Prairie Naturalist Shianne E. Lindsay and Autumn H. Smart 2025 No. 57 39 2025 PRAIRIE NATURALIST 57:1–20 Plant-bee interactions within pollinator habitats embedded in eastern Nebraska agroecosystems Shianne E. Lindsay and Autumn H. Smart Abstract–In the Great Plains region of the United States, land use change continues to negatively affect wild bee communities by limiting the availability of food and nesting resources. Concurrently, there is limited research describing bee species preferences for flowering plant species, including seasonal preferences. We monitored and surveyed previously established pollinator habitats in eastern Nebraska throughout the growing season for 2 years to assess bee-plant interactions of both honey bees and wild bee species. We observed seasonal variability in forbs, where abundance and species richness were generally higher in the early and mid-seasons, but we did not observe seasonal differences in bee abundance or bee species richness. We measured resource use to highlight plant species used by wild bees and honey bees throughout the growing season. Forb species utilization varied by bee group, where wild bees most preferred Oligoneuron rigidum (L.) Small (Stiff Goldenrod), Helianthus annuus L. (Annual Sunflower), and Ratibida pinnata (Vent.) Barnh. (Grey-headed Coneflower), while honey bees preferred Asclepias syriaca L. (Common Milkweed), Polygonum pensylvanicum L. (Pennsylvania smartweed), and Annual Sunflower. Our observations of plant-pollinator associations indicated minimal resource use overlap between honey bees and wild bees. Three bee species of conservation concern were encountered on our transects, including Megachile rugifrons Smith (Rugose-fronted Resin Bee), Bombus fraternus Smith (Southern Plains Bumble Bee), and B. pensylvanicus De Geer (American Bumble Bee). This study provides insight into the seasonal utilization of resources occurring among bee species within established pollinator habitats in eastern Nebraska. These findings will assist in improving and refining pollinator habitat seed mix designs to provide high quality, season-long, pollinator habitats within Midwestern working landscapes. Keywords: Wild bees, flowering plants, pollinator habitat, Great Plains, Nebraska, tallgrass prairie Introduction There is growing evidence documenting declines in populations of bee species, including those related to anthropogenic land use change and habitat fragmentation (Cariveau and Winfree 2015, Kammerer et al. 2021, Otto et al. 2016). Among agricultural habitats, the degradation, conversion, and fragmentation of natural and semi-natural habitat (Kremen et al. 2002, Richards 2001) via loss of flower-rich landscapes (Goulson et al. 2008) negatively affects abundance and richness of bee species (Winfree et al. 2009). In the United States, approximately 17% of the land base is in crop production (Bigelow and Borchers 2017), and numerous crops benefit, and are benefited by, wild bee pollination (Losey and Vaughan 2006, Kremen 2008). However, fragmented and isolated habitats, such as those that occur within many agricultural systems, are associated with decreased pollinator abundance, species richness, and functional diversity when compared to intact natural and semi-natural lands (Evans et al. 2018, Ewers et al. 2006, Vickruck et al. 2019). Declining pollinator abundance and diversity can negatively impact plant reproductive success by reducing seed set potential (Steffan-Dewenter and Tscharntke 1999) even as agricultural crops located near natural and semi-natural areas may achieve higher crop yields (Kremen et al. 2002, 2004; Mallinger et al. 2019a, Winfree et al. 2007). These findings highlight that agroecosystems are vital to addressing bee declines, and that less fragmented landscapes, containing intact pollinator habitat, have great potential to benefit both wild bee populations and agricultural productivity. Pollinator habitat establishment among agroecosystems typically includes non-crop herbaceous buffer strips around and between fields, roadside plantings, and management, and seeding of habitat on low-productivity and non-farmable private parcels (Decourtye et al. 2010, Haaland et al. 2011, Wratten et al. 2012). Maintenance of hedgerows, trees, and shrubs around fields can serve as fire and wind breaks, pesticide drift barriers, and refuge for woodland edge species (Boutin and Jobin 1998; Corbit et al. 1999; Morandin and Kremen 2013a, b). Within fields, the planting of cover crops that provide pollinator resources within farmable fields (Altieri 1999, Mallinger et al. 2019b) has been shown to add increased value to agricultural landscapes. There is increasing awareness and urgency to understand local plant-pollinator interactions so that pollinator-utilized seed mixes can be selected to maximize their potential benefits. In relation to plants that support pollinators, the terms “beneficial” and “recommended” are generally understood to relate to forbs on which bees are observed. A resource may be considered preferred when it receives more visitation than would be expected relative to its abundance (Bartomeus et al. 2016, Simanonok et al. 2021). Not only is understanding bee utilization and preference of forbs critical for provisioning effective habitat, but it is also critical in elucidating changes in season forage preferences in temperate climates (Simanonok et al. 2021). In such climates, both wild bee and plant phenology change through time, and many adult bee life stages are linked to those of their preferred host plants (Bendel et al. 2019, Wood et al. 2018). Research, based on field-derived data that account for known shifts in plant and bee phenology, is needed to inform conservation plans and habitat designs that provide plants utilized by wild bees over the entire growing season (Vaudo et al. 2015, Williams and Lonsdorf 2018). The Midwestern U.S. is a critical region for studying and supporting bees and other pollinators (Hellerstein et al. 2017; Koh et al. 2016; Otto et al. 2016, 2018). Nebraska is home to roughly 400 wild bee species with diverse life history traits and varied susceptibility to environmental stressors (Ascher and Pickering 2020). The state has experienced substantial land use change over time, including grassland habitat loss and conversion due to the intensification of row crop agriculture and infrastructure (Otto et al. 2016, Wright et al. 2017, Wright and Wimberly 2013). The larger region also serves as a summer foraging ground for nearly ⅓ of all commercial honey-producing and pollinating colonies in the U.S. (USDA-NASS 2020), and is home to several bumble bee species that are endangered or of conservation concern, including Bombus affinis Cresson (Rusty-patched Bumble Bee), Bombus fraternus Smith (Southern Plains Bumble Bee), Bombus pensylvanicus De Geer (American Bumble Bee), Bombus occidentalis Greene (Western Bumble Bee), and Bombus fervidus Fabricius (Yellow Bumble Bee; Grixti et al. 2009, Lamke et al. 2022, Rosenberger and Conforti 2020). Despite the significance of Midwestern U.S. natural and semi-natural habitats to support bee species and many other wildlife taxa, the region has continued to experience substantial land use change over time, resulting in losses of suitable bee habitat across the region (Hellerstein et al. 2017, Koh et al. 2016, Otto et al. 2016). For this study, we conducted seasonal bee biodiversity and floristic surveys among pollinator habitat patches located within agricultural landscapes of eastern Nebraska in order to 1) describe seasonal and interannual forb abundance and species richness, 2) describe seasonal and interannual bee abundance and species richness, 3) illustrate seasonal foraging patterns of honey bees and wild bee species, and 4) derive relative forb utilization preferences by honey bees and wild bees. Methods Study locations During the springs of 2021 and 2022 private lands providing a variety of pollinator habitat types were identified and selected based on the following criteria: 1) enrolled habitat size greater than 1.2 hectares (3 acres), 2) habitat age 3–5 years post planting, and 3) located in eastern Nebraska. Those lands included 1) Bee and Butterfly Habitat Fund sites (BBHF, nsites = 8, www.beeandbutterflyfund.org/); 2) Conservation Reserve Program sites (CRP, practice CP-42, Pollinator Habitat, nsites = 4, www.fsa.usda.gov/programs-and-services/conservation-programs/crp-practices-library/index); 3) expired CRP field sites (nsites = 1); 4) those having seeded the Stock Seed Pollinator Mix (SSPM, nsites = 1; www.stockseed.com/Shop/wildflower-mixtures/stock-s-pollinator-mixture). The BBHF in St. Paul, Nebraska provides landowners with pollinator seed mixes and technical assistance for project establishment and management. Stock Seed Farms, located in Murdock, Nebraska, is a local vendor growing and selling native grass and forb seed mixes to private landowners and also mixing seed for national USDA conservation programs. A total of 10 counties were represented among the 14 distinct sites in the final selection. The distance between any 2 sites ranged from 9.18 to185.18 km, well outside the typical flight range for bees. Surveys occurred at the 14 sites across 2 years (10 sites in 2021 and 9 sites in 2022), wherein we visited each site 3 times per growing season. Sites C, I, L, M, and N were surveyed in both years, while sites B, D, E, G, and J were dropped for the 2022 study year in exchange for sites A, F, H, and K. Exchanging one site for another between years occurred for a variety of reasons such as an inability to contact landowners during the subsequent year, change in land ownership, change in land use, or due to excessive travel distance. Plant-bee surveys Plant-bee interaction data were collected at each site visit along 3 transects measuring 2 m in width by 20 m in length. Each transect was considered to be a single 2×20 m plant-bee survey, wherein the species identification and number of stems of all blooming forbs were recorded along with any associated bee visitations to those plant species during a 10-minute search period. As flowering plants tended to occur in a patchy and sometimes sparse distribution, transect starting points and directions were selected semi-randomly to ensure encounter of actively blooming plants within each site. Upon arriving at a site, surveyors first visually assessed whole-site flowering plant abundance and richness, and subsequently transect starting points were determined to maximize plant abundance and richness encounter rate. Surveys occurred 3 times per growing season, spaced approximately five weeks apart during the expected peak bloom periods in each primary sub-season: early (8–23 June), mid- (20–28 July), and late (31 August–10 September) seasons. In total, 57 total site visits were completed, amounting to 171 transects (at 3 transects per site per visit) across the two years of the study. Actively blooming flowers were identified to species in the field using the iNaturalist/SEEK app, wildflower field guides (Newcomb 1989, Peterson and McKenny 1975), and by examination of site-level seed mix lists. We conducted transects when ambient temperatures were greater than 15.5° C, wind speeds were less than 18 km per hour, relative humidity was between 30–72%, and under a variety of cloud covers, ranging from overcast to clear skies. Surveys were conducted between the hours of 0900 and 1600. A flowering stem was defined by the point at which the stem, containing at least 1 actively blooming flower, met the soil regardless of the number of floral heads or inflorescences present on the stem. Due to variation in seed mix design from program designators, some species were intentionally seeded at some sites, while the same species may have been wild or considered volunteer at other sites. Therefore, observed blooming plants were cross-referenced with seed mix lists for each site to determine whether they were seeded or volunteer species. The Lady Bird Johnson Wildflower Center Database (wildflower.org) and the USDA Plants database (USDA-NRCS 2023) were used to standardize scientific and common names, growth frequency, and indigenous status relative to the United States. Along each transect, bee sampling was accomplished by employing 3 standard techniques during 10-minute timed searches: 1) aerial sweep nets were used over dense patches of a flower species (e.g. Alfalfa and vetches), or particularly tall and hard to reach flowers (e.g., sunflower, cup plant); 2) 50-ml falcon tubes were used to collect foraging bees on all other individual flowers; and 3) visual observations were used to record flower visits by Apis mellifera L. (Western Honey Bee) and Bombus spp. (Bumble Bee) queens, (i.e., no A. mellifera or Bombus queens were collected in this study). Wild bees were only captured when they were observed on flowers, presumably foraging for nectar or pollen. Wild bee specimens were pinned and identified at the University of Nebraska-Lincoln Bee Lab by S. Lindsay utilizing dichotomous keys (M. Arduser Missouri Department of Conservation (retired) Saint Charles MO 2022 unpublished data, Ascher and Pickering 2020, Michener 2007, Michener et al. 1994). Physical voucher specimens for all encountered wild bee species are housed at the University of Nebraska-Lincoln’s Nebraska Hall and all databased records, including all bees collected and their floral associations, are available via SCAN (https://scan-bugs.org/portal/, Collection: UNSMe). Analysis All analyses were conducted using R version 4.2.2 (R Core Team 2022). Individual transects (n = 3 per site visit) were used as replicates of each field site within each season (early, mid-, and late) and year. Flowering plant stem abundance per transect was determined as the mean number of flowering stems of all plant species observed among the 3 transects occurring at each site during each seasonal (n = 3) sampling event per year. Similarly, bee abundance (as bees per transect) was determined as the mean number of bees among the 3 transects occurring at each site during each seasonal (n = 3) sampling event per year. Likewise, species richness (both plants and bees) was determined as the mean number of species observed among the 3 transects occurring at each site during each seasonal (n = 3) sampling event per year. Flowering plant stem abundance, bee abundance, and bee species richness were each used as response variables in linear mixed effect modeling (lme4 package) to examine fixed (season and year) and random (site) effects in the study. Count data for both bees and plants were log-transformed to normalize their distributions prior to statistical analyses. To illustrate interactions between plants and bees, bipartite alluvial plots were created using R packages ggplot2 and ggalluvial (R Core Team 2022). Bipartite alluvial plots were created seasonally for the top 20 interactions between plants and bees. A floral preference index (i.e., resource use index) was used (Johnson 1980, Williams et al. 2011) wherein all forb species with n > 1 observed bee visit and n > 20 total stems counted (summed among all seasons and years) were ranked (1−n) relative to their number of bee visits. Forbs were also ranked from highest to lowest number of blooming stems observed (1−n, summed among all seasons and sampling years). The floral preference index was derived as the difference between the bee visitation rank and the stem abundance rank, where a greater difference indicated greater preference for a given forb by bees (wild and honey bee preference indices were each generated separately). Tied rank differences were allowed to occur and were left as such. Results Forbs A total of 101 species of flowering forbs were observed over the two-year study, totaling 47,207 blooming stems among all sites, transects, seasons, and years. The number of blooming stems per species on an individual transect ranged from 1 (n = 50 species in the dataset) to 1,500 (Medicago sativa L., [Alfalfa]). The sum number of stems per individual site ranged from 116 to 4,529, while plant species richness ranged from 2 to 21 species (SI Table 1). There was a significant positive correlation (t58 = 3.21, r = 0.39, P = 0.002) between flowering plant stem abundance and flowering plant species richness among all sites, seasons, and years, meaning that as the abundance of flowering plant stems increased in a sample (site by season by year), so too did the species richness within that sample (SI Fig. 1). We observed a significant interaction between season and year relative to forb stem abundance (F2,54 = 3.14, P = 0.05) where the early and mid-season surveys in 2021 had higher stem abundances compared to those conducted in the late season, but stem abundance did not significantly vary among seasons in 2022 (Fig. 1). Forb stem abundance did not vary (F2,57 = 0.79, P = 0.46) across the 3 conservation programs we evaluated: BBHF, CRP, and SSPM. Plant species richness varied by season (F2,44 = 7.23, P = 0.002) where the mid- and late seasons were statistically different, and year (F1,54 = 18.68, P < 0.0001; Fig. 2). We did not observe a statistically significant interaction between season and year. Further, plant species richness did not vary across BBHF, CRP and SSPM (F2,57 = 1.13, P = 0.33). Within each year, stem abundance and species richness through time varied among sites (Fig. 3). The highest number of blooming plant stems per transect among sites, seasons, and years occurred in the early season of 2021 at site N (CRP-CP42), sites C and E (BBHF), and again in the mid-season of 2021 at site C (Fig. 3). The lowest plant stem abundances occurred in the late season of 2021 (site I: BBHF), mid-season of 2022 (site M: retired CRP), and late season of 2022 (site H: BBHF, site K: CRP-CP42). The highest plant species richness observed among sites, seasons, and years occurred in the mid-season of 2021, including at sites B and C (BBHF) and site K (CRP-CP42). Flowering plant species richness was lowest in the early (site F: CRP-CP42, site I: BBHF) and late (site H: BBHF) seasons of 2022 (Fig. 3). Of all plant species encountered throughout the study (n = 101), 73.2% were perennial species (n = 74), 10.9% were biennial species (n = 11), and 15.8% were annuals (n = 16) (SI Table 2). Most species (69.3%, n = 70) were native to Nebraska (USDA-NRCS 2023, wildflower.org). Of the blooming plants encountered, 62% were intentionally seeded in the given site’s habitat. Of plants encountered, 31% were volunteer species which included a mix of native volunteers and non-native weeds such as thistles (SI Table 2). The few remaining plants could not be verified due to the absence of a seed mix list (at site M), which was a retired CRP field that remained fallow and consisted of seeded wildflowers and other volunteer species. Four plant species had a 100% establishment rate (i.e., they were detected at every site where they occurred in a seed mix): Annual Sunflower, Silphium integrifolium Michx. (Entire-leaved Rosinweed), Melilotus officinalis (L.) Lam. (Yellow Sweet Clover), and Prunella vulgaris L. (Self-heal). There were 5 more plant species that had >80% establishment rate: Ratibida pinnata (Vent.) Barnh. (Grey-headed Coneflower), Heliopsis helianthoides (L.) Sweet (False Sunflower), Trifolium pratense L. (Red Clover), Solidago canadensis L. (Canada Goldenrod), and Achillea millefolium L. (Common Yarrow). Fifteen additional plant species were observed on 50–79% of sites where they were seeded, while 24 species were observed on <50% of sites where they were seeded, but at least once (SI Table 2). Among the 14 sites and 2 years of the study, an average of 33% of the plants originally seeded were observed blooming (minimum: 23% at site J, maximum: 63% at site N). Overall, 50 non-annual plant species (41% of all plants on a seed mix list) were seeded but not observed during our study. Bees A total of 1,188 individual bees were either collected (n = 832) or observed (honey bees, bumble bee queens, n = 356) during the study, representing 5 families, 27 genera, and 73 species. As with the flowering plants, we found that the abundance of bees and bee species richness were positively correlated (t58 = 7.65, r = 0.71, P < 0.0001) among all sites, seasons, and years, meaning that as the abundance of bees increased in a sample (a site by season by year) so too did the species richness within that sample (SI Fig. 1). Bee abundance did not vary by season (F2,56 = 1.15, P = 0.33), year (F1,56 = 0.18, P = 0.68), or program designation (F2,57 = 0.22, P = 0.80). Likewise, bee species richness did not statistically vary by season (F2,56 = 2.3, P = 0.11), year (F1,56 = 0.02, P = 0.89), or program designation (F2,57 = 0.19, P = 0.83). The highest bee species richness among sites by season and year occurred at site K (mean = 14 species, CRP-CP42) in the late season of 2022, site G (mean = 13, BBHF) in the late season of 2021, site C (mean = 12 species, BBHF) and site M (mean = 12 species, CRP) in the mid-season of 2021, and site L (mean = 12, SSPM) in the mid-season of 2022 (Fig. 4). The lowest bee species richness occurred at site L (mean = 1, SSPM) in the late season of 2021, site N (mean = 1 species, CRP) in the early season of 2022, and site B (mean = 1, BBHF) in the early season of 2021 (Fig. 4). Apidae was the most abundant (n = 677) and species rich (n = 30) family when including honey bee observational counts, representing 57% of all bees and 41% of all species observed. Halictidae was the next most abundant (n = 400) and species rich (n = 22) family, representing 34% of all bees. Ground nesting bees were the most common of the wild bee species collected, representing 70% of species richness and 62% of individual bees. The majority of observed bee species were solitary (70%). Over 78% of species observed were polylectic, or generalist foragers. We encountered 3 wild bee species recognized as endangered or imperiled, classified by G2 or G3 conservation status (NatureServe.org). We collected a single female Megachile rugifrons Smith (Rugose-fronted Resin Bee) at site L during the mid-season on 22 July 2022 (SI Tables 2 and 3). At the time of collection, the bee was visiting flowers of Eryngium yuccifolium Michaux (Rattlesnake Master). We collected 3 B. fraternus (Southern Plains Bumble Bee) during both the mid- and late seasons of 2021: 1 female on Monarda fistulosa L. (Wild Bergamot), 1 male on Symphyotrichum novae-angliae (L.) Nesom (New England Aster) at site G), and during the late season of 2022: 1 female on Helianthus grosseserratus Martens (Sawtooth Sunflower) at site C. Finally, we encountered 38 B. pensylvanicus (American Bumble Bee) during our surveys. Individuals were collected on 13 different plant species (SI Tables 2 and 3) among 9 different sites in the mid- and late seasons of 2021 and 2022. Plant-bee interactions While both abundance and richness of plants and bees, respectively, were positively correlated, we did not detect significant relationships between bee abundance and plant stem abundance (t58 = −0.91, r = −0.12, P = 0.37), bee species richness and plant stem abundance (t58 = −0.12, r = −0.02, P = 0.90), bee abundance and plant species richness (t58 = −0.89, r = −0.12, P = 0.38), or bee species richness and plant species richness (t58 = −0.03, r = −0.004, P = 0.98; SI Fig. 1). Of the 101 plant species observed on transects, 63 species (62%) were visited by bees. The highest number of bees per stem occurred on Silphium laciniatum L. (Compass Plant, mean = 1.2 bees per stem), but overall bee species richness was relatively low (3 species of bees). The highest bee species richness was recorded on Canada Goldenrod (21 species of bees) and on False Sunflower (21 species of bees), but both had relatively low numbers of bees per stem abundance, at 0.1 and 0.02 bees per stem, respectively (Fig. 5). To discern seasonal community connections, we examined the top 20 plant-bee interactions that occurred within each season. Among the top 20 plant-bee interactions in the early season (Fig. 5), Penstemon digitalis (N.) Sims (Foxglove Beardtongue) had the most observed bee visitations (51 bees from 3 groups: Bombus spp. queens (37), Ceratina calcarata Robertson (Wide-legged Little Carpenter Bee; 10), Hyleus mesillae Cockerell (Mesilla Valley Yellow-faced bee; 4)), followed by Common Milkweed visited by 37 honey bees, and Yellow Sweet Clover observed being visited by 24 honey bees and 8 Lasioglossum imitatum Walker (Bristle Sweat Bee). Among the top 20 plant-bee interactions occurring in the mid-season (Fig. 6), Wild Bergamot had the most observed bee visitations (97) from 4 groups: honey bees (45), Bombus spp. including queens (29), Lasioglossum imitatum (17), and Melissodes communis Cresson (Common Long-horned Bee; 6); followed by Chamaecrista fasciculata (Michx.) Greene (Partridge Pea), which was visited by 26 honey bees and 5 Bombus griseocollis De Geer) Brown-belted Bumble Bee); and finally Prairie Coneflower which was observed being visited by 19 Halictus ligatus Say (Ligated Gregarious Sweat Bee) and 7 Triepeolus lunatus Say (Crescent-shaped Cuckoo Nomad Bee). In the late season (Fig. 7) the top 20 plant-bee interactions included Pennsylvania Smartweed which had the most observed bee visitations (79 honey bees), followed by Canada Goldenrod visited by 25 honey bees, 20 Halictus confusus Smith (Confused Sweat Bee), 14 Lasioglossum Dialictus sp., and 9 Augochlorella aurata Smith (Golden Sweat Bee), and finally Stiff Goldenrod observed being visited by H. ligatus (18), Lasioglossum imitatum (9), and Lasioglossum Dialictus sp. (7). Forty plant species, with greater than 20 blooming stems observed, were preferred by wild bees (Table 2, Abundance Preference > 0). Stiff Goldenrod (native), Annual Sunflower (native), and Grey-headed Coneflower (native) ranked highest relative to wild bee abundance rank difference. There were 10 plant species that were non-preferred for supporting wild bee abundance (Table 2, Abundance Preference < 0), including Alfalfa (non-native), Vicia villosa Roth (Hairy Vetch, non-native), and Partridge Pea (native). Thirteen plant species were considered preferred by honey bees (Table 3, Abundance Preference > 0), including Common Milkweed (native), Pennsylvania Smartweed (native), and Annual Sunflower (native). There were 8 plants that were considered non-preferred (Table 3, Abundance Preference < 0) by honey bee, including Alfalfa, Hairy Vetch, and Foxglove Beardtongue (native). Hibiscum trionum L. (Flower-of-an-hour, non-native), ranked as preferred. However, it was below the threshold of 20 stems, so its preference cannot be confirmed here due to its low stem abundance among surveys. Discussion Due to the declines that many wild bee populations have experienced globally (Potts et al. 2010, Zattara and Aizen 2021), it is of increasing importance to incorporate research-based considerations into conservation plans and landscape designs. Therefore, it is crucial to understand seasonal flower selection by bees to maximize the effectiveness of conservation efforts. The results of this study document bee species richness and abundance on pollinator habitats in agricultural areas of Nebraska and highlight selection of pollinator-attractive forbs by bees throughout the growing season. All sites surveyed represented pollinator-focused habitat establishments within agroecosystems in the tallgrass prairie (TGP) region of the United States. These sites showed a general pattern of highest forb species richness and stem abundance in the early and mid-seasons, with lower richness and abundance in the late seasons. This is consistent with other observations of plantings across the TGP region that favor mid-summer forb species in seed mixes (Delaney et al. 2015, Smart et al. 2021). The most abundant (highest number of stem counts) mid-summer species included Wild Bergamot (native), Hairy Vetch (introduced), Partridge Pea (native), Alfalfa (introduced), and Red Clover (introduced). Wild Bergamot contributed substantially to bee richness and abundance in the mid-season (Fig. 6) but was not calculated as a preferred resource for wild bees overall (Table 2). Seed mixes favoring mid-season bloom over the early and late seasons could result in bee-plant community mismatch, as adequate resources may be absent for initial early-season nest site selection and late-season nest provisioning (Thomas and Kunin 1999). The seasonal peak in bee abundance occurred during the late season (August–September). A significant portion of this abundance was driven by honey bees (Fig. 7). However, Bombus and halictid species were also abundant during this time and continued to be through the mid- and late seasons. This peak in abundance is likely driven by the continuous growth of honey bee and bumble bee colonies through the growing season and the final generation emergence in the late summer at which time new bumble bee foundresses and males emerge to mate (Oertli et al. 2005). The turnover of bee species over the duration of the summer is due to specific life histories that vary by species. The activity periods of wild bees are limited to only a few weeks or even days in some species (i.e. Andrena spp.; Danforth et al. 2019, Michener 2007), while others may exhibit frequent activity for months (e.g. H. ligatus, Bombus spp.). For example, Minckley et al. (1999) reported a median similarity of only 35% of bee species between sampling periods and similar results have been observed by other researchers (Williams et al. 2001). In our study, bee species richness peaked in the mid-season (July) at the same time as plant richness and abundance, and was likely driven by phenological overlaps in the bee and forb communities. Previous studies have documented greater species turnover by season within specific ecological categories. For example, the rate of turnover for oligolectic species may be higher than generalist species between seasons due to their phenological overlap with host resources. By sampling through a seasonal gradient, we were able to encompass the diversity and turnover in bee community composition among the surveyed habitats through time (Table 1, Oertli et al. 2005). During our surveys, we encountered several taxa of conservation concern. We collected a single female Megachile rugifrons (on Rattlesnake Master), which is a rare bee species with declining populations known previously (in Nebraska) only from 2 confirmed records: 1 from Cedar Point Biological Station in 1988 and 1 from Mahoney State Park in 2011 (Ascher and Pickering 2020). Further, M. rugifrons is known only from prairie remnants and conservation lands, highlighting the importance of human-designed and implemented pollinator habitats like those examined in our study in supporting rare and declining bee species. Two species of Bombus, B. fraternus (Hatfield et al. 2014) and B. pensylvanicus (Hatfield et al. 2015), collected in our study are listed as endangered or vulnerable, respectively, under the International Union for Conservation of Nature (IUCN) Red List criteria (IUCN 2023) but currently have no federal protections and were collected among several sites, seasons, and on various plant species (SI Tables 2 and 3). Another important finding in our study was that often the most abundant forbs, as determined via total stem counts, were commonly least preferred by bees. This mismatch is highlighted in the examples of Alfalfa and Partridge Pea which ranked first and third by total stem abundance among all plant species observed, yet ranked as 2 of the least preferred species (Tables 2 and 3) by both honey bees and wild bees. Both species were commonly included in the seeding mixes among our study sites and they undoubtedly provide season-long food resources for bees, have climate-hardy growth habits, and economical seed costs. However, they were not preferred by either wild bees or honey bees. Previous studies have documented similar trends, finding that alternative sources of pollen and nectar may limit bee visitation (Bohart 1957, 1958) and ultimately impact indices of bee preference like the one used in this study (Pizante et al. 2023). For example, Bohart (1958) found that only when competing pollen sources are nearly eliminated over a large area is the number of bees foraging on Alfalfa noticeably increased. Related, some plants deemed “unpreferred” (e.g. Alfalfa, vetches, clovers) in our study may primarily be so due to their high flowering stem abundances, i.e. by calculation they are not preferred even though many bees were observed on them and, en masse, they provide substantial food resources for bee communities living among working lands. We emphasize caution in using the preference ranks found in Tables 2 and 3 as generalizable because bee preferences are context-dependent, and there are other approaches to determining preference (Pizante et al. 2023). Interestingly, Common Milkweed was the most preferred plant species by honey bees and was preferred by honey bees more than wild bees (Tables 2, 3). In addition to honey bee visitation, we observed 9 distinct wild bee species on Common Milkweed including some relatively uncommon species such as Anthophora bomboides Kirby (Bumblebee-like Digger Bee) and Nomia nortoni Cresson (Norton’s Alkali Bee). Although milkweed does not serve as a pollen source for bees due to the structure of the pollinia, it is a significant source of nectar (Southwick 1983, Theiss et al. 2007). We saw strong differential landscape use among honey bees and wild bees, which supports findings from previous studies (Otto et al. 2021, Rollin et al. 2013, Simanonok et al. 2021). There was relatively minimal overlap between honey bee and wild bee plant utilization throughout the growing season (Figs. 5–7). In the early season, Common Milkweed and Yellow Sweet Clover were important targets for honey bees, while Foxglove Beardtongue received significant visitation from wild bee species, including bumble bee queens. In the mid-season, Wild Bergamot was highly visited by both honey bees and wild bees, boasting a high bee abundance and wild bee species richness in visitations during those times. In the late season, sunflower and goldenrod species provide significant resources to wild bees and to a lesser extent, honey bees, which were seen abundantly visiting Pennsylvania Smartweed. These findings indicate there are opportunities for improving pollinator and conservation habitat seed mixes by understanding which forb species were most and least utilized by different bee groups, and which forb species may result in reduced overlap between potentially competing bee species throughout the season. The main limitations we encountered in this study included 1) the snapshot sampling periods (i.e. one site visit per season) and 2) the narrowed sampling range (June–September) to estimate peaks within the growing season. It is likely that some plant and bee species were missed spatially or temporally during the surveys. For example, some bees within the region, e.g. Andrena spp., become active and then dormant prior to the initiation of our sampling each spring. These species are tightly aligned with the phenology of their host species, especially blooms of woody trees and shrubs (e.g., Salix spp., Acer spp., and Malus spp.). Further, our active collection methods may have resulted in missed bees during collection periods due to 1) scaring them away while searching transects and 2) visually missing bees, especially those that are cryptic in coloration or small in size. Loss of high-quality habitat due to agricultural intensification is a leading cause of bee declines globally (Potts et al. 2010, Zattara and Aizen 2021). In this study we documented seasonal bee communities within established pollinator habitats among an agriculturally dominant landscape. Fluctuations in bee richness and abundance across the growing season and years highlight the need to supply a species-rich community of foraging resources throughout the growing season. Effective habitat establishments require a deep understanding of species requirements throughout their lifecycles and life histories. The range of species needs, even within a target group such as pollinators, is widely diverse. Therefore, further research is needed to understand areas of best fit for pollinator habitat restoration, species-specific needs and preferences, and management. Tailoring conservation goals and habitat programs to prioritize specific bees or to target plants preferred by managed (i.e. honey bees) or non-managed bee species may be a useful tactic for reaching both agricultural and conservation goals. Acknowledgements The University of Nebraska-Lincoln Agricultural Research Division and the Bee and Butterfly Habitat Fund provided funding to support this work. 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