Intertegular Distance Research Articles

Age dominates flight distance and duration, while body size shapes flight speed in Bombus terrestris L. (Hymenoptera: Apidae).

Flight plays a crucial role in the fitness of insect pollinators, such as bumblebees. Despite their relatively large body size compared with their wings, bumblebees can fly under difficult ambient conditions, such as cooler temperatures. While their body size is often positively linked to their foraging range and flight ability, the influence of age remains less explored. Here, we studied the flight performance (distance, duration and speed) of ageing bumblebee workers using tethered flight mills. Additionally, we measured their intertegular distance and dry mass as proxies for their body size. We found that the flight distance and duration were predominantly influenced by age, challenging assumptions that age does not play a key role in foraging and task allocation. From the age of 7 to 14 days, flight distance and duration increased sixfold and fivefold, respectively. Conversely, the body size primarily impacted the maximum and average flight speed of workers. Our findings indicate that age substantially influences the flight distance and duration in bumblebee workers, affecting foraging performance and potentially altering task allocation strategies. This underscores the importance of considering individual age and physiological changes alongside body size/mass in experiments involving bumblebee workers.

Land-use change alters specialist bee diet and drives body size declines

ContextLand-use change can cause decreases in plant abundance and richness and the replacement of wild plants with domesticated plants. Changes in plant community composition disrupt mutualistic plant-pollinator interactions with ecological consequences for plants and pollinators, and especially for specialists that rely on certain plants.ObjectivesWe assessed the effects of land-use change and subsequent shifts in plant communities on resource collection and body size for a bee pollinator, Habropoda laboriosa, a purported specialist of blueberries and related Ericaceae plants.MethodsWe collected Habropoda laboriosa across a gradient of land use in north-central Florida including agricultural, natural, and urban habitats. We assessed landcover and floral community composition at each site and related these to bee body size (intertegular distance) and resource use (proportion host plant pollen and pollen diversity collected).ResultsHost plant pollen collection and bee body size generally responded similarly to the landscape, both increasing with habitats containing host plants (blueberry farms and natural habitat) but decreasing with urban development. However, host pollen collection and bee body size responded in opposite ways to overall cropland in the landscape, with cropland negatively affecting body size despite positively affecting host pollen collection, indicating other factors associated with cropland might drive declines in bee body size.ConclusionsLand-use change can adversely affect bee diet and body size, and changes in diet likely contribute to changes in body size over time. Specialists are particularly at risk for negative impacts of land-use change due to their inability to shift plant hosts.

Landscape composition affects parasitoid body size in species-specific manner: A case study in Asian rice systems

The top-down effect of natural enemies on pests is a crucial ecosystem service supporting integrated pest management. However, the variation in morphological traits of parasitoids in different landscape contexts and the differences in parasitoid emergence rate caused by this variation are still poorly known. We measured the inter-tegular distance (ITD) and body mass of three parasitoids– Cotesia chilonis (Munakata), Eriborus sinicus (Holmgren), and Microgaster russata Haliday – on overwintering larvae of Chilo suppressalis (Walker), the rice stem borer (RSB), collected from 20 rice paddies along a landscape heterogeneity gradient. Our objectives were to assess how landscape composition and landscape diversity affect functional traits (ITD and body mass) of species-specific parasitoid, and individual body size for its impact on biological control. From a total of 5002 sampled individuals of the three parasitoids, regression analysis revealed that (1) the presence of water bodies within the landscape respectively positive affected the ITD of E. sinicus and M. russata at 2000 m scales, landscape factors had yet no discernible effects on either the body size (ITD or body mass) of C. chilonis, (2) habitats with high landscape diversity had a negative effect on body size (ITD and body mass) of the solitary parasitoids E. sinicus at 200 m scales, and (3) a significantly negative correlation was found between the parasitoid emergence rate and ITD of E. sinicus. Our findings suggest that parasitoids’ body sizes may respond differently among species to landscape features. Solitary parasitoids in our study were more sensitive to variation in habitat resource-availability than was the gregarious parasitoid. We conclude that landscape habitat changes can affect the body size and parasitism of parasitoids, modifying their biocontrol services against pests.

Neotropical stingless bees display a strong response in cold tolerance with changes in elevation.

Tropical pollinators are expected to experience substantial effects due to climate change, but aspects of their thermal biology remain largely unknown. We investigated the thermal tolerance of stingless honey-making bees, the most ecologically, economically and culturally important group of tropical pollinators. We assessed changes in the lower (CTMin) and upper (CTMax) critical thermal limits of 17 species (12 genera) at two elevations (200 and 1500m) in the Colombian Andes. In addition, we examined the influence of body size (intertegular distance, ITD), hairiness (thoracic hair length) and coloration (lightness value) on bees' thermal tolerance. Because stingless beekeepers often relocate their colonies across the altitudinal gradient, as an initial attempt to explore potential social responses to climatic variability, we also tracked for several weeks brood temperature and humidity in nests of three species at both elevations. We found that CTMin decreased with elevation while CTMax was similar between elevations. CTMin and CTMax increased (low cold tolerance and high heat tolerance) with increasing ITD, hair length and lightness value, but these relationships were weak and explained at most 10% of the variance. Neither CTMin nor CTMax displayed significant phylogenetic signal. Brood nest temperature tracked ambient diel variations more closely in the low-elevation site, but it was constant and higher at the high-elevation site. In contrast, brood nest humidity was uniform throughout the day regardless of elevation. The stronger response in CTMin, and a similar CTMax between elevations, follows a pattern of variation documented across a wide range of taxa that is commonly known as the Brett's heat-invariant hypothesis. Our results indicate differential thermal sensitivities and potential thermal adaptations to local climate, which support ongoing conservation policies to restrict the long-distance relocations of colonies. They also shed light on how malleable nest thermoregulation can be across elevations.

Body Size Variation in a Social Sweat Bee, Halictus ligatus (Halictidae, Apoidea), across Urban Environments.

Simple SummaryMany animal species that dwell in cities have altered aspects of their behavior, morphology, and physiology in order to survive in human-dominated environments. One way in which animals can adapt to survive in novel habitats is by shifting their body size. Body size is an important and flexible trait for insects because the ability to vary body size is linked to better survival and reproduction. In this study, we quantified body size variation in a species of sweat bee and compared the variation between bees residing in three different urban cities. Though studies have assessed urban bee body size previously, this is the first to compare bees from different cities. Similar to the human experience, no two cities are alike for bees. Therefore, we predicted that bees would show differences in the spread of body size in order to adapt to each unique city. We found that bees in three different environments all showed high variation in body size, but that the variation differed depending on location. This study is one of the first multi-city studies, and this is a trend we hope continues as urban research advances.High morphological variation is often associated with species longevity, and it is hypothesized that urban-dwelling species may require more plasticity in functional traits such as body size in order to maximize fitness in heterogeneous environments. There has been published research regarding the functional trait diversity of urban bee pollinators. However, no two cities are identical, so the implementation of multi-city studies is vital. Therefore, we compared body size variation in female Halicus ligatus sweat bees from May–October 2016 from three distinct Midwestern United States cities: Chicago, Detroit, and Saint Louis. Additionally, to elucidate potentially influential environmental factors, we assessed the relationship between temperature and measured body size. We collected bees in community gardens and urban farms and measured their head width and intertegular distance as a proxy for overall body size. We utilized an ANCOVA to determine whether body size variation differed significantly across the three surveyed cities. Results indicated that H. ligatus females in Chicago, Detroit, and Saint Louis had significantly different body size ranges. These findings highlight the importance of intraspecific body size variation and support our prediction that bees from different urban environments will have distinct ranges in body size due to local ecological factors affecting their populations. Additionally, we found a significant influence of temperature, though this is probably not the only important ecological characteristic impacting bee body size. Therefore, we also provided a list of predictions for the future study of specific variables that are likely to impact functional trait diversity in urban bees.

Adult body size measurement redundancies in Osmia lignaria and Megachile rotundata (Hymenoptera: Megachilidae).

Metrics to assess relative adult bee body size have included both mass and morphometrics, but these metrics may not equally or reliably estimate body size for all bee species and in all situations, due to bee age, diet, and/or environment. Understanding the relationships between different metrics and possible redundancies in the information they afford is important but not always known. Body size measurements provide valuable data for interpreting research outcomes for managed solitary bees, including Osmia lignaria Say and Megachile rotundata F. (Hymenoptera: Megachilidae). Applied studies of these important and readily available U.S. crop pollinators focus on refining commercial management practices, and basic empirical studies in various scientific disciplines (from genomics to ecology) employ them as model systems to study solitary bees. To examine common metrics of body size, we measured head capsule width (HCW), intertegular distance (ITD), and fresh and dry weights of newly emerged adults of both species. Using linear and exponential models, we determined relationships between these body size metrics. For M. rotundata, linear models best described relationships between ITD and all other metrics, and between HCW and fresh and dry weights. For O. lignaria, linear models best fit relationships between all metrics except for fresh weight with both ITD and HCW, which were fitted better with exponential models. For both species, model fits were strongest when males and females were pooled. Depending on the study question, knowing that only one metric may reliably measure body size can simplify evaluations of O. lignaria and M. rotundata responses to artificial or environmental variables.

Specialist Bee Species Are Larger and Less Phylogenetically Distinct Than Generalists in Tropical Plant–Bee Interaction Networks

Bee pollinators are key components of terrestrial ecosystems. Evidence is mounting that bees are globally in decline, and species with a higher degree of specialization are the most vulnerable to local extinction. However, ecological features that could explain bee specialization remain poorly tested, especially in tropical species. Here, we aim to determine the most specialized bee species and their associated ecological traits in tropical plant–bee interaction networks, answering three questions: (1) Which bees in the interaction networks are specialists? (2) Is body size related to their role as specialists in interaction networks? (3) Are there phylogenetic relationships between the bee species identified as specialists? We used fifteen quantitative plant–bee interaction networks from different Brazilian biomes covering 1,702 interactions (386 bee and 717 plant species). We used the normalized degree (standardized number of partners) as a metric to determine trophic specialization of bee species. Body size was estimated by measuring intertegular distance (ITD), i.e., the distance between the bases of the wings on the thorax. Evolutionary distinctiveness (ED) was used to quantify species uniqueness, i.e., the singularity of species in the phylogenetic tree. Relationships between dietary specialism, ITD and ED were assessed using generalized linear models. We detected 34 specialist bee species (9% of total species), distributed in 13 genera, and four families. ITD and ED were important variables explaining the specialization of tropical bee species. Specialists were larger and less phylogenetically distinct than expected by chance. Based on a large data set covering some of the main tropical biomes, our results suggest that loss of specialist bees from Brazilian plant–bee networks could have deleterious consequences for native plant species preferentially pollinated by large-bodied bees. Moreover, by affecting more evolutionarily distinct species, i.e., those with fewer extant relatives, the loss of specialist bees will likely affect few clades but can result on considerable loss of evolutionary history and phylogenetic diversity in the Brazilian bee communities. The results are important for decision-making concerning conservation measures for these species and may also encourage the development of sustainable management techniques for bees.

Role of floral strips and semi-natural habitats as enhancers of wild bee functional diversity in intensive agricultural landscapes

Installing patches of flowering plants is a commonly used strategy to enhance refuge and food resources for pollinators in intensive agricultural landscapes. Here, we evaluated how floral strips and semi-natural habitats impact the taxonomic and functional diversity of wild bees in intensively farmed sunflower fields. Pan traps were used to assess bee richness and functional diversity at 22 sampling sites (11 sites were positioned in sunflower fields with floral strips, and 11 control sites were adjacent to semi-natural habitats). Five sampling levels were established in each field, positioned at different distances from the flower strip or semi-natural habitat. Wild bee species richness and functional richness were significantly higher inside floral strips and semi-natural habitats compared to sunflower fields. Functional redundancy was significantly higher inside agricultural fields compared to inside floral strips and semi-natural habitats. Sunflower fields with floral strips had lower Rao values compared to sunflower fields adjacent to semi-natural habitats. The community-weighted mean (CWM) of intertegular distance (distance between where wings attach to body) of wild bees was significantly higher in sunflower fields adjacent to semi-natural habitats. In comparison, the CWM of wing length varied across sampling levels in sunflower fields with semi-natural habitats. Our results show it is essential to have semi-natural habitats within intensive agricultural landscapes to ensure the conservation of wild bee diversity, while the installation of floral strips offers a partial substitute to enhance wild bee diversity when semi-natural habitats are scarce or absent.

Larvae of stingless bee Scaptotrigona bipunctata exposed to organophosphorus pesticide develop into lighter, smaller and deformed adult workers.

Organophosphorus pesticides such as chlorpyrifos are often used in agriculture due to their broad spectrum of action. However, this insecticide and acaricide is considered highly toxic to the environment and can cause toxicity in nontarget insects such as bees. In addition to adult individuals, immature can also be exposed to residues of this insecticide by larval food. Thus, we investigated the effects of chlorpyrifos concentrations on the larval development of stingless bee Scaptotrigona bipunctata workers reared invitro. We evaluated four different biomarkers: a) survival, b) development time, c) body mass and d) morphological characteristics (head width, intertegular distance, wing area and proportion of deformed bees). The exposure of the larvae to different doses of chlorpyrifos significantly reduced survival probability but did not cause changes in the development time. Regarding morphometric analysis, bees exposed to chlorpyrifos showed a reduction in body mass and size, and 28% of the emerged adults showed a reduction in wing area and deformations. Therefore, this work shows that S.bipunctata larvae exposed to the sublethal effects of chlorpyrifos are likely to have reduced chances of survival. However, if they emerge, they will be lighter, smaller and less able than equivalent but not exposed workers. These impaired attributes have the potential to compromise the future workforce in colonies exposed to this pesticide.

Functional groups of wild bees respond differently to faba bean Vicia faba L. cultivation at landscape scale

Abstract Concerns about insect declines are growing and the provisioning of ecosystem services like pollination may be threatened. To safeguard biodiversity, greening measures were introduced within the reform of the EU's Common Agricultural Policy. One measure commonly applied by farmers is the cultivation of nitrogen fixing crops. Although underlying studies are largely missing, this measure is criticized as providing no significant biodiversity benefit. Using a landscape‐scale approach, we selected 30 paired study landscapes (1 km × 1 km) in Germany, that is, 15 study landscapes with faba bean (FB) fields (Vicia faba L.) and 15 without any grain legumes. Flower‐visiting wild bees were recorded with transect walks at the field margins of different crops using a stratified sampling approach. We analysed the effect of FB cultivation and landscape composition on the abundance and species richness of wild bees as well as on the functional composition of the bee communities. Bumblebee densities (Bombus spp. Latreille) were more than twice as high in FB compared to control landscapes after the flowering of the beans. Non‐Bombus wild bee densities, however, were not affected by FB cultivation, but were enhanced by increasing amounts of semi‐natural habitats (SNH). After the beans' blooming had ceased, FB landscapes had a higher proportion of wild bees collecting pollen from Fabaceae than control landscapes. The community‐weighted means for bee size, measured as intertegular distance, were not affected by FB cultivation, but we found smaller species and species with shorter tongues with an increasing percentage of SNH. Synthesis and applications. The cultivation of faba bean Vicia faba L. strongly increased bumblebee densities throughout the season. This indicates that also on‐field greening measures can support biodiversity. Nevertheless, since only functional groups adapted to faba bean benefit, measures to promote semi‐natural habitats in agricultural landscapes need to be implemented. We conclude that the combination of on‐ and off‐field measures is essential to maintain farmland biodiversity and the Common Agricultural Policy should furthermore promote both.

Male strategies and mating behavior in the Neotropical bee Epicharis (Anepicharis) dejeanii (Apidae: Centridini)

This study describes the mating behavior of Epicharis dejeanii and evaluates the reproductive strategies employed by males during the reproductive period. Samples were collected in an aggregation of E. dejeanii nests, located in southern Brazil. Observations on mating behavior and male patrols were performed for 37 days, from 06:00 to 18:00, during two reproductive periods, in the wet-warm season. During the samplings, males patrolling and/or copulating with E. dejeanii females were collected and used for morphometric measurements. Males were active in November and December when they showed two mating patrol strategies: i) flyover near the ground; (ii) flights over trees (at heights of approximately 2.5 m and distant about 2 to 5 m from nesting aggregation). The results revealed a greater head width and intertegular distance among males patrolling above the plants, suggesting that the adopted patrol strategy has an association with the body size of males. However, both strategies were effective in copulation success. The males demonstrated a peak of activity in the patrol for females between 9:00 and 11:30 hours, which coincided with the period of greatest emergence of females, as well as when the largest number of matings were observed.

Exploring the importance of floral resources and functional trait compatibility for maintaining bee fauna in tropical agricultural landscapes

Loss of semi-natural habitats has been identified as a major driver for pollinator loss in agricultural landscapes. The challenge has been addressed in developed countries by creating flower strips and pollinator habitats in agricultural areas, but this approach has largely been overlooked in developing countries. However, even in countries that adopted pollinator-friendly measures, the complementarities between functional traits of plants and bees are not generally used as selection criteria for candidate species in floral strips. Furthermore, the combined effect of habitat variables that are likely to maximize bee visitation are also overlooked. In tropical developing countries, even the basic information to inform decision making is missing. This paper attempts to bridge this critical gap and reports how assemblages of different non-crop plants could be used to attract bees in tropical small landholdings by investigating non-crop plant identity, non-crop floral traits, bee traits and influential habitat variables at patch scale. Results showed that a combination of both non-crop flower density and diversity increased bee visitation at patch scale. Moreover, trait-based analyses revealed that bees with a larger inter-tegular distance, longer tongue frequently visited flowers with a longer corolla. This study demonstrates that both characteristics of non-crop flower patches and floral traits are important for effective management of non-crops in tropical farmland to attract pollinators with complementary functional traits. We have explored a range of non-crop plants that could be effectively sown to attract bees but recognise that more research is necessary in order to standardise their propagation, establishment and management techniques.

Patterns of pollen flow in monomorphic enantiostylous species: the importance of floral morphology and pollinators’ size

Enantiostyly is a floral polymorphism consisting in the presence of two floral morphs that differ in the deflection of the style to the right or left in the populations. Monomorphic enantiostyly consists in plants showing both morphs within an individual and is thought to promote pollen transference between morphs, reduce levels of self-pollination and geitonogamy and avoid damage to floral parts during pollinator’s visit. In this study, we examined the function of this floral polymorphism in a group of plants with non-typical enantiostylous characteristics, the family Vochysiaceae. In particular, we evaluated how floral morphology (both sexual organ separation and the match between complementary sexual organs in the morphs) is related to pollen deposition on the pollinators’ body and to patterns of pollen flow among individuals. For this, we used floral morphometrics, insect captures and fluorescent powder dyes. We confirmed that monomorphic enantiostyly increased pollen transference between morphs compared to non-enantiostyly. Moreover, pollen flow occurred only between flowers of opposite morph. We also observed that pollen deposition on the insect’s body depended on their body shape rather than floral morphology. In fact, an intertegular distance slightly larger than the anther–stigma distance in the flowers increased pollen transference because anthers filaments and stigmas are flexible, which facilitated pollen brushing on insects’ body when approaching the flowers. Since the species are self-incompatible, we further discuss the role of mirror flowers in the reduction of geitonogamy and inbreeding depression.

Wildfires Influence Abundance, Diversity, and Intraspecific and Interspecific Trait Variation of Native Bees and Flowering Plants Across Burned and Unburned Landscapes

Wildfire regimes are changing in the western United States, yet we have little basic understanding of how wildfires influence native bees, the resources they depend on for food and nesting, or the traits that influence their interactions with plants. In burned and unburned areas in Montana, USA, we investigated the abundance and diversity of native bees, floral and nesting resources, nesting success, and traits of flowers and bees. In two of the three localities studied, burned areas, including areas that burned with high-severity wildfires, supported higher density and diversity of native bees and the flowers they depend on for food and larval provisioning. Burned areas also had more bare ground for ground-nesting bees and more available coarse woody debris for cavity-nesting bees than unburned areas. Moreover, cavity-nesting bees were completely unsuccessful at nesting in artificial nesting boxes in unburned areas, while nesting success was 40% in burned areas. Mean bee intertegular distance (a trait strongly correlated with tongue length, foraging distance, and body size) was similar between burned and unburned areas. However, wildfires influenced both interspecific and intraspecific trait variation of bees and plants. Intraspecific variation in bee intertegular distance was higher in unburned than burned areas. Both interspecific and intraspecific variation in floral traits important for interactions with pollinators were generally higher in burned than unburned areas. Thus, wildfires generally increased the density and species diversity of bees and flowers as well as trait variation at both trophic levels. We conclude that wildfires – even large, high-severity wildfires – create conditions that support native bees and the resources they need to flourish, but that unburned areas maintain trait variation in landscape mosaics with heterogeneous fire conditions.

The allometry of proboscis length in Melittidae (Hymenoptera: Apoidae) and an estimate of their foraging distance using museum collections.

An appreciation of body size allometry is central for understanding insect pollination ecology. A recent model utilises allometric coefficients for five of the seven extant bee families (Apoidea: Anthophila) to include crucial but difficult-to-measure traits, such as proboscis length, in ecological and evolutionary studies. Melittidae were not included although they are important pollinators in South Africa where they comprise an especially rich and morphologically diverse fauna. We measured intertegular distance (correlated with body size) and proboscis length of 179 specimens of 11 species from three genera of Melittidae. With the inclusion of Melittidae, we tested the between family differences in the allometric scaling coefficients. AIC model selection was used to establish which factors provide the best estimate of proboscis length. We explored a hypothesis that has been proposed in the literature, but which has not been tested, whereby body and range sizes of bees are correlated with rainfall regions. We tested this by using body size measurements of 2109 museum specimens from 56 species of Melittidae and applied the model coefficients to estimate proboscis length and foraging distance. Our results from testing differences across bee families show that with the addition of Melittidae, we retained the overall pattern of significant differences in the scaling coefficient among Apoidea, with our model explaining 98% of the variance in species-level means for proboscis length. When testing the relationship between body size and rainfall region we found no relationship for South African Melittidae. Overall, this study has added allometric scaling coefficients for an important bee family and shown the applicability of using these coefficients when linked with museum specimens to test ecological hypothesis.

In vitro larval rearing protocol for the stingless bee species Melipona scutellaris for toxicological studies.

Brazil has the highest biodiversity of native stingless bees in the world. However, Brazilian regulations are based on protocols standardized by the Organization for Economic Cooperation and Development (OECD), which uses Apis mellifera as a model organism. The safety of the use of an exotic species as a substitute for a native species is a problem that concerns members of the academy and the government agencies responsible for studies of this nature in the neotropical regions where there are occurrences of stingless bee species. Regarding the exposure of larvae to pesticides, several indicators suggest that the same rearing method for A. mellifera cannot be applied to stingless bees, mainly because of their different feeding systems. Thus, it is necessary to establish an in vitro rearing method for native social bees. We developed a larval rearing method for the stingless bee species Melipona scutellaris and evaluated parameters such as the defecation rate, pupation, emergence, mortality and morphometry of the newly emerged workers. The control was represented by the morphometry of individuals that emerged from natural combs (in vivo). In addition, we determined the average lethal concentration (LC50) of the insecticide dimethoate, the standard active ingredient used for the validation of toxicity tests. Procedures conducted prior to the in vitro bioassays allowed us to obtain the actual dimensions of the rearing cells for making acrylic plates for use in establishing how much each larva consumes during its development, that is, determining how much larval food should be placed in every artificial cell. Tests performed with M. scutellaris indicated an average of 80.2% emergence of individuals relative to the larvae, 92.61% relative to the pupae and a mean of 7.42% larval mortality. The mean of the intertegular distance, head width and wing asymmetry parameters were not significantly different between individuals from the in vitro and in vivo rearing methods. The LC50 value determined was 27.48 ng dimethoate / μL diet. The method described for M. scutellaris showed development rates above OECD standards, which requires at least 75% emergence, and produced newly emerged workers with similar dimensions to those produced under natural conditions; thus these results enable their use as a rearing protocol for this species (or genus) and, consequently, their use in toxicity tests. The results produced with M. scutellaris are the first steps for a proposed toxicity test protocol for stingless bee larvae that can be standardized and included as a protocol in the OECD.

Body Size Influences Stingless Bee (Hymenoptera: Apidae) Communities Across a Range of Deforestation Levels in Rondônia, Brazil.

Developments in understanding bee responses to habitat loss indicate that body size is a trait with important consequences for conservation. Stingless bees (Hymenoptera, Apidae, Meliponini) are a diverse group of eusocial bees providing pollination services in tropical landscapes, exhibiting a large range in body size across species. We tested the effects of deforestation on the body sizes of stingless bee communities by using museum specimens and revisiting a previous effort that sampled stingless bee communities across varying levels of deforestation at 183 sites in Rondônia, Brazil, in 1996–1997. Body size measurements (intertegular distance) from 72 species collected were included as dependent variables in response to forest area, forest edge, and connectivity of forest patches at several spatial scales. We find that stingless bee body size is negatively related to forest cover: mean community body size was larger in areas with greater amounts of deforestation, and smaller in areas with less deforestation. Second, stingless bee species richness was positively associated with forest edge regardless of body size. Lastly, we find that as forest patch isolation increased, the stingless bee community body size also increased. These findings support hypotheses that small stingless bee species might be more negatively affected by deforestation, adding to the growing body of evidence that stingless bees require areas of intact forest in near proximity to other forest patches to conserve these diverse pollinator communities.

Pollinator size and its consequences: Robust estimates of body size in pollinating insects.

Body size is an integral functional trait that underlies pollination‐related ecological processes, yet it is often impractical to measure directly. Allometric scaling laws have been used to overcome this problem. However, most existing models rely upon small sample sizes, geographically restricted sampling and have limited applicability for non‐bee taxa. Allometric models that consider biogeography, phylogenetic relatedness, and intraspecific variation are urgently required to ensure greater accuracy. We measured body size as dry weight and intertegular distance (ITD) of 391 bee species (4,035 specimens) and 103 hoverfly species (399 specimens) across four biogeographic regions: Australia, Europe, North America, and South America. We updated existing models within a Bayesian mixed‐model framework to test the power of ITD to predict interspecific variation in pollinator dry weight in interaction with different co‐variates: phylogeny or taxonomy, sexual dimorphism, and biogeographic region. In addition, we used ordinary least squares regression to assess intraspecific dry weight ~ ITD relationships for ten bees and five hoverfly species. Including co‐variates led to more robust interspecific body size predictions for both bees and hoverflies relative to models with the ITD alone. In contrast, at the intraspecific level, our results demonstrate that the ITD is an inconsistent predictor of body size for bees and hoverflies. The use of allometric scaling laws to estimate body size is more suitable for interspecific comparative analyses than assessing intraspecific variation. Collectively, these models form the basis of the dynamic R package, “pollimetry,” which provides a comprehensive resource for allometric pollination research worldwide.

Bee and floral traits affect the characteristics of the vibrations experienced by flowers during buzz pollination.

During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here, we analysed floral vibrations produced by four closely related bumblebee taxa (Bombus spp.) on two buzz-pollinated plants species (Solanum spp.). We measured floral vibrations transmitted to the flower to establish the extent to which the mechanical properties of floral vibrations depend on bee and plant characteristics. By comparing four bee taxa visiting the same plant species, we found that peak acceleration, root mean-squared acceleration (RMS) and frequency vary between bee taxa, but that neither bee size (intertegular distance) nor flower biomass (dry mass) affects peak acceleration, RMS or frequency. A comparison of floral vibrations of two bee taxa visiting flowers of two plant species showed that, while bee species affects peak acceleration, RMS and frequency, plant species only affects acceleration (peak acceleration and RMS), not frequency. When accounting for differences in the transmission of vibrations across the two types of flower, using a species-specific 'coupling factor', we found that RMS acceleration and peak displacement do not differ between plant species. This suggests that bees produce the same initial acceleration in different plants but that transmission of these vibrations through the flower is affected by floral characteristics.

Mass-length Relationships for 3 Bee Species in Northwest Ohio

The ability to accurately estimate bee mass through measurements of intertegular distance (ITD) is an important tool for field biologists. ITD is the distance between the bases of the 2 wing tegulae on the bee’s thorax. However, the relationship between ITD and bee mass can vary based on species and sampling region. A collection of 92 bees—representing 3 species—was examined to assess the accuracy of ITD in estimating dry mass for bees in northwest Ohio. The focus was on 3 species: silky striped sweat bees (Agapostemon sericeus), honey bees (Apis mellifera), and common eastern bumble bees (Bombus impatiens). Overall, there was a positive correlation between ITD and dry mass across all individuals sampled (R2 = 0.77), but within species the degree of correlation varied significantly. The results suggest that ITD accurately estimates dry mass in silky striped sweat bees (R2 = 0.93), but the correlation weakens in common eastern bumble bees (R2 = 0.54) and is non-existent in honey bees (R2 = 0.39). Field biologists interested in using ITD to estimate bee mass should take preliminary measurements when investigating bumble bees, and should avoid ITD estimates in honey bees.