oleifera. Three cleptoparasites of this species were also recorded: Euaspis carbonaria, Coelioxys sp., and Anthrax sp. This study set up a background to encourage new studies on artificial nesting and provides tools for proper biodiversity management and conservation.
Journal Article
Pollen mixing in pollen generalist solitary bees: a possible strategy to complement or mitigate unfavourable pollen properties?
Generalist herbivorous insects, which feed on plant tissue that is nutritionally heterogeneous or varies in its content of secondary metabolites, often benefit from dietary mixing through more balanced nutrient intake or reduced exposure to harmful secondary metabolites. Pollen is similarly heterogeneous as other plant tissue in its content of primary and secondary metabolites, suggesting that providing their offspring with mixed pollen diets might be a promising strategy for pollen generalist bees to complement nutrient imbalances or to mitigate harmful secondary metabolites of unfavourable pollen. In the present study, we compared larval performance of the pollen generalist solitary bee species Osmia cornuta (Megachilidae) on five experimental pollen diets that consisted of different proportions of unfavourable pollen diet of Ranunculus acris (Ranunculaceae) and favourable pollen diet of Sinapis arvensis (Brassicaceae). In addition, we microscopically analysed the pollen contained in the scopal brushes of field‐collected females of O. cornuta and three closely related species to elucidate to what degree these pollen generalist bees mix pollen of different hosts in their brood cells. In striking contrast to a pure Ranunculus pollen diet, which had a lethal effect on most developing larvae of O. cornuta, larval survival, larval development time and adult body mass of both males and females remained nearly unaffected by the admixture of up to 50% of Ranunculus pollen diet to the larval food. Between 42% and 66% of all female scopal pollen loads analysed contained mixtures of pollen from two to six plant families, indicating that pollen mixing is a common behaviour in O. cornuta and the three related bee species. The present study provides the first evidence that the larvae of pollen generalist bees can benefit from the nutrient content of unfavourable pollen without being negatively affected by its unfavourable chemical properties if such pollen is mixed with favourable pollen. We conclude that the widespread pollen mixing by females of pollen generalist bees should also be considered as a possible strategy to exploit flowers with unfavourable pollen and to optimize larval food quality.
Journal Article
Non-bee insects are important contributors to global crop pollination
Wild and managed bees are well documented as effective pollinators of global crops of economic importance. However, the contributions by pollinators other than bees have been little explored despite their potential to contribute to crop production and stability in the face of environmental change. Non-bee pollinators include flies, beetles, moths, butterflies, wasps, ants, birds, and bats, among others. Here we focus on non-bee insects and synthesize 39 field studies from five continents that directly measured the crop pollination services provided by non-bees, honey bees, and other bees to compare the relative contributions of these taxa. Non-bees performed 25–50% of the total number of flower visits. Although non-bees were less effective pollinators than bees per flower visit, they made more visits; thus these two factors compensated for each other, resulting in pollination services rendered by non-bees that were similar to those provided by bees. In the subset of studies that measured fruit set, fruit set increased with non-bee insect visits independently of bee visitation rates, indicating that non-bee insects provide a unique benefit that is not provided by bees. We also show that non-bee insects are not as reliant as bees on the presence of remnant natural or seminatural habitat in the surrounding landscape. These results strongly suggest that non-bee insect pollinators play a significant role in global crop production and respond differently than bees to landscape structure, probably making their crop pollination services more robust to changes in land use. Non-bee insects provide a valuable service and provide potential insurance against bee population declines.
Journal Article
The potential and realized foraging movements of bees are differentially determined by body size and sociality
Reversing biodiversity declines requires a better understanding of organismal mobility, as movement processes dictate the scale at which species interact with the environment. Previous studies have demonstrated that species foraging ranges, and therefore, habitat use increases with body size. Yet, foraging ranges are also affected by other life-history traits, such as sociality, which influence the need of and ability to detect resources. We evaluated the effect of body size and sociality on potential and realized foraging ranges using a compiled dataset of 383 measurements for 81 bee species. Potential ranges were larger than realized ranges and increased more steeply with body size. Highly eusocial species had larger realized foraging ranges than primitively eusocial or solitary taxa. We contend that potential ranges describe species movement capabilities, whereas realized ranges depict how foraging movements result from interactions between species traits and environmental conditions. Furthermore, the complex communication strategies and large colony sizes in highly eusocial species may facilitate foraging over wider areas in response to resource depletion. Our findings should contribute to a greater understanding of landscape ecology and conservation, as traits that influence movement mediate species vulnerability to habitat loss and fragmentation.
Journal Article
Specialized Bees Fail to Develop on Non-host Pollen: Do Plants Chemically Protect Their Pollen?
Bees require large amounts of pollen for their own reproduction. While several morphological flower traits are known to have evolved to protect plants against excessive pollen harvesting by bees, little is known on how selection to minimize pollen loss acts on the chemical composition of pollen. In this study, we traced the larval development of four solitary bee species, each specialized on a different pollen source, when reared on non-host pollen by transferring unhatched eggs of one species onto the pollen provisions of another species. Pollen diets of Asteraceae and Ranunculus (Ranunculaceae) proved to be inadequate for all bee species tested except those specialized on these plants. Further, pollen of Sinapis (Brassicaceae) and Echium (Boraginaceae) failed to support larval development in one bee species specialized on Campanula (Campanulaceae). Our results strongly suggest that pollen of these four taxonomic groups possess protective properties that hamper digestion and thus challenge the general view of pollen as an easy-to-use protein source for flower visitors.
Journal Article
Hedgerow restoration promotes pollinator populations and exports native bees to adjacent fields
In intensive agricultural landscapes, restoration within farms could enhance biodiversity and ecosystem services such as pollination by native pollinators. Although governments and conservation groups are promoting small-scale restoration on working farms, there are few studies that assess whether these practices enhance pollinator communities in restored areas. Further, there is no information on whether floral enhancements will deplete pollinators in adjacent fields by concentrating ambient populations or whether they result in a net increase in abundance in adjacent farm fields. We investigated whether field edges restored with native perennial plants in California's Central Valley agricultural region increased floral abundance and potential bee nesting sites, and native bee and syrphid fly abundance and diversity, in comparison to relatively unmanaged edges. Native bees and syrphid flies collected from flowers were more abundant, species-rich, and diverse at hedgerow sites than in weedy, unmanaged edges. Abundance of bees collected passively in pan traps was negatively correlated with floral abundance, was significantly different from communities captured by net sampling from flowers, and did not distinguish between site types; we therefore focused on the results of net samples and visual observations. Uncommon species of native bees were sevenfold more abundant on hedgerow flowers than on flowers at weedy, unmanaged edges. Of the species on flowers at hedgerows, 40% were exclusive to hedgerow sites, but there were no species exclusively found on flowers at control sites. Hedgerows were especially important for supporting less-common species of native bees in our intensive agricultural landscape. Hedgerows did not concentrate ambient native bee, honey bee, or syphid fly populations, and they acted as net exporters of native bees into adjacent fields. Within-farm habitat restoration such as hedgerow creation may be essential for enhancing native pollinator abundance and diversity, and for pollination services to adjacent crops.
Journal Article