Native Bee Species Research Articles

Rangeland Management for Pollinators

Pollinator conservation and rangelands don’t seem like obvious bedfellows. In this era of sustainability, the connection between pollinator conservation and row crops or pollinator conservation and orchards is obvious. But pollinator conservation and rangelands? The reality is that pollinators are a key component of a healthy rangeland ecosystem. As Kevan stated, pollination is “central to all human beings, livestock, and wildlife.”1 Pollinators are essential for rangeland food production, help with nutrient cycling, and are prey for many birds. In essence, they hold a central position in wildlife food webs. For example, many migratory songbirds require a diet of berries, fruits, and seeds from insect-pollinated plants and pollinator larvae are an important component of the diet of many young birds. Belfrage et al. demonstrated that butterfl y diversity was a good predictor of bird abundance and diversity, apparently due to a shared requirement for a complex plant community.2 Pollinators perform such a range of ecological services in natural ecosystems that they are clearly a keystone group in nearly all terrestrial ecosystems and are necessary for plant reproduction and in forming the basis of an energy-rich food web.3 The relationship between pollinators and rangeland goes both ways. Pollinators are important for rangelands but rangelands are important for pollinators because they can provide habitat. Pollinators in North America include hummingbirds and bats, but insects—mainly bees, butterfl ies, moths, wasps, fl ies, and beetles—make up the vast majority of pollinators. Of these, bees are considered the most important pollinators in temperate North America. There are approximately 4,000 species of native bees in North America, many of which will thrive in the varied conditions offered by rangelands. Shrubland and scrub habitat, in particular, can be very valuable habitat. Surveys of pollinators in different California plant communities show that the chaparral community has the largest diversity of bees per unit area of any ecosystem type. Bee habitat requires two basic components: fl owers on which to forage and nest sites. Many pollinators are adapted to forage on particular plants, so a diverse community of pollinators requires a diverse array of fl owers. This can be easily provided by native grassland comprising a variety of grasses and forbs. Most native bees are solitary-nesting. Around 70% of bee species nest in the ground, excavating shallow tunnels in patches of bare soil, with most of the remaining 30% nesting in cavities in old trees or plant stems. Bumble bees require a small cavity such as an abandoned rodent hole. Ground-nesting bees (both solitary bees and bumble bees) are likely the most important pollinators in grasslands, but fl ies, beetles, and butterfl ies will also be prevalent. Rangeland pollinators have benefi ts that go beyond the boundaries of the range. The role that adjacent natural habitat (including grassland, shrubland, and other rangeland types) plays in providing crop pollination services is increasingly well understood: The value of crop pollination by native, wild bees in the United States is estimated at $3 billion. Proximity to natural or seminatural nonagricultural land is often an important predictor of pollinator diversity in cropland. There is evidence of declines in both managed and wild pollinators. Causes of declines are diffi cult to pinpoint, but loss of habitat due to increasing urbanization, expansion of intensive agriculture, invasive plant species, and the widespread use of pesticides all negatively impact pollinator populations, as do disease and parasites affecting the pollinators themselves. Protection of habitat is one way in which rangelands can be of great signifi cance in protecting and conserving pollinators. Natural habitat is integral to maintaining a long-term population of native pollinators in agricultural landscapes. However, it is important that management of rangelands and other nonarable lands takes into account native pollinators.

Native Bees, Honeybees, and Pollination in Oregon Cranberries

Cultivated cranberry (Vaccinium macrocarpon Aiton) relies on insect pollination for berry production. Honeybees (Apis mellifera L.) have historically provided this service, but their recent decline has underscored the need for additional pollinators. The objective of this study was to determine the richness and abundance of native bees in the cranberry-growing area of southern coastal Oregon and compare foraging behaviors of honeybees and native bees. In a 2-year study, we collected over 27 native bee species in traps set out during and after bloom (mid-May to mid-June). During 67 2-min observations, honeybees (68.1%) and three species of bumble bees (Bombus spp.; 31.6%) comprised 99.7% of foragers. The dominant bumble bee was Bombus vosnesenskii Radoszkowski (56.0%). Multivariate regression of temperature and wind speed data indicated that both were significantly predictive of honeybee and bumble bee foragers (P < 0.001). The interquartile range for foraging was 18.3 to 22.2 °C for bumble bees and 21.1 to 26.7 °C for honeybees. Over 75% of honeybees were seen foraging above the average observed temperature (19.5 °C). Bumble bee pollen loads had a greater dry mass (6.8 ± 12.9 mg) than those of honeybees (2.0 ± 3.6 mg; P < 0.001), and the latter were observed collecting nectar but no pollen more often (during 37.2% of visits) than bumble bees (11.3% of visits). Based on our results, bumble bees in general, and B. vosnesenskii in particular, may be providing significant pollination services for Oregon cranberry farms. However, to maintain current native bumble bee populations, conservation efforts are recommended.

The effect of colour variation in predators on the behaviour of pollinators: Australian crab spiders and native bees

Australian crab spiders exploit the plant-pollinator mutualism by reflecting UV light that attracts pollinators to the flowers where they sit. However, spider UV reflection seems to vary broadly within and between individuals and species, and we are still lacking any comparative studies of prey and/or predator behaviour towards spider colour variation. 2. Here we looked at the natural variation in the coloration of two species of Australian crab spiders, Thomisus spectabilis and Diaea evanida, collected from the field. Furthermore, we examined how two species of native bees responded to variation in colour contrast generated by spiders sitting in flowers compared with vacant flowers. We used data from a bee choice experiment with D. evanida spiders and Trigona carbonaria bees and also published data on T. spectabilis spiders and Austroplebeia australis bees. 3. In the field both spider species were always achromatically (from a distance) undetectable but chromatically (at closer range) detectable for bees. Experimentally, we showed species-specific differences in bee behaviour towards particular spider colour variation: T. carbonaria bees did not show any preference for any colour contrasts generated by D. evanida spiders but A. australis bees were more likely to reject flowers with more contrasting T. spectabilis spiders. 4. Our study suggests that some of the spider colour variation that we encounter in the field may be partly explained by the spider's ability to adjust the reflectance properties of its colour relative to the behaviour of the species of prey available.

Reproductive Biology, Hybridization, and Flower Visitors of RareSclerocactusTaxa in Utah's Uintah Basin

We studied the mating system and flower visitors of 2 threatened species of Sclerocactus (Cactaceae) in the Uintah Basin of eastern Utah—an area undergoing rapid energy development. We found that both S. wetlandicus and S. brevispinus are predominantly outcrossed and are essentially self-incompatible. A third presumptive taxon (undescribed; here called S. wetlandicus-var1) is fully self-compatible but cannot produce seeds unless the flowers are visited by pollinators. We found tentative evidence for pollinator limitation of fruit set in S. brevispinus but not in the other taxa. Pollinators are largely species of native ground-nesting bees in the subfamily Halictinae. These bees are indiscriminate collectors of pollen and nectar from Sclerocactus flowers and other plant species. The well-being of Sclerocactus populations requires that land managers ensure the preservation of halictid bee habitat, which includes both nesting sites and a diversity of floral resources. These bees are also undoubtedly the pollen vectors responsible for the production of hybrids in areas where S. wetlandicus and S. brevispinus meet. We experimentally confirmed that reciprocal crosses between S. wetlandicus and S. brevispinus are indistinguishable from each other or from pure crosses in fruits/flower, seeds/fruit and seed weights. We suggest that hybridization preceded energy development, that it attests to the ongoing process of evolution in the Sclerocactus group, and that it should not be suppressed by anthropogenic activity.

Differential antimicrobial activity in response to the entomopathogenic fungus Cordyceps in six Australian bee species

Microbial pathogens were important in the evolution of insect societies and remain a major cause of colony death. The differential effects are reported of antimicrobial compounds extracted from six species of Australian native bees on the spores and hyphae of the entomopathogenic fungus Cordyceps bassiana. The bee species were: Amegilla bombiformis, A. asserta, Exoneura robusta, E. nigrescens, Exoneurella tridentata and Trigona carbonaria. The fungus was isolated from E. robusta and it was this species that showed the greatest activity against both Cordyceps spore germination and hyphal growth. One explanation is that anti-Cordyceps activity may have been under greatest selection in this bee species, but its congener, E. nigrescens, showed only slightly weaker activity against the pathogen. In contrast, A. bombiformis, A. asserta, E. tridentata and T. carbonaria showed considerable variation in anti-Cordyceps activity. Nevertheless, there was a trend of greater activity against Cordyceps spore germination than hyphal growth. On the basis of this result, a mechanism whereby fungal pathogens may have been important drivers of social evolution is suggested.

Reproduction of Echinacea angustifolia in fragmented prairie is pollen‐limited but not pollinator‐limited

Pollen limitation of plant reproduction occurs in many plant species, particularly those in fragmented habitat; however, causes of pollen limitation are often unknown. We investigated the relationship between pollen limitation and pollinator visitation in the purple coneflower, Echinacea angustifolia (Asteraceae), which grows in the extremely fragmented tall grass prairie of North America. Previous investigations showed that pollen limitation of E. angustifolia increases with plant isolation and decreases with population size. We observed insect visitation to E. angustifolia over two flowering seasons and estimated pollen limitation of observed plants, using seed set as a proxy measure in 2004 and persistence of receptive style rows in 2005. We analyzed spatial patterns of bee visitation and pollination at two spatial scales: individual isolation, as measured by the distance to their kth nearest flowering neighbors (k = 1 - 15), and population size. Our results indicate that E. angustifolia is pollinated by over 26 species of native bees, with 70-75% of visits by halictid bees. Surprisingly, in both years, bee visitation increased with isolation of individual plants and did not vary significantly with population size. As expected, plant isolation increased pollen limitation and lowered seed set. There was no effect of population size on seed set in 2004, and pollen limitation decreased nonsignificantly with population size in 2005. We conclude that pollen receipt limits reproduction in E. angustifolia, but pollinator visitation does not. Remarkably, isolated plants simultaneously have increased rates of pollinator visitation by pollinators and decreased reproduction. We discuss alternative explanations of pollen limitation that are consistent with this apparent discrepancy, including a decline in the availability of compatible conspecific pollen with increased plant isolation.

Relocation and establishment of nesting populations of the native bee Leioproctus huakiwi Donovan (Hymenoptera: Colletidae).

Environmental changes in New Zealand over the last 200 years such as the intensifi cation of agriculture have nearly eliminated some species of native bees from parts of their historic ranges. Consequently, the reproductive success of native plants reliant on native bees for pollination may be adversely impacted, thereby altering native ecosystems. The potential pollination rate of some introduced crops might also be reduced. Overwintering prepupae of the ground-nesting colletid bee Leioproctus huakiwi Donovan, 2007, were relocated in nests in soil and in artifi cial cells to new nest sites, where they established new populations which expanded by about 8-25 times over three years (and for the two sites together by 12.75 times), showing that large populations can develop rapidly. The two transference methods should be applicable to other species of colletids, indicating that relocation of these bees to new areas for both conservation and economic values is readily achievable.

Reproductive and Pollination Biology of the Endemic Hawaiian Cotton, Gossypium tomentosum (Malvaceae)

Abstract: Gossypium tomentosum is a cotton species endemic to the Hawaiian Islands. We studied several aspects of its reproductive biology, including potential pollinators, floral biology, and diurnal and seasonal flowering phenology. Flower visitors were observed in G. tomentosum populations on O'ahu, Kaho'olawe, and Maui. Primary visitors were introduced species, honeybees and carpenter bees, both of which were pollinating the flowers. No native bee species were seen visiting flowers. In examining floral biology we found that in some cases 10% of flowers had styles that were as short as the anthers or were recurved toward the anthers. In the greenhouse, in the absence of pollinators, these flowers were the only ones that set fruit. Flowering of G. tomentosum commences in January and February, following the rainy season, peaks in May, and may continue into August and September. In one year, after higher than average precipitation during the rainy season, there was a greater abundance of flowering, and fl...

Impacts of alien bees on native plant-pollinator relationships: A review with special emphasis on plant reproduction

Alien pollinators can disrupt mutualistic plant-animal interactions. Here we review studies on alien bee pollinators, demonstrating the ways in which invasive honeybees and bumblebees affect native plant seed production. Impacts of alien pollinators vary among pollination systems and among components of pollination success (visitation frequency, pollen transfer per visit, and pollen limitation). Reproduction of native bird-pollinated plants is little impacted by alien honeybees, because birds can pollinate even when honeybees visit target flowers. In bee-pollinated native plants, alien honeybee impacts on reproduction may be pervasive, but are not clearly defined in many cases; this lack of clarity arises because very few control sites without invasive bees are available, making comparative evaluation impossible. In bumblebee-pollinated plants, alien bumblebee effects are strong because native and invasive bee species are closely related congeners (of the genus Bombus) with similar pollinator mechanisms; alien bumblebees compete strongly with natives or replace them. In general, morphological, ecological, and behavioral similarities between native and alien pollinators are important for predicting their competitive interaction intensities and their effects on plant reproduction. The impacts of alien bees include (1) decreased pollen transfer per visit because of the loose morphological correspondence between flowers and alien bees, (2) increased competition for floral resources and exclusion of native pollinators because native and alien bees have similar ecological requirements, (3) changes in native pollinator visitation frequency and pollination efficiency caused by particular alien pollinator behavioral traits (such as stealing nectar or collecting previously-deposited pollen from stigmas). For a quantitative evaluation of invasion impacts, it is important to determine whether native plants suffer pollen limitation. To demonstrate pollen limitation, comparative studies with controls (that lack alien pollinators) are required. This approach is essential for discerning possible mechanisms responsible for observed patterns.

Competition between honeybees (<i>Apis mellifera</i>) and native solitary bees in the Mediterranean region of Israel—Implications for conservation

The hypothesis that honeybees (Apis mellifera) compete for floral resources with native bees was studied mainly in areas outside the original range of the honeybees, i.e., where they are introduced. We studied the effect of honeybees on the foraging behavior of native solitary bees in Israel, within the natural distribution range of the honeybee, by manipulating the presence and absence of beehives in the study sites: Ramat Hanadiv Park and Carmel National Park. We examined the possible degree of competition between honeybees and native solitary bees by observing their foraging on focal nectariferous plants. Temporal introduction of hives increased the visitation frequencies of honeybees to our focal plants and decreased the overall average visitation frequencies of native solitary bees. However, the effect of honeybees varied among native bee species, focal plants, and years. In some cases, honeybees had a negative effect on visitation rates of the other bees, while in other cases we did not find such an...

Comparisons of breeding systems between two sympatric species, Nastanthus spathulatus (Calyceraceae) and Rhodophiala rhodolirion (Amaryllidaceae), in the high Andes of central Chile

AbstractAlpine vegetation occurs over a wide range of ecological conditions. Thus, the breeding systems of alpine plants are likely to be diverse and vary from one geographical area to another. The reproductive characteristics of Nastanthus spathulatus (Calyceraceae) and Rhodophiala rhodolirion (Amaryllidaceae), species with contrasting floral morphology, were studied in the high Andes of Chile, which has a Mediterranean‐type climate. Natural and supplemental open pollination, and cross pollination and self‐pollination trials were carried out in the field. Flower visitors were quantified by field and video observations. Both species had high outcrossing properties, and Nastanthus was strongly self‐incompatible. Rhodophiala could form some seed by self‐pollination, but fruit and seed sets were much lower after self‐pollination compared with outcrossing. The phenology and flower/inflorescence forms of these species supported the view that alpine flowers are comparatively long lived and that the floral display contributes to a large proportion of the plant biomass. Rhodophiala was well attended by a native bee species (Megachile sauleyi) that was appropriately sized for efficient pollination. Although no flower visitors were observed on Nastanthus and wind pollination was discarded experimentally, a high proportion of the flowers produced seeds under natural pollination. Therefore, the seed set was not severely pollen limited in these species. Including previously published information, breeding systems are now known for 12 species on this Mediterranean alpine site and current knowledge suggests an emphasis on outcrossing breeding systems.

Wild Bees (Hymenoptera: Apoidea: Anthophila) of the Michigan Highbush Blueberry Agroecosystem

AbstractHighbush blueberry (Vaccinium corymbosum L.) is a native North American crop dependent upon pollen movement by bees for high fruit set and large berries. Commercial blueberry farms use honey bees (Apis mellifera L.) to provide pollination services, but there is concern regarding their long-term sustainability as crop pollinators. We conducted a 3-yr study at 15 farms to identify the bee community associated with the blueberry agroecosystem in Michigan to improve our understanding of this community and to better target conservation practices. Pan trapping and direct observation were used to determine the relative abundance and diversity of wild bees before, during, and after bloom. We found at least 166 species, representing 30 genera and five families, 112 of which were active during bloom. Most bees captured were solitary, soil-nesting bees. Most species were from subfamily Halictinae (family Halictidae) and genus Andrena (family Andrenidae). Andrena Carolina Viereck, a specialist on Ericaceae, was the most abundant native bee species collected during blueberry bloom. Several native Osmia species that were present in low abundance during bloom are potential targets for management. Honey bees were more often captured in white than in yellow traps, regardless of trap position in the field. Wild bees were more often captured in field perimeters than interiors, but they did not respond differentially to trap color. We report seven new state records for Michigan, including significant range extensions, and three new floral record associations. Implications for the conservation of native bees in this agricultural system are discussed.

Bee communities (Hymenoptera: Anthophila) of the “Cerrado” ecosystem in São Paulo State, Brazil

Five surveys of the bee communities in four "Cerrado" ecosystem reserves in São Paulo State were compared for species richness and similarity. These areas are fragment vegetation reser-ves located in the Cerrado Corumbataí Reserve (Corumbataí), Jataí Ecological Park (Luiz Antônio), Cajuru (Cajuru), and Vassununga State Park - "Gleba de Cerrado de Pé-de-Gigante" (Santa Rita do Passa Quatro). The methodology consisted of capturing bees foraging on flowers along transects, though with small differences between surveys. These "cerrado" areas have a large number of species of native bees, which are important pollinators in several Brazilian ecosystems. The community of bees varied among these different fragments. Based on 500 individuals (standardized by rarefaction), Cajuru, Corumbataí 1 and Corumbataí 2 were the areas with highest species richness, and Jataí and Pé-de-Gigante had the lowest species richness in the bee communities. The bee faunas of Corumbataí 2 and Pé-de-Gigante had the highest similarity, forming a group with the bee fauna of Cajuru. The bee faunas of Corumbataí 1 and Jataí were isolated from this group. We found that the bee species richness and similarity found in these "cerrado" areas cannot be explained by general factors such as the size of the fragment, the species richness of plants and the distance between the areas. Therefore, we suppose that local factors that differ among areas, such as interactions between populations, and competition and interference from surrounding areas influence and determine bee species richness and similarity in these reserves.

English

A variety of crops are grown in New York City community gardens. Although the production of many crops benefits from pollination by bees, little is known about bee abundance in urban community gardens or which crops are specifically dependent on bee pollination. In 2005, we compiled a list of crop plants grown within 19 community gardens in New York City and classified these plants according to their dependence on bee pollination. In addition, using mark-recapture methods, we estimated the abundance of a potentially important pollinator within New York City urban gardens, the common eastern bumble bee (Bombus impatiens). This species is currently recognized as a valuable commercial pollinator of greenhouse crops. However, wild populations of B. impatiens are abundant throughout its range, including in New York City community gardens, where it is the most abundant native bee species present and where it has been observed visiting a variety of crop flowers. We conservatively counted 25 species of crop plants in 19 surveyed gardens. The literature suggests that 92% of these crops are dependent, to some degree, on bee pollination in order to set fruit or seed. Bombus impatiens workers were observed visiting flowers of 78% of these pollination-dependent crops. Estimates of the number of B. impatiens workers visiting individual gardens during the study period ranged from 3 to 15 bees per 100 m of total garden area and 6 to 29 bees per 100 m of garden floral area. Of 229 B. impatiens workers marked, all recaptured individuals (45%) were found in gardens where they were initially marked. These results indicate an abundance of B. impatiens workers within New York City community gardens and suggest that, at least for certain time periods, many individual workers forage within single gardens. Both findings suggest that B. impatiens may be an especially important pollinator of several common crops grown within community gardens and other urban green spaces that are used for agricultural production. Studies of other pollinating insect species in urban habitats as well as the relationship between pollen movement and seed or fruit set will complement the findings of this study.

ALIEN BUMBLE BEE AFFECTS NATIVE PLANT REPRODUCTION THROUGH INTERACTIONS WITH NATIVE BUMBLE BEES.

The invasive alien bumble bee Bombus terrestris may hinder the reproduction of native plants that have established specialized pollination systems with native bumble bees. To test this hypothesis, we examined the visitation frequency and behavior of native and alien bumble bee species and resultant seed production in Corydalis ambigua, a native plant in Hokkaido, Japan. This species is self-incompatible: the flower has a spur and requires visitation by bumble bees for effective seed production. We compared visitation frequency as well as fruit and seed set after cross- and open pollination at five sites of C. ambigua. Four of these sites occurred near a residential district and included naturalized populations of B. terrestris, and the fifth site was located in a forested habitat with no B. terrestris. The native species B. ardens and B. hypocrita and the alien B. terrestris frequently visited C. ambigua. Bombus ardens legitimately consumed nectar, whereas B. hypocrita and B. terrestris rob nectar by perforating spurs. The legitimate pollinator B. ardens produced fruits and seeds more efficiently than the nectar robbers. At three sites, the proportion of robbed flowers per inflorescence gradually increased through the flowering period, which may be caused by the intrusion of alien B. terrestris into the native plant-pollinator interactions. At these sites, C. ambigua suffered from pollen limitation, as seed production from open pollination was lower than from cross-pollination, despite the fact that the total abundance of three bumble bees was higher than in the other two sites. Legitimate B. ardens visited fewer flowers within inflorescences with more robbed flowers, suggesting that nectar robbing may reduce the frequency of visitations by B. ardens within inflorescences, and resulting in decreased fruit set. Furthermore, reduced seed set implies a reduction in the pollination quality by B. ardens, probably due to decreases in visiting time per flower. Thus, introduction of alien B. terrestris may alter the native plant-pollinator mutualism: C. ambigua could establish a novel pollination relationship with B. terrestris because of its nonzero pollination efficiency, similar to the native robber B. hypocrita.

Pollen and nectar as a reward in the basal epidendroid Psilochilus modestus (Orchidaceae: Triphoreae): A study of floral morphology, reproductive biology and pollination strategy

Psilochilus modestus Barb. Rodr. is a basal epidendroid orchid occurring in both the semi-deciduous and Atlantic rain forests of the state of São Paulo, southeastern Brazil. This species presents a perfect flowering synchrony within populations, since all the mature buds of each plant open simultaneously in the morning hours of the same day. These flowers are available only for 1 day and are pollinated by several species of small solitary and social native bees. These bees exploit both pollen and nectar as a reward. The bees collecting pollen promote a higher fruit set and perform mainly self-pollination while those collecting nectar, which are less numerous, are responsible for an increase in cross-pollinations. P. modestus is self-compatible but pollinator dependent. Natural fruit set (open pollination) is low when compared with the numbers obtained under manual self- and cross-pollination. Low fruit set in natural conditions is related to deficient pollen transfer, and pollinator inefficiency seems to be the main factor. Some factors, such as the small amount of nectar produced, the low number of flowers per inflorescence and their availability for 1 day only added to the perfect flowering synchrony seem to be responsible for the increase of cross-pollinations. The offering of both pollen and nectar as a reward can represent a transitional condition in basal Epidendroideae. Based on floral morphology, reward production and pollinator behavior, the relationship of P. modestus with the basal and most derived groups within Orchidaceae is discussed.

Sampling Native Bees in Proximity to a Highly Competitive Food Resource (Hymenoptera: Apiformes)

Abstract The efficacy of sweeping and vacuuming as methods of sampling native bees were compared to those of passive blue and yellow translucent-vane traps located adjacent to a highly attractive forage source, Helianthus spp. (Asteraceae). A total of 35 species of native bees belonging to 12 genera were caught during September, 94% in the passive blue-vane traps, 63% by sweeping, and 54% by vacuuming and yellow-vane traps. Overall, 55.7 % of all the native bees trapped in the study across the four treatments were collected in the blue vane traps. There were almost double the number of species, and over five times more individuals in blue vane traps than in the yellow. Agapostemon virescens (Fabr.) was the predominant species collected across all methods (400 of 1208). The majority of females (> 99%) captured in the blue vane traps lacked pollen suggesting that the bees may have been diverted by the reflected light from the trap during their flight to the floral sources rather than on their return flight ...

Orchard pollination in Capitol Reef National Park, Utah, USA. Honey bees or native bees?

Capitol Reef National Park in central Utah, USA surrounds 22 managed fruit orchards started over a century ago by Mormon pioneers. Honey bees are imported for pollination, although the area in which the Park is embedded has over 700 species of native bees, many of which are potential orchard pollinators. We stud- ied the visitation of native bees to apple, pear, apricot, and sweet cherry over 2 years. Thirty species of bees visited the Xowers but, except for pear Xowers, most were uncommon compared to honey bees. Evidence that honey bees prevented native bees from foraging on orchard crop Xowers was equivocal: generally, honey bee and native bee visitation rates to the Xowers were not negatively correlated, nor were native bee visitation rates positively correlated with distance of orchards from honey bee hives. Conversely, competition was tentatively suggested by much larger numbers of honey bees than natives on the Xowers of apples, apricots and cherry; and by the large increase of native bees on pears, where honey bee numbers were low. At least one-third of the native bee species visiting the Xowers are potential pollinators, including cavity-nesting species such as Osmia lignaria propinqua, currently managed for small orchard pollination in the US, plus several fossorial spe- cies, including one rosaceous Xower specialist (Andrena milwaukiensis). We suggest

Conservation Status of the Endemic Bees of Hawai‘i, Hylaeus (Nesoprosopis) (Hymenoptera: Colletidae)

The 60 species of native Hylaeus bees in the Hawaiian Islands are important pollinators in native ecosystems, but they have been almost completely ignored in conservation studies. The only previous assessment of the conservation status of the individual species was not based on recent collections. Here I report on conservation status of all known species, based on collections made from 1999 to 2002. Species are arranged into six categories according to degree of threat, and species considered to be threatened are discussed individually. Five species have not been collected recently from one or more islands from which they are historically known, seven are restricted to endangered habitat, 10 are considered to be very rare and potentially endangered, and 10 have not been collected recently and could be extinct. With such a high proportion of rare species and the importance of Hylaeus species as pollinators, further work on their ecology is needed.

Electrospray ionization mass spectrometry fingerprinting of propolis of native Brazilian stingless bees

Stingless bees are found in many tropical and subtropical regions of the word. The knowledge of the composition of their propolis as well as the plants that are visited as sources of resins is therefore of prime importance. Here the negative ion mode electrospray ionization mass spectrometry [ESI(-)-MS] fingerprints of propolis from various species of native stingless bees from different regions in Brazil are compared to determine their composition patterns. The correlation among the propolis samples was investigated via chemometric analysis.