The spread of parasites is one of the primary drivers of population decline of both managed and wild bees. Several bee parasites are transmitted by the shared use of flowers, turning floral resources into potential disease hotspots. However, we know little about how floral morphology and floral species identity affect different steps of the transmission process. Here, we used the gut parasite Crithidia bombi and its primary host, bumble bees (Bombus spp.), to examine whether floral traits or species identity better predict three basic steps of parasite transmission on flowers: feces deposition on flowers, survival of the parasite on flowers, and acquisition by a new host. We also identified which traits and/or species were most strongly associated with each step in the transmission process. We found that both trait- and species-based models fit the data on deposition of feces and survival of C. bombi on flowers, but that species-based models provided a better fit compared with trait-based ones. However, trait-based models were better at predicting the acquisition of C. bombi on flowers. Although different species tended to support higher fecal deposition or parasite survival, we found that floral shape provided explanatory power for each of the transmission steps. When we assessed overall transmission potential, floral shape had the largest explanatory effect, with wider, shorter flowers promoting higher transmission. Taken together, our results highlight the importance of flower species identity and floral traits in disease transmission dynamics of bee parasites, and floral shape as an important predictor of overall transmission potential. Identifying traits associated with transmission potential may help us create seed mix that presents lower parasite transmission risk for bees for use in pollinator habitat.

Several bee parasites are transmitted through flowers, and some of them can infect multiple host species. Given the shared use of flowers by bee species, parasites can potentially encounter multiple host species, which could affect the evolution of parasite virulence. We used the trypanosomatid parasite Crithidia bombi and its host, the common eastern bumble bee (Bombus impatiens), to explore the effect of infecting an alternative host, the alfalfa leaf-cutter bee (Megachile rotundata), on parasite infectivity and ability to replicate. We conducted a serial passage experiment on primary and alternative hosts, assessing infectivity and intensity of infection during five passes. Parasite cells from each pass through the alternative host were also used to infect a group of primary hosts. We found that serial passes through the alternative host increased infectivity, but there was no effect on intensity of infection. Interestingly, both the probability and intensity of infection on the primary host increased after serial passage through the alternative host. This increase in intensity of infection could be due to maladaptation after selection of new C. bombi strains has occurred in the alternative host. This study suggests that host switching has the potential to affect the adaptation of bee parasites to their hosts.

Mason bees (Megachilidae: Osmia) are alternative managed pollinators with the potential to supplement pollination by honey bees in many crops. However, challenges for their management in orchards still remain. If nesting conditions are not optimal, females can show high dispersion rates, which decrease their economic viability at commercial scales. One way to improve female retention is by offering attractive nesting substrates. We tested the effect of several combinations of substrate materials and shelter types, as well as an attractant compound, on the retention and performance of Osmia lignaria and O. cornifrons females. We compared nesting in three types of shelter (blue and white plastic totes and brown pine plywood), with cardboard tubes of four different diameters (5–8 mm), reeds, and wood blocks as substrates at an experimental farm orchard. In a separate experiment with plywood shelters and 7‐mm cardboard tubes, we tested an attractant spray based on decanoic acid (patent number US 9301521B2), a compound isolated from O. lignaria cocoons and expected to encourage females to nest in artificial cavities. In both experiments, O. cornifrons showed higher female retention than O. lignaria. The combination of plywood shelters with reeds had the highest nesting for both species, although O. cornifrons also readily used cardboard tubes of 5–6 mm diameter. The attractant spray increased nesting by O. cornifrons, but not by O. lignaria. We also found a significant interaction between the effect of the attractant and the year of the experiment, indicating that weather and other environmental variables could affect the efficacy of the attractant. Together, our results suggest that using the right combination of shelters and substrates, as well as the attractant spray, is an effective strategy to increase Osmia female retention for orchard pollination.

Parasites are commonly cited as one of the causes of population declines for both managed and wild bees. Epidemiological models sometimes assume that increasing the proportion of infected individuals in a group should increase transmission. However, social insects exhibit behaviors and traits which can dampen the link between parasite pressure and disease spread. Understanding patterns of parasite transmission within colonies of social bees has important implications for how to control diseases within those colonies, and potentially the broader pollinator community. We used bumble bees (Bombus impatiens Cresson) (Hymenoptera: Apidae) and western honey bees (Apis mellifera L.) (Hymenoptera: Apidae) infected with the gut parasites Crithidia bombi (Lipa & Triggiani) (Trypanosomatida: Trypanosomatidae) and Nosema ceranae (Fries et al.) (Dissociodihaplophasida: Nosematidae), respectively, to understand how the initial proportion of infected individuals impacts within-colony spread and intensity of infection of the parasites. In bumble bees, we found that higher initial parasite prevalence increased both the final prevalence and intensity of infection of C. bombi. In honey bees, higher initial prevalence increased the intensity of infection in individual bees, but not the final prevalence of N. ceranae. Measures that reduce the probability of workers bringing parasites back to the nest may have implications for how to control transmission and/or severity of infection and disease outbreaks, which could also have important consequences for controlling disease spread back into the broader bee community.

Abstract Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts – including four managed species – from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.

The blue orchard bee, Osmia lignaria (Say) (Hymenoptera: Megachilidae), is an alternative managed pollinator of rosaceous tree-crops, and potentially could be used for blueberry (Ericaceae) pollination. However, the floral preferences of this species for other types of flowers could prevent them from visiting blueberry flowers when alternative forage is available.To evaluate O. lignaria suitability for pollination of commercial blueberries in Michigan, we identified the main pollen sources in scopal loads and brood provisions, and determined the contribution of blueberry pollen to pollen collected by females nesting inside or at the border of a large blueberry field. Across two bloom seasons, we found that blueberry pollen was not the most abundant pollen type in either the scopal loads (approximate to 6%) or the brood provisions (13-20%). Black cherry (Prunus serotina, Rosaceae), white clover (Trifolium repens, Fabaceae), and red clover ( Trifolium pratese, Fabaceae) were the most abundant pollen types in the brood provisions. While shelter location (inside or at the border of the field) had an influence on the use of some of these plants, it did not affect the use of blueberry pollen. Our results indicate that in these field conditions, O. lignaria visit other plants rather than blueberries as a pollen source, making it poorly suited as an alternative managed pollinator for this specific crop.

Osmia lignaria and O. cornifrons require mineral soil to build partitions between cells in their nests. We examined the textures of soil collected by these bees, using laser particle size analysis. For both species, soil in the nest was generally loam or sandy loam in texture, although individual partitions had wide variation in particle size. Partitions in O. cornifrons nests had 5.8% higher clay content than those in O. lignaria nests. Textural trends were similar when data from individual partitions were analyzed. For both species, we found no significant effect of nearby soil texture or the position of the partition in the nest, on the texture of individual partitions. Observations of partitions indicate that some females collect soil material from different locations to build one single partition. These results shed new light on the ecology of soil used by cavity nesting mason bees, with implications for their management as alternative pollinators.

Thygater aethiops is a native bee that can be found in parks and gardens in diverse urban areas such as those in the city of Bogotá (Colombia). However, little is known about its biology as well as ecological adaptations to urban areas. This study aimed to describe the seasonal cycle and daily foraging activities of T. aethiops, as well as identify the pollen resources used by this bee over a year in a population nesting in an aggregation in the “Parque Nacional Enrique Olaya Herrera” in Bogotá. Changes in the nest activity were monitored weekly by counting the number of active nests in the aggregation between December/2012 and February/2014. To determine the daily foraging activity, the numbers of bees entering their nests over a period of 10 minutes every hour between 8:00 and 14:00 h were recorded. Females with pollen loads entering to their nest were captured weekly, between September/2012 and August/2013, and their pollen loads analyzed. Three nesting peaks occurred after the precipitation peaks, but the number of active nests was not correlated with precipitation. The nesting activities stopped in a large number of the active nests (20-50 % of nests) after an anthropic disturbance was registered in the nesting area. Bees forage for nectar and pollen between 8:00 and 14:00 h, with a peak at 10:00 h. Daily foraging activity changed during the study period due to anthropic disturbance. There was not a significant relationship between air temperature and the number of females entering their nests. Foraging activities did not change between the dry and rainy seasons. A total of 26 pollen types were found in 169 pollen loads. Ulex europaeus (Fabaceae) and Solanum laxum (Solanaceae) were the most abundant plants represented on the pollen load across the study period. According to these results, T. aethiops would be considered a mesolectic species. The ability of T. aethiops to use different pollen resources both native and exotic, as well as to presumably recover its population after disturbances, are characteristics that may have allowed this bee to adapt to urban environments. Knowledge on the floral resources as well as other biological features of this bee species is important to promote its conservation in urban areas.

RESUMEN Bombus atratus es una especie nativa de Sur América de la cual se han estudiado aspectos de cría y manejo para polinización, y actualmente se están desarrollando metodologías para implementarla como polinizador comercial. Por esta razón, el objetivo de éste estudio fue comparar la longevidad de las obreras y el desarrollo de las colonias en diferentes condiciones ambientales: campo abierto (pastizales), invernadero y cámara de cría. Fueron usadas dos colonias en cada ambiente, todas las obreras fueron marcadas y semanalmente se revisaron las colonias para registrar el número de obreras. Los resultados muestran que la longevidad de las obreras que se encontraban en campo abierto (12 ± 4 días) e invernadero (15 ± 6 días) es significativamente menores que la de las obreras ubicadas en la cámara de cría (54 ± 20 días). El desarrollo de las colonias en campo abierto e invernadero en cuanto a producción de obreras fue similar, y presentaron menor número de obreras que las colonias en cámara de cría. La disminución en la longevidad de las obreras en campo abierto e invernadero puede estar influenciada por factores ambientales relacionados con la ubicación de las colonias, parasitismo o depredación, desgaste por forrajeo y la disponibilidad de recursos en la zona. La alta mortalidad de obreras durante las primeras semanas puede ser un factor limitante para el éxito de las colonias. Se discuten posibles métodos para incrementar el éxito de adaptación de las colonias. Palabras clave: abejas nativas, cría de abejorros, manejo de colonias. ABSTRACT Bombus atratus is a native species from South America which has been studied for breeding and management for pollination, and methodologies are currently being developed to use it as a commercial pollinator. For this reason, the aim of the study was to compare the worker’s longevity and colony development under different environments: open field (grassland), greenhouse, and brood chamber. Two colonies were used in each environment, all workers were labeled and colonies were checked weekly for the number of workers. Results show that worker’s longevity in open field (12 ± 4 days) and greenhouse (15 ± 6 days) is significantly less than the worker’s longevity in the brood chamber (54 ± 20 days). Colony development in open field and greenhouse regarding number of workers were similar, with fewer workers than the colonies in the brood chamber. The decrease in worker’s longevity in open field and greenhouse may be due to the influence of environmental factors related with the location of the colonies, parasitism or predation, foraging, and the resources availability in the area. The workers high mortality during the first weeks can be a limiting factor for the colonies success. Possible methods to increase the colonies adaptation success are discussed. Keywords:

Bombus atratus is a native species from South America which has been studied for breeding and management for pollination, and methodologies are currently being developed to use it as a commercial pollinator. For this reason, the aim of the study was to compare the worker's longevity and colony development under different environments: open field (grassland), greenhouse, and brood chamber. Two colonies were used in each environment, all workers were labeled and colonies were checked weekly for the number of workers. Results show that worker's longevity in open field (12 +/- 4 days) and greenhouse (15 +/- 6 days) is significantly less than the worker's longevity in the brood chamber (54 +/- 20 days). Colony development in open field and greenhouse regarding number of workers were similar, with fewer workers than the colonies in the brood chamber. The decrease in worker's longevity in open field and greenhouse may be due to the influence of environmental factors related with the location of the colonies, parasitism or predation, foraging, and the resources availability in the area. The workers high mortality during the first weeks can be a limiting factor for the colonies success. Possible methods to increase the colonies adaptation success are discussed.

Thygater aethiops is a native bee that can be found in parks and gardens in diverse urban areas such as those in the city of Bogotá (Colombia). However, little is known about its biology as well as ecological adaptations to urban areas. This study aimed to describe the seasonal cycle and daily foraging activities of T. aethiops, as well as identify the pollen resources used by this bee over a year in a population nesting in an aggregation in the “Parque Nacional Enrique Olaya Herrera” in Bogotá. Changes in the nest activity were monitored weekly by counting the number of active nests in the aggregation between December/2012 and February/2014. To determine the daily foraging activity, the numbers of bees entering their nests over a period of 10 minutes every hour between 8:00 and 14:00 h were recorded. Females with pollen loads entering to their nest were captured weekly, between September/2012 and August/2013, and their pollen loads analyzed. Three nesting peaks occurred after the precipitation peaks, but the number of active nests was not correlated with precipitation. The nesting activities stopped in a large number of the active nests (20-50 % of nests) after an anthropic disturbance was registered in the nesting area. Bees forage for nectar and pollen between 8:00 and 14:00 h, with a peak at 10:00 h. Daily foraging activity changed during the study period due to anthropic disturbance. There was not a significant relationship between air temperature and the number of females entering their nests. Foraging activities did not change between the dry and rainy seasons. A total of 26 pollen types were found in 169 pollen loads. Ulex europaeus (Fabaceae) and Solanum laxum (Solanaceae) were the most abundant plants represented on the pollen load across the study period. According to these results, T. aethiops would be considered a mesolectic species. The ability of T. aethiops to use different pollen resources both native and exotic, as well as to presumably recover its population after disturbances, are characteristics that may have allowed this bee to adapt to urban environments. Knowledge on the floral resources as well as other biological features of this bee species is important to promote its conservation in urban areas.

Andean blueberry ( Vaccinium meridionale ) is a native plant from South America with a high potential for national and international use. The aim of this study was to identify the floral visitors and potential pollinators of the Andean blueberry in two growing areas. The study was done in four samplings areas distributed in Guachetá (Cundinamarca), Ráquira and San Miguel de Sema (Boyacá) during the first blooming season of 2012. The floral visitors were recorded between 06:00 and 17:00 h, visitors behavior was recorded and pollen samples obtained from their bodies. The Pollination Probability Index (PPI) of the main visitors was calculated, and also the contribution to the pollination service through the Pollination Importance Index (PII). A total of 11 insect species was identified visiting Andean blueberry, of which Apis mellifera , Bombus hortulanus and B. rubicundus were the most frequently in all sampling areas. Both species of Bombus vibrate flowers to remove pollen, been B. hortulanus the visitor that transported the most Andean blueberry pollen. Apis mellifera visits flowers to gather nectar, but it can also transport Andean blueberry pollen. The contribution of the main visitors to the Andean blueberry pollination varies between sampling areas, been highest the contribution of A. mellifera in Guacheta-Ráquira, and the B. hortulanus in San Miguel de Sema.

The carpenter bees of the genus Xylocopa are some of the most efficient pollinators of many plants of the genus Passiflora and for this reason the use of “trap nest” has been proposed to increase the number of visits of these pollinators. The aim of this study was to establish the floral visitors diversity and pollination level in granadilla (Passiflora ligularis ), purple passion fruit (Passiflora edulis f. edulis) and yellow passion fruit (Passiflora edulis f. flavicarpa ) crops, as well as explore the viability of breeding Xylocopa using trap nest. In each crop the frequency of visits of Xylocopa and other insects in two blooms were assessed, as well as fruit set and fruit characteristics. Trap nests of bamboo canes and eucalyptus logs were used. Results showed that in the purple passion fruit crop the fruit set is high despite the low frequency of Xylocopa visits, while in the granadilla and yellow passion fruit crops the fruit set could be increased. We found that Xylocopa only nested in bamboo canes in the yellow passion fruit crop, but with low success. We discuss the possible reasons for this and propose guidelines for future Xylocopa trap nest studies in Colombia. The first description of Xylocopa nasica nests in bamboo canes is made.

Andean blueberry (Vaccinium meridionale) is a native plant from South America with a high potential for national and international use. The aim of this study was to identify the floral visitors and potential pollinators of the Andean blueberry in two growing areas. The study was done in four samplings areas distributed in Guacheta (Cundinamarca), Raquira and San Miguel de Sema (Boyaca) during the first blooming season of 2012. The floral visitors were recorded between 06:00 and 17:00 h, visitors behavior was recorded and pollen samples obtained from their bodies. The Pollination Probability Index (PPI) of the main visitors was calculated, and also the contribution to the pollination service through the Pollination Importance Index (PII). A total of 11 insect species was identified visiting Andean blueberry, of which Apis mellifera, Bombus hortulanus and B. rubicundus were the most frequently in all sampling areas. Both species of Bombus vibrate flowers to remove pollen, been B. hortulanus the visitor that transported the most Andean blueberry pollen. Apis mellifera visits flowers to gather nectar, but it can also transport Andean blueberry pollen. The contribution of the main visitors to the Andean blueberry pollination varies between sampling areas, been highest the contribution of A. mellifera in Guacheta-Raquira, and the B. hortulanus in San Miguel de Sema.