A revision of the bees of the genus Andrena of the Western Hemisphere: Part XIV—Subgenus Onagrandrena

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

Investigating temporal patterns of a native bee community in a remnant North American bunchgrass prairie using blue vane traps

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.This is the publisher’s final pdf. The published article is copyrighted by the University of Wisconsin Digital Collections Center and can be found at: http://www.insectscience.org/.Keywords: Grasslands, Native bees, Bee monitoring, Community compositionKeywords: Grasslands, Native bees, Bee monitoring, Community compositio

Short-term responses of native bees to livestock and implications for managing ecosystem services in grasslands

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

Delivery of crop pollination services is an insufficient argument for wild pollinator conservation

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

A revision of the bees of the genus Andrena of the Western Hemisphere. Part XV???Subgenus Hesperandrena.

This work reports on a study of 1,200 specimens segregated into 9 species, 4 of which are new to science. One name is relegated to synonymy. The relationships within the subgenus and with other subgenera of Andrena are briefly discussed. The subgenus Hesperandrena was recognized and described by Timberlake in Lanham 1949 (p. 208) to include two previously described species, Andrena escondida Cockerell and Andrena baeriae Timberlake. These two species have in common a propodeum which, Timberlake described as having the dorsal surface, ???... broad, gently curved and inclined from base to apex, without definite truncation, the lateral margins distinctly carinate and convexly arcuate.??? This is the main character separating this subgenus (Fig. 4) from other subgenera of Andrena except that in the males of Hesperandrena the lateral margins of the propodeum are not carinate. Other characters are given in the description of the subgenus below. The species of this subgenus are very similar to one another and difficult to tell apart. The species are known only from California and Baja California. The reader is referred to earlier sections of this revision (LaBerge 1967, 1969, 1971, 1973, 1977, 1980, 1986, 1987, 1989; LaBerge and Bouseman 1970, 1987; LaBerge and Ribble 1972, 1975; Bouseman and LaBerge 1979; Thorp 1969; Donovan 1977) for details of morphology and a more complete bibliography on the genus Andrena. No new terms have been introduced and the bibliography presented here includes only references cited. Published locality and floral records are included in the sections at the end of each species account.published or submitted for publicationis peer reviewe

A List of Bees of Santa Cruz Island, CA

An unpublished checklist of bees created by Dr. Robbin Thorp of Santa Cruz island in 2007.&nbsp