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Context Biotic resource exploitation is a critical determinant of species’ distributions. However, quantifying resource exploitation patterns through space and time can be difficult, complicating their incorporation in spatial ecology studies. Therefore, understanding the local drivers of spatial patterns of resource exploitation may contribute to better large-scale species distribution models. Objectives We investigated (1) how the resource exploitation patterns of two trophic interactions (plant–insect) are explained by insect behaviour, resource aggregation, and potential insect-insect interactions. We also analyzed how (2) resource patch size and (3) resource accessibility in a heterogeneous landscape affected host exploitation patterns. Methods We quantified nectar robbing by insects in the genus Bombus (bumblebees) and seed predation by Brachypterolus vestitus larvae (Antirrhinum beetle) on Antirrhinum majus L. (wild snapdragons) in the Pyrenees Mountains, Catalonia, Spain. We tested hypotheses about resource exploitation by integrating spatial analyses at multiple scales. Results Both trophic interactions were aggregated, explained by the aggregation of their resource. At some scales, nectar robbing is more aggregated than the resource. Trophic interaction abundance is proportional to resource patch size, following the ideal free distribution model. Landscape features do not explain the locations exploited. Nectar robbing and seed predation occur together more often than expected. Conclusions Our findings suggest that multiple biotic and ecological spatial factors may simultaneously affect resource exploitation at a local scale. These findings should be considered when developing agricultural projects, management plans and conservation policies.

Abstract The ontogeny of nectar robbing by pollinators is not well understood. In this study, we investigated the interplay of pre-existing biases and experience in the expression of nectar-robbing behavior by common eastern bumble bee (Bombus impatiens) workers. Flower-naïve bees were released individually into an arena containing six live Tecoma stans flowers in one of two treatments. One treatment consisted of open flowers bearing a single artificial slit, allowing the bee to rob or enter legitimately for nectar, while the other consisted of flowers bearing slits, whose corollas were plugged with cotton, requiring the bee to rob for nectar. A subset of bees was tested twice, once on each treatment; the order of treatments was balanced across bees. Results showed that first attempts by flower-naïve bees were biased nearly absolutely towards legitimate visitation regardless of flower treatment. Most bees in both treatment groups robbed over the course of a trial, but plugged flowers were robbed significantly more. Previous experience affected robbing frequency on subsequent visits, suggestive of learning; bees induced to rob on plugged flowers tended to continue to rob even when legitimate access was restored. We speculate that the initial bias towards legitimate visits is due to the flower corolla’s distinctive odor and nectar guides, to which bees respond innately. Bees nevertheless readily learn to rob, particularly when it is the only option for extracting nectar. Our findings support the view that studies of cognition are essential to understanding the pattern of cooperation and conflict in plant-pollinator mutualism.Significance statementNectar-robbing behavior is widely observed among pollinators in nature. Unlike visitation of flowers through the floral entrance, nectar robbing often does not transfer pollen. However, despite the importance of nectar robbing on plant fitness, little is known about the ontogeny of nectar-robbing behavior. In this study, we found that naïve Bombus impatiens workers strongly preferred legitimate visits over nectar robbing on their first visits to live flowers. However, bees quickly switched to nectar robbing when nectar could not be accessed legitimately and continued robbing even when legitimate access is restored. Our results suggest that flowers may take advantage of their pollinators’ innate responses for their own or mutual gain, but also that pollinators can overcome this manipulation through learning.

In a social species like the honey bee (Apis mellifera), changes in foraging strategy require shifts in several groups of specialized workers that are involved in collecting, storing, and processing food. In cases of extreme food shortage, honey bee colonies can switch to a high-risk, high-reward foraging tactic known as honey robbing, which involves stealing mature honey from other colonies. Colonies engaged in honey robbing show a corresponding increase in defensive behaviors displayed by specialist guard bees, presumably because the conditions that provoke robbing also increase the risk of colony invasion. Previous studies suggest aggressive behaviors displayed by robbing forager nestmates modulate guard defensiveness. In the current study, we evaluated which aspects of the robbing experience likely alter forager aggression, and in turn, guard defensiveness. We trained colonies to visit feeders containing either raw honey or a sucrose solution and examined whether food type, experience of conflict at the feeder, or other abiotic cues that reflect the time of the season best explain variation in guard defensiveness. We found little evidence that food type influences forager interactions with guards. Rather, conflict at the feeder is the best predictor of increased aggressive interactions, even when accounting for the effects of seasonal change. Thus, intraspecific conflict at the food resource during robbing may drive shifts in individual forager aggression, activating guard defensiveness as one component of a syndrome of colony-level changes required to accommodate the robbing foraging tactic.Significance statementHoney bees possess an extreme foraging tactic that they employ under conditions of resource scarcity. This tactic, honey robbing, requires coordinated changes among worker bees to accommodate enhanced food collection, processing, and storing, as well as nest defense. In a previous study, we showed that robbing foragers show unusually high aggression, and that this shift may trigger greater defensiveness from nestmate guards once foragers return home. Here, we explored the cues that coordinate the change in defensive effort from guards and find that forager conflict at the food resource is a strong predictor of guard defensiveness. These results suggest that guards use behavioral cues from their own foragers to estimate their risk of attack and increase their defensiveness accordingly.

Cities are complex socioecological systems, yet most urban ecology research does not include the influence of social processes on ecological outcomes. Much of the research that does address social processes focuses primarily on their effects on biotic community composition, with less attention paid to how social processes affect species interactions. Linking social processes to ecological outcomes is complicated by high spatial heterogeneity in cities and the potential for scale mismatch between social and ecological processes, and the indicators used to assess those processes. Here, we assessed how social and ecological processes jointly influence the frequency and outcomes of species interactions among the native perennial vine Gelsemium sempervirens and its insect pollinators, nectar robbers, and florivores across 28 residential subdivisions in the Research Triangle region, NC, USA. We integrated data on socioeconomic attributes (mean property value, mean property size, subdivision age), vegetation attributes (forest cover and richness and density of managed and unmanaged floral resources), species interactions (conspecific and heterospecific pollen deposition, nectar robbing, florivory), and Gelsemium reproduction (fruit set, seeds per fruit) using structural equation modeling to understand the causal links between socioeconomic attributes, vegetation attributes, and interaction frequency and outcome. Among socioeconomic attributes, property value was the strongest predictor of interaction frequency, having both direct and vegetation-mediated indirect effects on pollination and florivory. However, the effect of socioeconomic attributes on plant reproduction was small. Overall, we were able to explain only a small amount of the variation in any species interaction or reproduction measure. This may be due to the functional similarity of subdivisions, despite large variation in both socioeconomic and vegetation attributes, or may reflect scale mismatch between the ecological and socioeconomic variables. Our findings highlight the need to develop scale-appropriate indicators to improve our understanding of the links between social and ecological processes in urban landscapes.

Honey robbing, as an extreme adaptive response of honey bee colonies to resource scarcity, poses devastating threats to apiaries, yet the underlying molecular mechanisms remain poorly understood. We compared morphological traits and survival rates between robber bees and normal foragers and conducted proteomic sequencing of bee head samples. The results demonstrated that robber bees exhibited darker tergite coloration and significantly shortened lifespan. Proteomic analysis revealed that the darker coloration was primarily attributed to enhanced cuticular melanin deposition mediated by upregulated laccase-5, while the shortened lifespan mainly resulted from oxidative stress and immune suppression: the downregulation of heat shock protein 75 kDa and glutathione transferase weakened antioxidant capacity, and despite compensatory upregulation of the cytochrome P450 enzyme system, flavin-containing monooxygenases and other enzymes, oxidative damage continued to accumulate. Concurrently, downregulation of Defense protein 3 and C-type lectin 5 caused immune deficiency in robber bees. The results also showed metabolic and protein synthesis reprogramming in robber bees, specifically manifested by upregulated key enzymes in nicotinate and nicotinamide metabolism, the pentose phosphate pathway, and nucleotide metabolism, along with activation of protein synthesis-transport-export systems. We found that robber bees employ a “metabolic-synthetic co-enhancement” physiological strategy to boost short-term foraging efficiency, but this strategy simultaneously induces oxidative damage and immune suppression, ultimately shortening their lifespan. This study provides the first proteomic evidence revealing the physiological trade-offs underlying this behavior at the molecular level, offering novel insights into the physiological costs of behavioral adaptation in animals.

Honey robbing, which typically occurs during times of food scarcity, is a perilous foraging strategy for bee colonies and presents a formidable challenge in the realm of beekeeping. This article provides a comprehensive and multifaceted exploration of honey robbing, including the morphology, behavioral traits, timing, and scope of this phenomenon. This exploration elucidates the specific manifestations of honey robbing, offering readers a deeper understanding of its various facets. Next, this article investigates the root causes of honey robbing by examining both abiotic and biotic factors. The resulting harms are outlined, and corresponding preventive and control measures are suggested. Finally, the article succinctly summarizes the current obstacles in research related to honey robbing and outlines promising avenues for future exploration. The objective of this study was to elucidate the occurrence mechanism of honey robbing, ultimately aiming to contribute to the sustainable growth of the beekeeping industry.

How do nectar-feeding animals choose among alternative flower-handling tactics? Such decisions have consequences not only for animal fitness (via food intake) but for plant fitness as well: many animals can choose to \"rob\" nectar through holes chewed in the base of a flower instead of \"legitimately\" collecting it through the flower's opening, thus failing to contact pollen. Although variation within a species in these nectar-foraging tactics is well documented, it is largely unknown why some individuals specialize (at least in the short term) on robbing, others on legitimate visitation, and others switch between these behaviors. We investigated whether the tendency to rob nectar through previously-made holes (secondary robbing) is influenced by prior foraging experience. In a laboratory experiment, we trained groups of bumble bees (Bombus impatiens) either to visit artificial flowers legitimately or to secondary-rob; a third group received no training. On subsequent visits to flowers, all bees had the opportunity to use either foraging tactic. We found that experience did affect bees' tendency to secondary-rob: trained bees were more likely to adopt the tactic they had previously experienced. Untrained bees initially sampled both tactics, but over time preferred to secondary-rob. Experience also increased bees' success at gaining nectar from flowers, but only when visiting flowers legitimately (the less preferred tactic). Overall, these findings highlight the importance of experience in animals' choices of alternative handling tactics while foraging and help explain long-standing observations of variation in nectar-robbing behavior among individuals of the same population.

Nectar robbing can affect plant reproductive success directly by influencing female and male fitness, and indirectly by affecting pollinator behavior. Flowers have morphological and chemical features that may protect them from nectar robbers. Previous studies on nectar robbing have focused mainly on homotypic plants. It remains unclear how nectar robbing affects the reproductive success of distylous plants, and whether defense strategies of two morphs are different. Nectar‐robbing rates on the long‐ and short‐styled morph (L‐morph, S‐morph) of the distylous Tirpitzia sinensis were investigated. We compared floral traits, the temporal pattern of change in nectar volume and sugar concentration, nectar secondary metabolites, and sugar composition between robbed and unrobbed flowers of two morphs. We tested direct effects of nectar robbing on female and male components of plant fitness and indirect effects of nectar robbing via pollinators. Nectar‐robbing rates did not differ between the two morphs. Flowers with smaller sepals and petals were more easily robbed. The floral tube diameter and thickness were greater in L‐morphs than in S‐morphs, and the nectar rob holes were significantly smaller in L‐morphs than in S‐morphs. Nectar robbing significantly decreased nectar replenishment rate but did not affect nectar sugar concentration or sugar composition. After robbery, the quantities and diversity of secondary compounds in the nectar of S‐morphs increased significantly and total relative contents of secondary compounds in L‐morphs showed no obvious changes. Nectar robbing could decrease female fitness by decreasing pollen germination rate and thus decreasing seed set. Nectar robbing had no significant effects on male fitness. Robbed flowers were less likely to be visited by hawkmoth pollinators, especially in S‐morphs. These results suggest that nectar robbing could directly and indirectly decrease the female fitness of T. sinensis, and different morphs have evolved different defense mechanisms in response to nectar‐robbing pressure. Nectar robbing could directly and indirectly decrease the female fitness of Tirpitzia sinensis, and different morphs have evolved different defense mechanisms in response to nectar robbing pressure.

Consumption of pollination reward by felonious means in a plant species can influence the foraging behavior of its pollinator and eventually the reproductive success. So far, studies on this aspect are largely confined to interaction involving plant-pollinators and nectar robbers or thieves. However, a foraging guild in such interactions may also include floral herbivores or florivores. There is a paucity of information on the extent to which nectar larcenists may influence the foraging behavior of the pollinator and reproductive fitness of plants in the presence of a florivore. We investigated various forms of larceny in the natural populations of Aerides odorata , a pollinator-dependent and nectar-rewarding orchid. These populations differed in types of foraging guild, the extent of larceny (thieving/robbing), which can occur with or without florivory, and natural fruit-set pattern. The nectariferous spur of the flower serves as an organ of interest among the foraging insects. While florivory marked by excision of nectary dissuades the pollinator, nectar thieving and robbing significantly enhance visits of the pollinator and fruit-set. Experimental pollinations showed that the species is a preferential outbreeder and experiences inbreeding depression from selfing. Reproductive fitness of the orchid species varies significantly with the extent of floral larceny. Although nectar thieving or robbing is beneficial in this self-compatible species, the negative effects of florivory were stronger. Our findings suggest that net reproductive fitness in the affected plant species is determined by the overarching effect of its breeding system on the overall interacting framework of the foraging guild.

Abstract Many plants pollinated by nectar-foraging animals have to maintain a balance between legitimate visitor attraction strategies and mechanisms that minimize illegitimate visits. This study investigated how floral display and neighboring species composition influences nectar robbing by hummingbirds in the tropical ornithophilous herb Heliconia spathocircinata. We tested the role of inflorescence display, flower abundance, and neighboring species in the reduction of nectar robbing in H. spathocircinata. Our results indicate that nectar robbing hummingbird activity was higher in moderately large inflorescence displays and that the frequency of nectar robbing in H. spathocircinata decreases with increased flower abundance and the presence of neighboring plant species. Neighboring non-ornithophilous plants decreased the frequency of nectar robbing in H. spathocircinata flowers to a greater extent than ornithophilous ones. These results suggest that nectar robbing hummingbirds are attracted to similar conditions that attract legitimate visitors and that spatial aggregation and mixed-species displays may represent a mechanism to dilute nectar robbing effects at an individual level.