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Agricultural expansion and intensification negatively affect pollinator populations and has led to reductions in pollination services across multiple cropping systems. As a result, growers and researchers have utilized the restoration of local and landscape habitat diversity to support pollinators, and wild bees in particular. Although a majority of studies to date have focussed on effects in pollinator-dependent crops such as almond, tomato, sunflower, and watermelon, supporting wild bees in self-pollinated crops, such as grapes, can contribute to broader conservation goals as well as provide other indirect benefits to growers. This study evaluates the influence of summer flowering cover crops and landscape diversity on the abundance and diversity of vineyard bee populations. We showed that diversity and abundance of wild bees were increased on the flowering cover crop, but were unaffected by changes in landscape diversity. These findings indicate that summer flowering cover crops can be used to support wild bees and this could be a useful strategy for grape growers interested in pollinator conservation as part of a broader farmscape sustainability agenda.

Supporting ecosystem services and conserving biodiversity may be compatible goals, but there is concern that service-focused interventions mostly benefit a few common species. We use a spatially replicated, multiyear experiment in four agricultural settings to test if enhancing habitat adjacent to crops increases wild bee diversity and abundance on and off crops. We found that enhanced field edges harbored more taxonomically and functionally abundant, diverse, and compositionally different bee communities compared to control edges. Enhancements did not increase the abundance or diversity of bees visiting crops, indicating that the supply of pollination services was unchanged following enhancement. We find that actions to promote crop pollination improve multiple dimensions of biodiversity, underscoring their conservation value, but these benefits may not be spilling over to crops. More work is needed to identify the conditions that promote effective co-management of biodiversity and ecosystem services.

Bees visit native and non-native plant species for pollen and nectar resources in urban, agricultural, and wildland environments. Results of an extensive survey of bee-flower collection records from 10 California cities from 2005-2011 were used to examine host-plant records of native and non-native ornamental plants to diverse native and non-native bee species; five cities were from northern California and five were from southern California. A total of 7,659 bees and their floral host plants were examined. Of these, 179 were Apis mellifera and 7,390 were non- Apis . Only four other non- native species (all in Megachilidae) were recorded in the survey, and together they accounted for 402 individuals. These bees have been databased in preparation for deposition in the University of California-Berkeley Essig Museum of Entomology. We identified 229 bee species and 42 genera visiting native and non-native plant types in urban areas. Of the 229 species, 71 bee species were collected from only native plants; 52 were collected from only non-native host plants; and 106 were collected from both types of plants. Native bee species were common on native plants and non-native plants, but there were substantially more non-native bee species visiting non-native plants compared to native plants. Flowering periods in months were similar for both types of plants, but non-natives tended to flower later in the year. We propose that using native and non-native plants improves habitat gardening by increasing opportunities for attracting a richer diversity of bee species and for longer periods. Knowing basic bee-flower relationships in an area is key to planning a bee habitat garden with a variety of plant types, regardless of their geographic origin. !!NOTE! Supplementary files can be found in the left menu (article tools)!!

Emergent fungal diseases are critical factors in global biodiversity declines. The fungal pathogenNosema bombiwas recently found to be widespread in declining species of North American bumble bees (Bombus), with circumstantial evidence suggesting an exotic introduction from Europe. This interpretation has been hampered by a lack of knowledge of global genetic variation, geographic origin, and changing prevalence patterns ofN. bombiin declining North American populations. Thus, the temporal and spatial emergence ofN. bombiand its potential role in bumble bee decline remain speculative. We analyzeNosemaprevalence and genetic variation in the United States and Europe from 1980, before an alleged introduction in the early 1990s, to 2011, extractingNosemaDNA fromBombusnatural history collection specimens from across this time period.Nosema bombiprevalence increased significantly from low detectable frequency in the 1980s to significantly higher frequency in the mid- to late-1990s, corresponding to a period of reported massive infectious outbreak ofN. bombiin commercial bumble bee rearing stocks in North America. Despite the increased frequency, we find no conclusive evidence of an exoticN. bombiorigin based on genetic analysis of globalNosemapopulations; the widespreadNosemastrain found currently in declining United States bumble bees was present in the United States before commercial colony trade. Notably, the USN. bombiis not detectably different from that found predominantly throughout Western Europe, with both regions characterized by low genetic diversity compared with high levels of diversity found in Asia, where commercial bee breeding activities are low or nonexistent.

Fire has a major impact on the structure and function of many ecosystems globally. Pyrodiversity, the diversity of fires within a region (where diversity is based on fire characteristics such as extent, severity, and frequency), has been hypothesized to promote biodiversity, but changing climate and land management practices have eroded pyrodiversity. To assess whether changes in pyrodiversity will have impacts on ecological communities, we must first understand the mechanisms that might enable pyrodiversity to sustain biodiversity, and how such changes might interact with other disturbances such as drought. Focusing on plant-pollinator communities in mixed-conifer forest with frequent fire in Yosemite National Park, California, we examine how pyrodiversity, combined with drought intensity, influences those communities. We find that pyrodiversity is positively related to the richness of the pollinators, flowering plants, and plant-pollinator interactions. On average, a 5% increase in pyrodiversity led to the gain of approximately one pollinator and one flowering plant species and nearly two interactions. We also find that a diversity of fire characteristics contributes to the spatial heterogeneity (β-diversity) of plant and pollinator communities. Lastly, we find evidence that fire diversity buffers pollinator communities against the effects of drought-induced floral resource scarcity. Fire diversity is thus important for the maintenance of flowering plant and pollinator diversity and predicted shifts in fire regimes to include less pyrodiversity compounded with increasing drought occurrence will negatively influence the richness of these communities in this and other forested ecosystems. In addition, lower heterogeneity of fire severity may act to reduce spatial turnover of plant-pollinator communities. The heterogeneity of community composition is a primary determinant of the total species diversity present in a landscape, and thus, lower pyrodiversity may negatively affect the richness of plant-pollinator communities across large spatial scales.

The purpose of this article is to challenge organizational scholars, management educators, and business leaders to consider more deeply the impact of global business activities on local ecosystems. Drawing on the management, sustainability, and entomology literature, we illustrate the complex relationship between global business and biodiversity loss through the lens of the commercial bumble bee trade. Global firms in this trade rear and supply bees for greenhouse crop pollination. We build on a well-known global strategy framework used in management education by adding a sustainability dimension, and offering propositions for the relationship between global business strategy and the strength of environmental sustainability. We conclude that a locally responsive, place-sensitive business strategy supports the strongest degree of environmental sustainability, and addresses the invisible compromises to ecosystem health that may result from the efforts of global firms to provide otherwise beneficial products and services.

In 2009 the USDA-NRCS asked the Urban Bee Lab at the University of California, Berkeley if urban bee-flower knowledge could be used to attract native bees to farms in Brentwood, Contra Costa Co. in Northern California. The overarching question was, could native bees play a role in supplementing honey bees by providing pollination services for crop flowers? If so, how many native bee species were visiting farms and how frequently did they occur?Eight small farms (4-60 ha) were selected to investigate this question; four were control and four were treatment farms where bee habitat gardens were constructed. Habitat gardens were stocked with native and non-native ornamental plants known to attract native bees (and honey bees).Bees were monitored yearly in spring at each farm from 2010-2016 to evaluate species richness and abundance, which yielded several findings:I. Farms near urban areas and a creek were consistently more attractive to diverse and abundant bee speciesII. Inconsistent bee garden maintenance and major changes in farm operations in other farms resulted in consistently lower measurements of bee richness and abundanceIII. Over the seven-year monitoring period, 144 bee species were recorded among all farmsIV. Nearby urban areas had most of the same species as the agricultural areas, suggesting a relationship of bees moving between two areasV. A total of 23 diverse native bee species were recorded from apple, berry, and cherry flowers, and many of them in substantial numbers, indicating that native bees were providing pollination servicesFinally, maintaining frequent professional contact with growers was considered crucial in conducting research over the long term. These contacts were also critical in designing outreach packages to growers who expressed interest in applying our native bee findings to their farming operations.

There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.

Native bees are important ecologically and economically because their role as pollinators fulfills a vital ecosystem service. Pollinators are declining due to various factors, including habitat degradation and destruction. Grasslands, an important habitat for native bees, are particularly vulnerable. One highly imperiled and understudied grassland type in the United States is the Pacific Northwest Bunchgrass Prairie. No studies have examined native bee communities in this prairie type. To fill this gap, the bee fauna of the Zumwalt Prairie, a large, relatively intact remnant of the Pacific Northwest Bunchgrass Prairie, was examined. Native bees were sampled during the summers of 2007 and 2008 in sixteen 40-ha study pastures on a plateau in northeastern Oregon, using a sampling method not previously used in grassland studies—blue vane traps. This grassland habitat contained an abundant and diverse community of native bees that experienced marked seasonal and inter-annual variation, which appears to be related to weather and plant phenology. Temporal variability evident over the entire study area was also reflected at the individual trap level, indicating a consistent response across the spatial scale of the study. These results demonstrate that temporal variability in bee communities can have important implications for long-term monitoring protocols. In addition, the blue vane trap method appears to be well-suited for studies of native bees in large expanses of grasslands or other open habitats, and may be a useful tool for monitoring native bee communities in these systems.

Pathogens have been implicated as potential factors in the recent decline of some North American bumble bee (Bombus) species, but little information has been reported about the natural enemy complex of bumble bees in the United States. We targeted bumble bee populations in a state-wide survey in Illinois and several sites in California and Oregon where declines have been reported to determine presence and prevalence of natural enemies. Based on our observations, most parasites and pathogens appear to be widespread generalists among bumble bee species, but susceptibility to some natural enemies appeared to vary.

Concerns about pollinator declines have grown in recent years, yet the ability to detect changes in abundance, taxonomic richness, and composition of pollinator communities is hampered severely by the lack of data over space and time. Citizen scientists may be able to extend the spatial and temporal extent of pollinator monitoring programs. We developed a citizen-science monitoring protocol in which we trained 13 citizen scientists to observe and classify floral visitors at the resolution of orders or super families (e.g., bee, wasp, fly) and at finer resolution within bees (superfamily Apoidea) only. We evaluated the protocol by comparing data collected simultaneously at 17 sites by citizen scientists (observational data set) and by professionals (specimen-based data set). The sites differed with respect to the presence and age of hedgerows planted to improve habitat quality for pollinators. We found significant, positive correlations among the two data sets for higher level taxonomic composition, honey bee (Apis mellifera) abundance, non-Apis bee abundance, bee richness, and bee community similarity. Results for both data sets also showed similar trends (or lack thereof) in these metrics among sites differing in the presence and age of hedgerows. Nevertheless, citizen scientists did not observe approximately half of the bee groups collected by professional scientists at the same sites. Thus, the utility of citizen-science observational data may be restricted to detection of community- level changes in abundance, richness, or similarity over space and time, and citizen-science observations may not reliably reflect the abundance or frequency of occurrence of specific pollinator species or groups.

Evidence is mounting that pollinators of crop and wildland plants are declining worldwide. Our research group at UC Berkeley and UC Davis conducted a 3-year survey of bee pollinators in seven cities from Northern California to Southern California. Results indicate that many types of urban residential gardens provide floral and nesting resources for the reproduction and survival of bees, especially a diversity of native bees. Habitat gardening for bees, using targeted ornamental plants, can predictably increase bee diversity and abundance, and provide clear pollination benefits.

The potential pollinators of yellow starthistle (Centaurea solstitialis) were surveyed at six sites in north-eastern Oregon, USA, between May and September from 2000 to 2002. The objective of the study was to determine the species composition and relative abundance of the insects that visited yellow starthistle throughout the flowering season and to assess the pollen loads on their bodies in order to infer which species might be the most effective pollinators of this invasive plant species in north-eastern Oregon. A total of 1923 individual flower visitors were collected at the six sites over the 3 year study period, comprising four orders, 41 families, and 203 species of insects. The 20 most commonly collected species represented nearly 59% of the individuals and just ten of these species could be considered the key pollinators, judging by the combination of abundance and pollen carriage (the megachilids, Megachile apicalis (introduced) and Megachile perihirta, the apids, Apis mellifera (introduced), Bombus bifarius, Bombus centralis, Svastra obliqua, and Melissodes lutalenta, the halictids, Halictus tripartitus and Halictus ligatus, and the tachinid, Peleteria malleola. Over the 3 year study period, the six sites were consistently distinct in their flower visitor fauna, with the metropolitan Pendleton sites having a species composition distinct from the four mountain sites. Consistent patterns of interannual variation also were observed over the 3 year study. These patterns of flower visitation are interpreted in the context of the plant community within which yellow starthistle grows in north-eastern Oregon.

In mid 2003 a diverse floral resource was planted in a small urban residential plot at the University of California, Berkeley Oxford Tract with the goal of attracting local native California bee species to assess emerging patterns of diversity and seasonality. A standard procedure was then used in 2004 to sample the bees and monitor their host flowers. Pollen and nectar resources were abundant and consistently available during spring, summer, and early fall months of that year. Thirty-two bee species representing 17 genera, and five families used these resources through the 2004 season. Urban bees were categorized into three seasonalities: early season, late season, and full season represented by seven, eight, and 17 species respectively. Results of this study indicate that newly-planted urban gardens, which are designed for bees, have the potential to attract diverse seasonal bee taxa if diverse floral resources are provided throughout the growing season. Implications of these finding are discus...

A survey of the bee species and their ornamental host flowers that occur in residential neighborhoods of the cities of Albany and adjacent Berkeley in northern California was conducted from 1999–2003. A simple bee frequency (visitation) count was developed to evaluate the relative attraction of bees to their host flowers. Results of the survey revealed that 76 species of bees, mostly natives, from five families, visited 129 host plants at measurable levels. The most common host plant families were Asteraceae, Lamiaceae, Polygonaceae, Rosaceae, and Scrophulariaceae. Honey bees and all other bee taxa were recorded separately on host plants, and both bee groups were more attracted to California native plants than exotics on a percentage basis. Variable attraction was recorded within native and exotic host plants, and a large part of this variation appears related to where the plants are found in residential areas. In general, the highest bee diversity and abundance was observed in diverse gardens ha...

The subgenus Onagrandrena was first recognized and described by Linsley and MacSwain (1956) to include those black Andrena that are oligolectic on plants of the family Onagraceae and have pollen-collecting hairs modified to collect the specialized pollen from those plants. The males are more difficult to recognize than the females and most males are very similar to those of Melandrena. Since first described, two species of Onagrandrena have been recognized that have pale vestiture in both sexes. However, the pollen collecting hairs of both of these are of the Onagrandrena type, both sexes have well-formed pronotal angles and lateral ridges, and the males have relatively narrow, long mandibles with reduced or absent subapical teeth. The species of Onagrandrena are very similar and are difficult to tell apart. Populations seem to be relatively isolated in desert locations with habitats amenable to the host plants. This, we believe, has led to a proliferation of species and we can detect slight average differences between populations from different geographic locations within some species. A few of these microgeographic races have been recognized in the literature as subspecies, but the present authors prefer not to formally recognize these races with names. The reader is referred to earlier sections of this revision (LaBerge l967, l969, l97l, 1973, l977, l980, l986, l989; LaBerge and Bouseman 1970, 1987; LaBerge and Ribble 1972, 1975; Bouseman and LaBerge 1979; Thorp, 1969; Donovan, 1977) for details of morphology and for a more complete bibliography of the literature on Andrena. No new morphological terms have been introduced in the present work and the bibliography presented includes only references cited in the text or not listed in earlier parts of the revision. Published locality and floral records are included in the appropriate sections near the end of each species account. Maps showing the known distributions of species (Figs. 2-6) do not have all listed localities spotted on them. Localities that could be located only in a general way, such as county, or could not be found on maps or in gazetteers are omitted. Considerable detailed information is available concerning the floral activity of several species of Onagrandrena in papers by Linsley, MacSwain, Raven and Thorp (1963a and b, 1964) and MacSwain, Raven, and Thorp (1973). These papers also provide brief notes on nesting burrows and an earlier paper by Linsley, MacSwain and Smith (1955) gives details on the nesting biology of a few species of Onagrandrena.

Managing ecosystem services is critical to human survival, yet we do not know how large natural areas must be to support these services. We investigated how crop pollination services provided by native, unmanaged, bee communities varied on organic and conventional farms situated along a gradient of isolation from natural habitat. Pollination services from native bees were significantly, positively related to the proportion of upland natural habitat in the vicinity of farm sites, but not to any other factor studied, including farm type, insecticide usage, field size and honeybee abundance. The scale of this relationship matched bee foraging ranges. Stability and predictability of pollination services also increased with increasing natural habitat area. This strong relationship between natural habitat area and pollination services was robust over space and time, allowing prediction of the area needed to produce a given level of pollination services by wild bees within this landscape.

Author(s): Forrest, JRK; Thorp, RW; Kremen, C; Williams, NM | Abstract: Land-use change frequently reduces local species diversity. Species losses will often result in loss of trait diversity, with likely consequences for community functioning. However, the converse need not be generally true: management approaches that succeed in retaining species richness could nevertheless fail to maintain trait diversity. We evaluated this possibility using bee communities in a California agroecosystem. We examined among site patterns in bee species diversity and functional-trait diversity in a landscape composed of a mosaic of semi-natural habitat, organic farms and conventional farms. We sampled bees from all three habitat types and compiled a data base of life-history ('functional') traits for each species. Although species richness was higher on organic farms than conventional farms, functional diversity was lower in both farm types than in natural habitat. Nesting location (below-ground vs. above-ground) was the primary trait contributing to differences in functional diversity between farms and natural habitat, reflecting observed differences in availability of nesting substrates among habitat types. Other traits, including phenology and sociality, were also associated with species' occurrences or dominance in particular site types. These patterns suggest that management practices common to all farms act as environmental filters that cause similarly low functional diversity in their bee communities. Synthesis and applications. Although our results support the value of organic farming in maintaining abundant and species-rich bee communities, components of bee functional diversity are not well supported in farmed landscapes, regardless of farming practice. Maintenance of natural habitat, and/or the addition of natural habitat elements to farms, is therefore important for the retention of functionally diverse bee assemblages in agroecosystems. Although our results support the value of organic farming in maintaining abundant and species-rich bee communities, components of bee functional diversity are not well supported in farmed landscapes, regardless of farming practice. Maintenance of natural habitat, and/or the addition of natural habitat elements to farms, is therefore important for the retention of functionally diverse bee assemblages in agroecosystems.

© 2015 Macmillan Publishers Limited. All rights reserved. There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.

Ecosystem services are critical to human survival; in selected cases, maintaining these services provides a powerful argument for conserving biodiversity. Yet, the ecological and economic underpinnings of most services are poorly understood, impeding their conservation and management. For centuries, farmers have imported colonies of European honey bees ( Apis mellifera ) to fields and orchards for pollination services. These colonies are becoming increasingly scarce, however, because of diseases, pesticides, and other impacts. Native bee communities also provide pollination services, but the amount they provide and how this varies with land management practices are unknown. Here, we document the individual species and aggregate community contributions of native bees to crop pollination, on farms that varied both in their proximity to natural habitat and management type (organic versus conventional). On organic farms near natural habitat, we found that native bee communities could provide full pollination services even for a crop with heavy pollination requirements (e.g., watermelon, Citrullus lanatus ), without the intervention of managed honey bees. All other farms, however, experienced greatly reduced diversity and abundance of native bees, resulting in insufficient pollination services from native bees alone. We found that diversity was essential for sustaining the service, because of year-to-year variation in community composition. Continued degradation of the agro-natural landscape will destroy this “free” service, but conservation and restoration of bee habitat are potentially viable economic alternatives for reducing dependence on managed honey bees.

We examined the role of nonnative honey bees (Apis mellifera) as pollinators of the invasive, nonnative plant species yellow star-thistle (Centaurea solstitialis), both introduced to the western United States in the early to middle 1800s. Using four different treatments (three exclosure types) at flower heads, we observed visitation rates of different pollinators. Honey bees were the most common visitors at each of three transects established at three study locales in California: University of California at Davis, Cosumnes River Preserve, and Santa Cruz Island. A significant correlation existed between honey bee visitation levels monitored in all these transects and the average number of viable seeds per seed head for the same transects. Selective exclusion of honey bees at flower heads using a 3 mm diameter mesh significantly reduced seed set per seed head at all locales. Seed set depression was less dramatic at the island locale because of high visitation rates by generalist halictid bees Augochlorella ...

Summary 1. Pan traps or water traps have been used widely to sample agricultural insect pests, but no formal studies have assessed the utility of these traps as sampling devices for bees. 2. Coloured pan traps, used as flower models, can efficiently and selectively sample an oligolectic bee, Andrena (Hesperandrena) limnanthis, and other bees associated with white-flowered Limnanthes douglasii rosea. 3. Females and males of A. limnanthis unexpectedly exhibit different colour preferences. Females are strongly attracted to white and blue traps, but discriminate against yellow traps. Males prefer white traps over blue and yellow traps. Consequently, blue traps are selective for females only, while white traps are selective for both sexes. 4. Non-A. limnanthis bees were caught in significantly greater numbers in yellow than in blue or white traps. These bees included generalists, as well as specialists that are oligolectic on mostly yellow-flowered species. 5. Colour of traps had a significant effect on the numbers of A. limnanthis females and males, and non-A. limnanthis bees caught in traps. These results indicate that quantitative sampling of bees by pan trap methods can be highly sensitive to trap colour.

The long-term goal of this study was to use solitary bees to assess the impact of advancing Africanized honey bees (Apis mellifcra scutcllata Lepeletier) on the native California bee fauna. Cavity-nesting, solitary bee species were systematically monitored in wooden trap nests at 6 sites in northern central California from 1990 to 1992. Three sites were in the San Joaquin Valley in wildlife refuges or preserves; 3 were in coastal mountain or Sierran foothill parks or reserves. Differences in frequencies of nesting bees were observed and recorded among sites and habitats through time. A Poisson regression indicated that all explanatory variables and their 1st order interactions were highly significant. There were significant differences among bee taxa, sites and years, and their interactions (bee X site; bee X year; site X year). Mcgachile species were the predominant cavity nesters in the 3 valley sites; Osmia species were the common group in coastal mountain I foothill sites. In a computer simulation, using a variation of the Poisson regression, several significant differences were also observed between yearly frequency counts for certain bee species at the same site. Possible reasons for year to year changes included differential natural mortality, extreme annual weather patterns, use of marginal habitats, and negative impacts from exotic solitary bee species. Three exotic megachilids (Mcgachile rotundata (F.), M. apicalis Spinola, and M. concinna Smith) have successfully invaded and become established in California. Possibly, M. apicalis has affected other cavity nesting bee species, including the exotic M. rotundata in our Central Valley sites.

Temporal and spatial characteristics of a community of cavity nesting megachilid bee species and their introduced competitors were examined at a site in the Central Valley of California. Two of the introduced bee species, Megachile apicalis Spinola and Megachile rotundata (F.), were frequent nest site occupants and accounted for 19.6 and 3.4% of all artificial nesting cavities (trap-nests) monitored during the 1st and 2nd yr of this study, respectively. These species were most active before and after the peak in native bee nesting activity and tended to occupy xeric habitats, despite significantly higher larval mortality associated with such environments. The ability to occupy a wide array of habitats may account for the invasion success of M. apicalis in California. Another invader, the European earwig, Forficula auricularia L., was a frequent occupant of nesting cavities in mesic habitats, accounting for 59 and 85% occupancy of trap-nests during the 1st and 2nd yr of the study, respectively. Exclusion experiments indicate earwig densities were sufficient to displace female bees at nest sites with 113 as much nesting activity occurring in sampling units that allowed entry by earwigs as those made inaccessible to them with sticky barriers. In comparison, all native species (including bees and wasps) never accounted for >25% of all occupied nesting cavities of either monitoring period of the study.

High and low pollen-hoarding strains of honey bees were selected based on quantity of pollen stored in combs. Performance of strains in commercial alfalfa seed pollination is reported. After three generations of selection, colonies with instrumentally inseminated high-strain queens stored significantly more pollen (2.4-fold) than low-strain colonies. Similarly, colonies from naturally mated, outcrossed high-strain queens stored more pollen (2.4-fold) than outcrossed low-strain colonies. Selection did not change preferences for sources of pollen. After four generations of selection, colonies with naturally mated high-strain queens outcrossed with commercial drones stored significantly more pollen (l.4-fold) than commercial colonies. Rates of queen acceptance (54 and 61%) and overwintering survival (61%) in commercially managed colonies were surprisingly low, indicating 37% queen survival during a 10-mo period. Overwintered outcrossed high-strain colonies were more populous than commercial colonies at the beginning of almond bloom.

Summary 1. Global declines in honeybees have led to concerns about negative impacts on food production because of low levels of pollination. This is exemplified in California where the demand for honeybees Apis mellifera to pollinate almond Prunus dulcis is increasing, but problems with honeybee health suggest it may not be sustainable to rely solely on the pollination service of a single species. 2. We investigated the effect of the quantity of surrounding natural habitat, organic management and strips of semi-natural vegetation on flower visitation frequency of wild and managed pollinators and fruit set in 23 California almond orchards (15 conventional, 8 organic). Five conventional and four organic orchards were surrounded by a low percentage ( 30%). A further five conventional orchards with a low percentage of surrounding natural habitat had an adjacent strip of semi-natural vegetation and were included in the study to represent a realistic option for orchard management in intensive agricultural landscapes. 3. Wild bee species visited almond flowers but only in orchards with adjacent semi-natural habitat or vegetation strips. Organic management increased the flower visitation frequencies of hover flies and wild bees. The presence of a strip of semi-natural vegetation in orchards with a low percentage of surrounding natural habitat increased the number of species and the flower visitation frequency by wild pollinators but only at orchard edges and not to the degree seen when natural habitat was abundant. 4. Wild bee species richness and flower visitation frequency, but not honeybee frequency, were related to fruit set. Fruit set increased with increasing percentage of natural habitat surrounding the orchards. Organic farming or the presence of a vegetation strip did not increase fruit set. 5. Synthesis and applications. The restoration of high quality habitat strips along the edges of crop fields in highly intensified agricultural landscapes should be encouraged and monitored to conserve pollinators and to determine whether benefits for agriculture can be realized. Although honeybees are the main and most important pollinating insects for many plants, wild pollinators may be necessary to ensure high fruit set. Organic farming alone will not sustain wild pollination services for almond in California.

The expected invasion of the United States by Africanized honey bees has inspired long-term studies documenting the ecological importance of native and introduced bees. Baseline data are being gathered to predict the effects of the invasion. Standardized sampling procedures and tools have been developed to monitor bee communities. The studies will provide information for developing wildland area conservation policies.

We examined stress responses and survival in developmental stages of the invasive solitary bee Megachile apicalis Spinola during two nesting seasons in the Central Valley of California to consider whether abiotic stress tolerance of its offspring contributes to this species' successful colonization of the western United States. In 2001 and 2003, artificial nesting cavities were affixed to vertical plywood boards oriented to maximize nest cavity temperature and humidity differences: one side faced south (exposed to direct sun) and the other one faced north (shaded). After several weeks of nesting activity, we measured heat shock protein 70 (HSP70) concentrations in adults and offspring on 1 d in both years and offspring survival and mortality sources in 2003. In 2001, M. apicalis showed higher HSP70 concentrations in exposed nests than in shaded nests during all developmental stages, adults and their offspring. In 2003, overall survivorship was not significantly different between treatments because exposed nests experienced high offspring mortality caused by heat stress, whereas shaded nests suffered similarly high offspring mortality because of parasitoids. In both years of our study, females preferred shaded nests over exposed nests. M. apicalis successfully reproduces in grasslands of the Central Valley of California where offspring survive hot, dry nest sites and parasitoids in sufficient numbers to inoculate new grassland habitats, unpopulated by tolerance-limited native solitary bees, with incipient populations of this bee, M. apicalis.

Publisher Summary This chapter describes the role of insects in pollination as vector. Pollination in its most basic sense is the transfer of pollen from the male sex organ (anther) to the receptive portion of the female sex organ (stigma) in flowering plants. If the transfer is successful, it leads to fertilization, production of seed, and reproduction of the plant. This process often involves some sort of external vector such as wind, water, or animals. Some flowering plants may reproduce without the aid of pollen vectors, using mechanisms such as vegetative reproduction, apomixis, or automatic selfing. Many flowering plants are adapted to insects as pollinators and provide primary rewards that attract and keep the pollen vectors returning to flowers. Rewards include nectar, pollen, lipid secretions, food bodies, scents, resins, and material for nest building. In addition to primary rewards, most insect-pollinated flowers also produce a number of cues or signals that distinguish them from other species and promote the ease by which an insect can relocate a rewarding flower, thereby encouraging the insect to move pollen from flower to flower of the same species. These signals include odors, colors, shapes, textures, and tastes. These signals are often combined into patterns that have been recognized as syndromes related to the type of pollen vector. For example, a typical butterfly-pollinated flower that would be red, have little odor, possess a landing platform, have nectar hidden at the base of a deep tube that can be reached by the long coiled butterfly proboscis, have nectar that would be high in amino acids, and have flowers that would be open during the day.

A cluster count method for estimating honey bee, Apis mellifera L., colony strength is presented in contrast to intensive frame-by-frame evaluations. Correlation coefficients between the two methods were highly significant for 5 yr. Cluster counts are recommended to growers and beekeepers involved in pollination contracts as a simple, rapid, economic evaluation method which is not excessively disruptive to the colony. The observed adult honey bee colony populations can be estimated accurately by using the derived regression equation. The relation of cluster and intensive count to the brood area is discussed.

It is well recognized that honeybees are major players in agricultural productivity through their roles in crop pollination, and are economically valuable for hive products (mostly honey), but the indirect link between honey quality and agricultural productivity is seldom voiced. Honey is a valued and revered part of human diets. It is not just a sweetener, but also has special places in culture, religion, and medicine. The value of honey rests in its reputation for purity and that value is of paramount importance to the beekeeping industry and associated value added enterprises in packing, marketing, advertising, wholesale and retail sales. If the reputation of honey as a healthy component of human diet is eroded, then the beekeeping industry becomes jeopardized. Contamination of honey by pesticide (or antibiotic) residues from applications to crops or directly to colonies of honeybees, or adulteration of honey by unscrupulous commercial interests, detracts from honey’s repute. Similarly, concerns for contamination with GMO(Genetically Modified Organisms) in the form of pollen are frequently raised (see literature review on the web; reference below). One would expect the market for honey to be adversely affected if honey’s reputation were eroded. Honey regarded as inferior in quality commands lower prices in the international market. If the market for honey were to decline, and the price to drop, there would be serious consequences to crop production in general resulting from deterioration of beekeeping as an agricultural endeavour and the consequent abandoning of the activity by beekeepers. Having spelled out the generalities in the interconnectedness between honey quality and agricultural productivity, what are the specifics within the area of pollination that relate to government and industry policies on honey purity? This report provides a short summary of the facets of pollination and beekeeping that apply, with recommendations of the stands that need to be taken to protect and assure honey quality for the sake of adequate pollinator forces for agriculture.

Maternal investment in offspring size and number differed between spring- and summer-emerging individual females of Megachile apicalis, a solitary multivoltine bee. Data from experimentally initiated female populations indicated that spring-emerging females produced a relatively large number of progeny but allocated a small amount of food to each, resulting in small progeny. Adult females of larger body sizes provisioned food at a greater rate than did smaller females, and this body-size effect was significant in spring-emerging females. The large body size of these females allowed them to increase the number of progeny produced under the abundant floral resources that occurred during the spring. Conversely, summer-emerging females produced fewer progeny under the diminishing resources for brood production, but allocated each with more food, producing larger progeny, most of which emerged in the spring of the following year. Field data using trap-nests also indicated the same pattern of seasonal offspring size allocation found in the experimental populations. This maternal investment strategy entails a trade-off between the size and number of progeny, so that the daughters upon emergence can best perform in their brood production under the seasonally variable environments where they reproduce.

Bees require pollen for their reproduction and pollen comprises the basic larval food for bees. Most bees acquire pollen passively during flower visitation, but female bees may also collect pollen actively with the aid of various structural and behavioral adaptations. Most bees have evolved adaptations to concentrate pollen into discrete loads and transport pollen back to their nests. The various structural and behavioral adaptations of female bees for acquiring and transporting pollen are the basis of this review.

Author(s): Mussen, Eric C; Thorp, Robbin W | Abstract: Honey bees are vital to growing a successful cucurbit crop. Learn about timing, optimum conditions, and contracting with a beekeeper.

Rangelands are significant providers of ecosystem services in agroecosystems world-wide. Yet few studies have investigated how different intensities of livestock grazing impact one important provider of these ecosystem services—native bees. We conducted the first large-scale manipulative study on the effect of a gradient of livestock grazing intensities on native bees in 16 40-ha pastures in the Pacific Northwest Bunchgrass Prairie. Each pasture was exposed to one of four cattle stocking rates for two years and grazing intensity was quantified by measuring utilization. We measured soil and vegetation characteristics related to floral and nesting resources as well as several metrics of the bee community. Increased grazing intensity significantly reduced vegetation structure, soil stability, and herbaceous litter and significantly increased soil compaction and bare ground. Native bees responded with changes in abundance, richness, diversity, and community composition. Responses varied with taxa and time of season. Bumble bees were sensitive to grazing intensity early in the season, showing reduced abundance, diversity, and/or richness with increased intensity, potentially because of altered foraging behavior. In contrast, sweat bees appeared unaffected by grazing. These results show that native bee taxa vary in their sensitivity to livestock grazing practices and suggest that grazing may potentially be a useful tool for managing pollination services in mosaic agroecosystems that include rangelands.

1. Pollen on stigmas and the bodies of honey-bees foraging on almond blossoms was identified in 1988 and 1989. The percentage of blossoms setting nuts also was measured with respect to a tree limb's adjacent pollen source. 2. Every honey-bee that we collected foraging on almond blossoms had selfpollen on its body and 90% or more had cross-pollen. In 1988, 60-92% of the foragers had non-almond pollen on their bodies, while in 1989 the percentages were 92-100%. 3. In 1988 there was significantly more selfand cross-pollen on foragers' bodies than non-almond pollen with the exception of 'Peerless' nectar collectors. However, in 1989 the percentages of crossand non-almond pollen were equivalent except for 'Price', and were significantly less than the percentages of self-pollen. 4. In 1988, 42-1-81-2% of the stigmas we examined had self-pollen, 36-8-68 7% had cross-pollen, and 43-7-94 0% had non-almond pollen. In 1989, 60 0-100 0% of the stigmas had self-pollen, 10-100% had cross-pollen, and 8O)0-100 0% had non-almond pollen. 5. The percentages of pollen types on stigmas did not differ significantly between limbs adjacent to trees of the same or different cultivars. In 1988 the percentages of selfand cross-pollen on stigmas were equivalent in all cultivars except 'NePlus' which had significantly more selfthan cross-pollen. In 1989 there was significantly more selfthan cross-pollen on stigmas of all cultivars except 'Price' which had equivalent amounts of both pollen types. In both years non-almond pollen occurred with equivalent or significantly higher frequencies than self-pollen. 6. Nut set on limbs adjacent to compatible pollen sources did not differ significantly from those within the same row adjacent to trees of the same cultivar (i.e. incompatible pollen sources). 7. The population of honey-bees capable of cross-pollination in almond orchards is apparently a majority of the overall honey-bee foraging population and is homogeneously distributed throughout the orchard.

Cross-pollination was tested between different genotypes ofLycopersicon pimpinellifolium in an experimental plot situated in the southerly range of the species. Rates of cross-pollination were found to be highly correlated with flower size and were related to a lesser extent with degree of stigma exsertion. Comparisons of fertility suggest that exsertion of 1.5 mm or more from the anther tube orifice interferes with automatic self-pollination, thereby increasing rates of cross-pollination. A single species ofExomalopsis (Anthophoridae), observed to visit all tested genotypes ofL. pimpinellifolium, was responsible for most of the pollination. Other species of solitary bees and other bee families participated in cross-pollination.

The rate of flight and the foraging profiles of worker honey bees, Apis mellifera L., in disposable pollination units (DPU's) and overwintered colonies were compared. Because of population decline and lower total foraging indices, approximately 1.5 to 2 times as many DPU bees were required to match the foraging activity of overwintered colonies. Low ambient temperatures appeared to restrict the flight activity of DPU bees; higher temperatures (above about 21°C) stimulated disproportionately higher flight activity from the DPU's and 4-frame colonies.

Pyrrhopappus carolinianus and Hemihalictus lustrans constitute a mutualistic association: the early morning flowering of Pyrrhopappus provides the matinal bee with a nearly exclusive pollen source, although other plants must be visited for nectar. Female Hemihalictus, the primary pollen vector, tear open the anthers and remove the pollen before it is available to other bees. The foraging behavior of the bee insures cross-pollination. The flight pattern of the bees generally restricts the pollen dispersal range. If cross-pollination fails, then autogamy results from twisting of the styles that brings the stigmas in contact with the pollen presented on the styles of other florets. Schinia mitis is an important predator of the capitulae of P. carolinia

Pollen traps that remove pollen loads from returning forager bees changed foraging patterns for hives in almond and prune orchards. Hives with traps had greater numbers of pollen foragers and higher proportions of foraging bees with pollen loads-than hives without traps. This effect was greatest before ca. 3:00 p.m. Hives with traps had less increase in capped brood and in the adult population than did hives without traps at the end of a 48-day period.

SummaryTechniques were developed for fractional analysis of undiluted microquantities of floral nectar by HPLC. Quantitative and qualitative differences are shown between almond nectar secreted by freshly opened flowers and by those a few days old; they demonstrate the reproducibility of data obtained. HPLC characterizations may thus be utilized in plant breeding, to ensure that compatible genotypes with similar spectra of volatiles and taste components are brought together when cross-pollination is essential. They may also be useful in studies of foraging behaviour of bees among plant phenotypes and genotypes.

A population of Osmia cornuta Latr. was trapped in northern Spain during 1984, transported to the United States, quarantined, exposed to various temperature regimes through summer months, and placed in California almond orchards through winter months. Results of this study demonstrated that bees overwintered in commercial almond orchards emerged in synchrony with almond bloom; gregarious nesting was expressed; immatures developed normally on provisions composed mostly of almond pollen and nectar resources; prewintering temperatures affected winter survival of parent bees; and populations that had the highest rates of winter mortality produced the fewest number of cells per emerged female.

Mean flight activity from overwintered Apis mellifera L. colonies was usually greater and the quantity of pollen trapped was well in excess of that from disposable pollination units (DPU's). However, comparisons between individual units indicated that DPU's exhibit more uniform flight activity than colonies. Data pertinent to the effect of this atypical domiciliary crowding and colony makeup on longevity, development, and certain behaviorial adaptations of the bees are included.

Andrena placida Smith nests in compacted sand cliffs near the ocean in Marin County, California. The bees are vernal and polylectic. The chromosome numbers are n = 5 (♂) and 2n = 10 (♀). Comparisons with A. erythronii Robertson reveal that the 2 species are very similar in their biological characteristics and in structural features of their postdefecating larvae, and pupae.

Pithitis smaragdula (F.) is a bright green, small carpenter bee which is widespread in the oriental region and is known to pollinate economically important plants, especially legumes and cucurbits. About 300 bees imported from Ludhiana, India, were released 10 April 1969, at Davis, California. Subsequent collecting during the 1st season confirmed that one or more generations of the bees had been reared and that Trifolium repens L. was visited for pollen. Although the overwintering bees under observation died from unknown causes, and no living bees were found in 1970, it is possible that the bees survived elsewhere. Ecological factors believed to be important in the establishment of the colony were: few natural enemies, low competition for food, high competition for nesting sites, and a cooler, drier climate than the native habitat. Future releases are planned for warmer areas in the State.

The highest unexplained mortality of immature Megachile rotundata (F.) occurs in alfalfa-seed fields. Water-soluble saponins from alfalfa leaves, used to line bee brood cells, seemed capable of causing such mortality. Food masses of bee nests from non-alfalfa areas were injected with extracts of leaves from alfalfa plants selected for high or low saponin content. Mortality after injection with these extracts averaged 56.2 and 37.8%, respectively, and that for controls and uninjected cells averaged 29.0 and 5.9%, respectively. This relationship was consistent for 6 different extracts. Purified alfalfa saponins produced bee mortality directly related to saponin concentration. Suggestions to improve bee survival for alfalfa seed production include: selecting low saponin alfalfa lines, increasing bee populations on clovers, and providing alternative leaf forage near alfalfa seed fields.