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.

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

“…Although the Zumwalt Prairie has been used as summer pasture for horse, sheep, and cattle for over 100 years, the majority of the area remains dominated by native species including Idaho fescue (Festuca idahoensis), prairie Junegrass (Koeleria macrantha), and bluebunch wheatgrass (Pseudoroegneria spicata) (Kennedy et al 2009, Bartuszevige et al 2012. In addition, a rich forb community (.112 species of forbs) is associated with a diverse bee community (.200 species in 27 genera), with the most common genera being sweat bees of the genus Lasioglossum (Halictidae) and bumble bees (Bombus: Apidae) (Kimoto et al 2012). …”

“…No liquids or other killing agents were used in traps. We used blue vane traps because they provided a number of advantages in sampling expansive grassland habitats over other commonly used methods, such as hand-netting and pan-trapping (detailed in Kimoto et al 2012). Advantages include the fact that relatively few traps are needed to collect large numbers of bees, traps are easy to work with in field conditions and are highly selective for bees, and their effectiveness is not affected by the experience and capabilities of the sampler (Westphal et al 2008).…”

“…This is true despite the fact that livestock grazing is the most common use of grasslands world-wide (White et al 2000). Many of these grasslands, including those in western North America, support a diverse and abundant bee fauna (Kimoto et al 2012).…”

The native bee fauna of the Palouse Prairie (Hymenoptera: Apoidea)

“…Pan traps have been extensively used in standardized bee sampling regimes, but are known to have bias in bee capture, recovering Halictinae and Perdita Smith at greater rates than the genera Anthidium Fabricius, Colletes Latreille, and Epeolus Latreille, as compared with netting in the same locations (Wilson et al, 2008). Blue vane traps were used so we could better compare results with the only other systematic bee collection effort in Pacific Northwest bunchgrass prairie, which was performed using only blue vane traps (Kimoto et al, 2012). Blue vane traps filled with soapy water (Springstar Inc., Woodinville, WA) were hung about one meter off the ground on a bamboo tripod at the randomly determined sampling location.…”

“…There are four instances where Bombus community data can be compared to the Palouse: 1) A 2003 survey of Bombus was performed in the Palouse Prairie, reflecting recent community composition (Hatten et al, 2013); and 2) a GBIF-derived dataset with 1675 records of Bombus occurrence when limited to pre-2000 records (1805-1999) within the Palouse, reflecting historical community composition [the preponderance of post-1999 records in the GBIF database were from the Hatten et al (2013) study]; 3) a recent survey of native bees on the Zumwalt prairie (Kimoto et al, 2012); and 4) Bombus community data extracted from a bee study of the nearby Okanogan National Forest (Wilson et al, 2010). Bray-Curtis dissimilarity was calculated using the vegan package in R (Oksanen et al, 2015;R Core Development Team, 2015), among these four datasets to evaluate: 1) the similarity of the Palouse Bombus community through time, and 2) the similarity of the contemporary Palouse Bombus community to nearby habitats.…”