DOI: 10.5061/dryad.9kd51c5mc
title: Six years of wild bee monitoring collections data using Blue Vane traps in Southern Pennsylvania, USA

description: Turley NE, Biddinger DJ, Joshi NK, López-Uribe MM. 2022. Six years of wild
 bee monitoring shows changes in biodiversity within and across years and
 declines in abundance. Ecology and Evolution.    Wild
 bees form diverse communities that pollinate plants in both native and
 agricultural ecosystems making them both ecologically and economically
 important. The growing evidence of bee declines has sparked increased
 interest in monitoring bee community and population dynamics using
 standardized methods. Here, we studied the dynamics of bee biodiversity
 within and across years by monitoring wild bees adjacent to four apple
 orchard locations in Southern Pennsylvania, USA. We collected bees using
 passive Blue Vane traps continuously from April to October for six years
 (2014-2019) amassing over 26,000 bees representing 144 species. We
 quantified total abundance, richness, diversity, composition, and
 phylogenetic structure. There were large seasonal changes in all measures
 of biodiversity with month explaining an average of 72% of the variation
 in our models. Changes over time were less dramatic with years explaining
 an average of 44% of the variation in biodiversity metrics. We found
 declines in all measures of biodiversity especially in the last 3 years,
 though additional years of sampling are needed to say if changes over time
 are part of a larger trend. Analyses of population dynamics over time for
 the 40 most abundant species indicate that about one third of species
 showed at least some evidence for declines in abundance. Bee family
 explained variation in species-level seasonal patterns but we found no
 consistent family-level patterns in declines, though bumble bees and sweat
 bees were groups that declined the most. Overall, our results show that
 season-wide standardized sampling across multiple years can reveal nuanced
 patterns in bee biodiversity, phenological patterns of bees, and
 population trends over time of many co-occurring species. These datasets
 could be used to quantify the relative effects that different aspects of
 environmental change have on bee communities and to help identify species
 of conservation concern. 
description: <strong>Study site</strong> Our
 study took place between 2014 and 2019 at the Pennsylvania State Fruit
 Research and Extension Center in Adams County, Pennsylvania, USA
 (39.935226, -77.254530) and nearby apple orchards. This site has an
 average yearly rainfall of 112 cm, average summer temperature ranging from
 16 °C to 28 °C, and average winter temperatures of -5 °C to 5 °C
 (Biddinger et al., 2018). The landscape is hilly with well-drained soils
 and the broader area is approximately 56% broadleaf forest fragments, 25%
 pastureland, 9% developed areas, and 8% commercial orchards (Biddinger et
 al., 2018). All orchards were managed under growers’ choice conventional
 pest management programs that use pesticide classes including insect
 growth regulators, anthranilic diamide, tetramic acid, microbials, and
 neonicotinoid insecticides (Biddinger et al., 2018). We sampled bees at 8
 locations adjacent to 4 different active apple orchards. Sampling
 locations were within 150 m of orchards and 250 m of a forest fragment
 (Figure 1), which have diverse plant and pollinator communities (Kammerer
 et al., 2016). Often orchards rely, in part, on managed honey bee colonies
 for pollination, which have the potential to negatively impact native bee
 populations (Mallinger et al., 2017). However, our sampling sites did not
 have managed honey bee hives within 2 km and growers managing the adjacent
 orchards had not rented honey bees for at least 15 years.
 Our bee monitoring traps were located within perennial wildflower
 strips approximately 50 m x 10 m in size that were sown between 2-3 years
 before the beginning of our study. Wildflower sites used in this study
 were established and managed using the specific planting guidelines
 developed by the Pennsylvania USDA-NRCS and the Xerces Society for
 Invertebrate Conservation (NRCS, 2011). They were sown with 21 species of
 native forbs and grasses sourced from a local native seed supplier (Ernst
 Conservation Seed, Meadville, PA 16335). All wildflower sites were mowed
 once a year and received spot sprays of common selective herbicides to
 control non-native plants as needed. <strong>Bee
 collections</strong> We trapped bees continuously
 from April to October from 2014 to 2019 using Blue Vane traps (BanfieldBio
 Inc., Woodinville WA). A previous study in this region showed that Blue
 Vane traps collect a higher abundance and total richness of bees than
 colored bowl traps, also called pan traps (Joshi et al., 2015). Although
 the overall community composition of bees captured in Blue Vane traps was
 different from bowl traps, nearly all species were more likely to be
 captured in Blue Vane traps over bowls, except some Andrena and
 Lasioglossum species (Joshi et al., 2015). In our study, Blue Vane traps
 were filled with about 7 cm of 60% ethylene glycol (Supertech® Wal-Mart
 Stores, Inc., Bentonville, AR), hung from posts about 1.5 m off the
 ground. At each of our 8 locations, we placed 2 traps 25 m apart. Traps
 were left outside continuously from April to October every year and traps
 were replaced each year in case wear over time decreased their
 attractiveness. Each week, all specimens were removed and the ethylene
 glycol was replaced. Bee specimens were separated from other insects
 collected in the traps and stored in 70% alcohol until they were washed,
 pinned, and labeled. All bees were identified to the species level except
 14 individuals that were removed from analyses because of uncertain
 species-level identification. For bee identification, we used published
 dichotomous keys (Mitchell, 1960, 1962; Michener et al., 1994, Michener,
 2000) and various interactive bee identification guides available at
 Discover Life (http://www.discoverlife.org). Species identifications were
 conducted by David Biddinger (Pennsylvania State University), Robert Jean
 (Senior Entomologist, Environmental Solutions and Innovations, Inc.),
 Jason Gibbs (University of Manitoba), and Sam Droege (United States
 Geological Survey). All specimens from this study are stored at the
 Pennsylvania State Fruit Research and Extension Center, Biglerville, PA,
 or the Frost Insect Museum at Pennsylvania State University, University
 Park, PA.