DOI: 10.5061/dryad.66t1g1k3s
title: The abundance and diversity of native bees in prairie agroecosystems Samantha Morrice thesis raw data

description: Habitat loss due to agricultural intensification has negative implications
 for native bee communities throughout Western Canada. Wetland remnants are
 a common feature within the Prairie Pothole Region of Saskatchewan and are
 threatened due to continued conversion to agricultural land. Approximately
 sixty-one million acres of land are dedicated to agriculture in
 Saskatchewan. Wetlands and field margins in this region are embedded in
 these agricultural matrices and may act as important nesting and floral
 resources for many native bee taxa. The purpose of this study was to
 determine whether conserved habitats, such as wetlands and field margins,
 in highly cultivated landscapes support native bee and pollinator
 diversity, which is expected to be ecologically and economically
 beneficial. I also examined differences in bee abundance and diversity
 across three crop types to explore the roles different crop types might
 play as a habitat or feeding resource for native bees. Bees were sampled
 from wetland and field margins into the surrounding cropland across two
 growing seasons in three crop types (canola, cereals and semi-natural
 re-seeded forage) to quantify the role that wetlands, field margins and
 crop types play in supporting native bee populations. I found that the
 diversity and abundance of native bees collected from natural and
 semi-natural edge habitat was higher than that collected in-field. Areas
 with a higher availability of nesting resources tended to support a higher
 diversity of bee genera. Unmanaged semi-natural re-seeded forage sites
 supported a higher abundance and diversity of bees than canola and cereal
 crops. Finally, we found that bee community structure differed
 significantly between years, likely due to differences in temperature and
 precipitation. Results of this study suggest that native bees may be using
 edge habitat for nesting and floral resources. Bees nesting in these areas
 may in turn provide pollination to agricultural crops through a
 “spill-over” effect. This project has improved our understanding of native
 bee communities and the value of management practices that promote
 sustainable agricultural production through pollination services. These
 results further support the need for management of agricultural cropland
 that preserves semi-natural habitat that is integral to native bee
 functional diversity.
description: Study Sites This survey took place in the
 summers of 2018 and 2019. Across the two field seasons bees were sampled
 from fifteen field sites between Peterson and Humboldt, in the Prairie
 Pothole Region of Saskatchewan (Table 1.1). Each sample site was one
 quarter section of land, five of which were re-seeded semi-natural forage
 grassland, five were seeded with insect-pollinated crops and five
 contained wind-pollinated crops. Sites were chosen using the Ducks
 Unlimited Canada conservation program database based on a series of
 criteria (Figure 1.1). Criteria considered in site selection included: the
 estimated proportion of wetland habitat within 1km buffer of a point at
 the center of each quarter section, that the location was adjacent to the
 road, the intended crop for that field at time of selection, and finally
 farmer participation. Crops were classified by their pollination mechanism
 and crop rotation took place between the 2018 and 2019 field seasons,
 therefore site classification changed between years. Sites where canola
 was planted were classified as insect pollinated, wheat and barley were
 classified as wind pollinated and forage sites were classified as mixed
 pollination. Table 1.1. Summary of crop type in each study
 site in 2018 and 2019. Site numbers correspond to the location of the
 study fields shown in Figure 1.1. 
   Crop Type 
 Site
 2018
 2019
 1 Forage Forage 
 2
 Forage Forage 
 3
 Forage Forage 
 4
 Forage Forage 
 5
 Forage Forage 
 6
 Cereal Canola 
 7
 Cereal Canola 
 8
 Cereal Canola 
 9
 Cereal Canola 
 10
 Cereal Canola 
 11
 Canola Corn 
 12
 Canola Cereal 
 13
 Canola Cereal 
 14
 Canola Cereal 
 15
 Canola Cereal 
  
      
      
      
      
      
      
      
      
 Field Sampling To measure the diversity and
 abundance of native bees, field surveys were conducted with the use of
 passive sampling methods to collect bees present in re-seeded semi-natural
 forage grassland and agricultural settings containing a wetland habitat in
 the summers of 2018 and 2019. Passive sampling methods included standard
 blue, yellow and white pan traps painted with UV paint (New Horizons,
 Upper Marlboro, MD) (Droege et al. 2017) and blue/yellow vane traps
 (Springstar Inc., St. Louis, MO, USA) (Appendix 1). Pan traps were sampled
 using adapted versions of the standardized method of monitoring bee
 populations by LeBuhn et al. (2015), the National Protocol Framework for
 Inventory and Monitoring of Native Bees (Droege et al. 2017), and sampling
 protocols from the Canadian Pollination Initiative by Corey Sheffield
 (2009). As there are biases in the genera caught by each trap type, both
 trapping methods were used to ensure adequate sampling of genera present
 in the area (Mogren et al. 2016). Blue/yellow vane traps are known to be
 attractive to large and common bees such as Bombus spp. and are also known
 to capture a high volume (Hall 2018). Blue, yellow and white pan traps, on
 the other hand, are known to capture smaller and more rare species of bee
 (Joshi et al. 2015). Abundance was quantified as the sum of individuals
 collected in the three pans (one of each colour) and vane traps at each
 position of the transect. Within each site, traps were
 spaced at 0m, 75m and 150m along two linear transects starting at the
 field or wetland margin extending into the field. During the 2018 field
 season, traps were also set at a 25m position, but were omitted in the
 2019 season to minimize unnecessary destructive sampling. Transects
 extended into the field such that the 150m traps were positioned within
 the crop (see Appendix 2 for site diagram). Wetland margins were defined
 as the vegetation within a 10m radius of a permanent wetland (pothole)
 that was undisturbed by agricultural management. Field margins were
 defined as a strip of natural or semi-natural vegetation located adjacent
 to a field, between a field and a road or along a fence line.  Pan and
 vane traps were place on two separate poles space 1m adjacent to one
 another. Pan traps were secured to poles by custom 3D printed holders that
 allowed height adjustment with respect to the crop canopy (Appendix 3).
 Pan traps remained in the field for twenty-four hours, while vane traps
 remained in the field for a seven-day period prior to collection.
 Collection took place over five sample periods throughout the growing
 season: pre-seed, post-seed, flowering, post-flowering and post-harvest.
 Bees from the pre-seed (May) and flowering period (July) from both seasons
 were used in the analysis for this project. Timing of sample periods was
 dependent upon the growth of vegetation (percentage of crop flowering) and
 weather restrictions. The pre-seed period was defined as the period prior
 to a grower seeding the site and the flowering period was defined as the
 time in which &gt;50% of flowers were present in sites with flowering
 crops. Only zero metre traps were sampled in canola and cereal crops in
 the pre-seed period of both years, as seeding had not yet taken place and
 traps could not be set along the rest of the transect until this was
 complete. Therefore, only bees captured in 0m traps across all crop types
 were used for pre-seed analysis. Differences in the community composition
 between bees found in edge habitat to those found in the field were the
 primary interest for the flowering period, therefore, only bees captured
 in 0m and 150m traps were used for this analysis (bees captured in 75m
 traps were omitted). Native Bee
 Identification Bees collected from pan and vane traps
 were washed and pinned using methods adapted from Sam Droege (Droege et
 al. 2010) and the CANPOLIN Survey of Pollinator Diversity in Canada by
 Corey Sheffield (2009). Bees were then rinsed and stored in 70% ethanol
 until they were ready to be processed and identified.  
 Bees were identified to genus as very few species keys have been
 formed for western Canada, particularly for bees found in this study
 region. Additionally, most of the commonly used taxonomic keys for bees
 are to genus, and bee identification to genus is common for this type of
 study (Happe et al. 2018; Potts et al. 2005, O’Brien and Arathi 2018;
 Martins et al. 2018). Identification of bees to genus was performed using
 several taxonomic keys and identification tools including: The Bee Genera
 of Eastern Canada (Packer et al. 2007), The Bees of the World (Michener
 2000), Bumble Bees of North American (Williams et al. 2014), The Bees in
 Your Backyard (Wilson and Carril 2016), The Bees of the Eastern United
 States (Mitchell 1960 and 1962), The Solitary Bees (Danforth, Minckley and
 Neff 2019), and Discoverlife (Ascher and Pickering 2015). All specimens
 are stored in either the Prager Lab at the University of Saskatchewan or
 the Rehan lab at York University.