Sujaya Rao

Unscented Color Traps for Non-Apis Bees (Hymenoptera: Apiformes)

Abstract Asian ladybug (semitransparent blue) and Japanese beetle (semitransparent yellow) insect traps (Springstar™) were tested for their utility in studies on bee diversity. The unscented traps were placed at four diverse ecological sites in Oregon in 2004 for approximately 48 hr and catches identified. Trap vanes were highly UV-A and UV-B reflective. The bee catch was diverse with a total of 369 bees, in 17 genera in five families. Bee captures were consistent with bee fauna at each site during the test periods. The semitransparent blue yielded an average of 17.3 bees/trap/day and the yellow 5.75 bees/trap/day. Bombus spp. made up 62.1% of all the bees captured, followed by the halictines (23.8%). It was surprising that Apis was virtually absent from all traps in all zones even though they were abundant in the immediate proximity of each trap. The current study is the first one in which colored traps captured sizeable numbers of bees: 1) in the absence of a pheromone or other attractant; 2) over a short time period of time (48 hr); and, 3) in a selective manner. These studies suggest that a modified SpringStar™ semitransparent blue trap may be a valuable tool in future studies on bee diversity, distribution, seasonal abundance, and bee foraging behavior.

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 to the nest. Very few Apis mellifera (L.) were taken in the traps, whereas they dominated in sweeping and vacuuming samples. These studies suggest that the blue vane traps can serve as an effective sampling tool for bee diversity studies in proximity to stands of intense floral competition.

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

Abstract 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.

The interaction of a Botanophila fly species with an exotic Epichloë fungus in a cultivated grass: fungivore or mutualist?

Epichloë spp. (Ascomycetes: Clavicipitaceae) are endophytic fungii of Pooid grasses that cause choke disease, the suppression of seed production. They also host Botanophila spp. (Diptera: Anthomyiidae), the larvae of which feed on the fungus. Studies on Epichloë elymi on wild grasses indicate that the flies transfer spermatia between Epichloë mating types, thereby affecting cross‐fertilization, suggesting that the fungus–fly interaction reflects obligatory mutualism. Epichloë typhina, inadvertently introduced into western USA, was first detected in cultivated Dactylis glomerata L. fields in 1996. It spread rapidly, raising concerns about impacts on seed production. The present study was conducted to address questions pertaining to the occurrence and nature of the fungus–fly interaction in the new habitat of E. typhina. The first report of an endemic Botanophila species associated with E. typhina in Oregon is presented here. Surveys of D. glomerata fields indicated no correlation between fly abundance and fungal fertilization. In one field, no fly eggs or larvae were detected, but fertilized stromata were universally present. The fly was established in the remaining 12 fields surveyed, but while the number of stromata with fly larvae ranged from 6 to 98%, stromata development was uniform. Up to 10 larvae were present on a stroma, and these consumed >90% of the perithecia. Comparisons of pupal weights indicated that the fungal resource was not limiting, even at high larval densities. An exclusion study in a D. glomerata field also indicated that E. typhina fertilization occurred without the fly. In Oregon, the fly clearly benefits from the association with the fungus, but there is no evidence of benefit to the fungus. Thus if obligatory mutualism in the fungus–fly relationship described from the midwestern USA is the norm, our studies suggest a shift in the interaction to one of simple foraging on the fungus by fly larvae.

Identification of Larvae of Exotic Tipula paludosa (Diptera: Tipulidae) and T. oleracea in North America Using Mitochondrial cytB Sequences

Abstract Two exotic crane fly species, Tipula (Tipula) paludosa Meigen (Diptera: Tipulidae) and Tipula (Tipula) oleracea L. have spread considerably in North America beyond original areas of detection in eastern and western Canada. These species are endemic in Europe, and pests in pastures and cereals. The two species differ in life cycles and periods when they feed, warranting species-specific control. Identification presents a challenge because the larvae are not easily distinguishable from each other, and resemble native nonpestiferous species present in sympatry. We collected crane flies from urban landscapes and agricultural fields in Oregon in the western United States. Using polymerase chain reaction (PCR), we sequenced a portion of the mitochondrial cytB gene in 55 individuals (eight adults and 47 larvae) from 29 sites. We observed 7% divergence between exotic and native species. Phylogenetic analysis, using Nephrotoma ferruginea F. as an outgroup, resolved four well-supported monophyletic groups: the exotics, T. (Tipula) oleracea and T. (Tipula) paludosa, and two natives, Tipula (Serratipula) tristis Doane and Tipula (Triplicitipula) sp. Nucleotide divergence between T. oleracea and T. paludosa was P = 0.071, whereas within species divergence was very low (P = 0.0018 and P = 0.0022, respectively). The study indicated that mitochondrial cytB sequences provided an accurate, rapid, and economic technique for separation of T. oleracea and T. paludosa from each other and from native species, and insights on their habitats. The technique will facilitate early pest management decisions, and studies on host plants and geographic distribution, as the two exotic species extend their ranges across North America.

Bumble Bee (Hymenoptera: Apidae) Foraging Distance and Colony Density Associated With a Late-Season Mass Flowering Crop

ABSTRACT Foraging behaviors of bumble bee workers have been examined in natural habitats, whereas agricultural landscapes, which can provide insights on flight distances to fragmented patches of bloom, have received limited attention. In particular, information on worker flight distances to crops blooming several months after nests have been established is invaluable. Here, we examined foraging patterns of Bombus vosnesenskii Radoszkowski in late-season blooming clover in the agriculturaldominated Willamette Valley in Oregon. Workers from 10 fields collected over 2 yr were assigned to full sibling families (colonies) by using eight microsatellite loci. With estimation of numbers of unseen species, we inferred the presence of 189 colonies from 433 bees genotyped in year 1, and 144 from 296 genotyped the next year. Worker foraging distance was estimated to be at least 11.6 km, half the distance between the most remote fields visited by the same colonies. Numbers of nests contributing workers to each field ranged from 15 to 163. Overall, 165 (50%) colonies foraged in two or more fields, and thus used common resources within the landscape. Estimates of average nest densities in the landscape each year ranged from 0.76/km2 to 22.16/km2, and highlighted the influences of various study parameters incorporated into the calculation including sample size, distances between sites, and analytical tools used to estimate unsampled individuals. Based on the results, bumble bees can fly long distances, and this could facilitate their survival in fragmented agricultural landscapes. This has important implications for the scale of habitat management in bumble bee conservation programs.

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.

The Botanophila–Epichloë association in cultivated Festuca in Oregon: evidence of simple fungivory

We investigated the Botanophila (Diptera: Anthomyiidae)–Epichloë (Ascomycetes: Clavicipitaceae) interaction in cultivated Festuca spp. (fine fescue) in Oregon in western USA. Epichloë spp. are endophytic fungi of grasses in the subfamily Pooideae. They develop a felt‐like stroma on the surface of grass culms and a dense mycelium within the culms that typically prevents seed head emergence. As a result, seed yields are suppressed, and hence the disease is known as choke. Studies of Epichloë spp. on wild grasses indicate that the fly–fungus interaction is an obligatory mutualism. During oviposition, Botanophila transfers Epichloë spermatia between stromata of opposite mating types, and the perithecia that develop after fungal fertilization serve as food for Botanophila larvae. In the current study, we surveyed 19 cultivated fields of Festuca spp. in Oregon, and observed choke caused by Epichloë festucae Leuchtmann, Schardl and Siegl in 10 of these. However, perithecia were observed in only four fields, and on only 1.0–2.6% of stromata. Perithecial development was also low, and rarely covered 50% of the stroma surface. Despite the absence or low frequency of fertilized stromata, Botanophila lobata Collin larvae were present in all choke‐infested fields. Infestation levels ranged from 2.5 to 70.7%, based on an examination of 175–200 stromata from each field. Only eight (= 2%) of the 450 stromata with B. lobata had perithecia, and the greater majority of B. lobata larvae completed development and exited from unfertilized stromata. This is the first report of the B. lobata–E. festucae association in the USA, and of B. lobata larvae developing successfully on unfertilized Epichloë stromata. The average pupal weight (0.0032 g) did not differ significantly from pupae (0.0030 g) originating from larvae that had developed on fertilized stromata of E. typhina on Dactylis glomerata in a neighboring field. This result indicates that in cultivated fine fescue fields in Oregon, B. lobata forages on E. festucae, but fly development is not dependent on the fertilized stromata of Epichloë.

Bombus (Bombus) occidentalis (Hymenoptera: Apiformes): In decline or recovery

Bombus (Bombus) occidentalis Greene, 1858 is readily distinguished from other North American (excluding Alaskan) forms of the subgenus Bombus by its distinctive white pile on the apex of metasomal tergum 4 and on terga 5 and 6 (Stephen 1957, Thorp et al. 1983). It has been treated as a polymorphic species (Franklin 1913, Stephen 1957, Thorp et al. 1983, Scholl et al. 1990) and as a synonym of B. terricola Kirby (Milliron 1971, Poole 1996). As its status has yet to be resolved, we are treating forms with black pile on the metasoma terga 1–3 as B. o. occidentalis (5 typical form) and those with yellow pile on tergum 3 as B. o. nigroscutatus Franklin, 1913. Bombus o. occidentalis was one of the most common Bombus species on the west coast and in the coastal Valleys from the Bay Area of CA to the Alaska Panhandle until the mid 1990’s. It is now thought to be near extinction (Thorp 2003, Thorp & Sheppard 2005, NAS 2006). We have not seen it in the Willamette Valley since the spring of 1997, although a queen was sighted on a blueberry plant at Umpqua, Oregon in 2002 (R. Thorp, personal communication). Another queen, collected on 9 July 2005 in Victoria, British Columbia, Canada, was posted at http:// bugguide.net/node/view/23813. In the summer of 2006, during a study on native bee diversity and abundance in the Willamette Valley of western Oregon, we collected three workers of B. o. occidentalis. The specimens were collected in unscented translucent blue vane traps described in Stephen & Rao (2005), that were set up in clover seed production fields. The specimens will be deposited in the Oregon State University Arthropod Collection. Collection data are:

The Status of the ‘Red-Listed’ Bombus occidentalis (Hymenoptera: Apiformes) in Northeastern Oregon

Abstract The western bumble bee, Bombus occidentalis, is included on the red list of bees by The Xerces Society. It was once a common bumble bee west of the Cascades but in the late 1990s it experienced a dramatic decline along coastal regions. The cause was speculated to be due to the introduction of pathogens from captive-bred bumble bees used for pollination of greenhouse crops. In extensive surveys conducted in western and southern Oregon, 10 individuals have been recorded since 2000. In this note, we report the collection of 49 individual B. occidentalis over two years in the Zumwalt Prairie Preserve of northeastern Oregon. This finding shows that B. occidentalis persists in northeastern regions of the Pacific Northwest, either because of geographic isolation from or potential resistance to the pathogens that decimated populations in the western part of the region. Further research is needed to determine its occurrence in other regions of its historical range to assess the extent of its decline. In addition, conservation efforts are critical for protection of this species in both agricultural ecosystems and in native habitats.