Data from: Bee-mediated pollen transport across five urban landscape features: Buildings are important barriers
Data files
Apr 25, 2025 version files 44.02 KB
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dye_counts.csv
22.94 KB
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dye_probability_vs_insect_visitation_rate.csv
170 B
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insect_visitation_estimate.csv
5.38 KB
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insect_visitation.csv
5.58 KB
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README.md
9.95 KB
Abstract
Urbanization alters insect pollinator diversity and foraging distances, while also providing novel pollinator habitats. Common landscape features that are characteristic of urban sprawl, such as roads and buildings, may alter the ability of insect pollinators to move and forage throughout the urban landscape. Given increased interest in urban pollinator conservation, more empirical information is needed about the spatial effects of cities on movement of pollinators and pollen.
In this study, we aimed to quantify the effects of common urban landscape features on insect pollinator movement. We focused on roads, buildings, forest fragments, lawns, and community gardens. We studied 5 community garden sites, and the landscape features surrounding them, in Raleigh, North Carolina, USA. To measure pollinator movement across each feature, we placed clusters of potted cucumber plants on either side of a feature and added fluorescent dye powder to the stamens of the flowers. After 7 hours, we collected and counted the number of fluorescent dye powder grains transferred to each cucumber stigma. We conducted 10-minute visitation observations at each cluster to assess the pollinator community and to assess whether low visitation was linked to low dye transfer.
Buildings had the lowest estimated dye transfer, roads and gardens were intermediate, and lawns and forest fragments had the highest estimated dye transfer. Although plants associated with buildings also had low visitation rates, visitation overall was a poor predictor of dye transfer.
The most common visitors observed were Apis mellifera, Bombus spp., and Xylocopa virginica, indicating our results are likely primarily representative of these large, generalist bee species.
Our study highlights the heterogeneity of urban spaces to pollinators. We demonstrate which features facilitate and inhibit movements of pollinators, and thereby provide an empirical basis to map and assess functional landscape connectivity. This information can help cities identify and create connected networks of habitat for essential pollinators using geospatial methods, and can inform research about resource accessibility and foraging energetics for urban pollinators.
Dataset DOI: 10.5061/dryad.w9ghx3g08
Description of the data and file structure
In this study, we aimed to quantify the effects of common urban landscape features on insect pollinator movement. We focused on roads, buildings, forest fragments, lawns, and community gardens. We studied 5 community garden sites, and the landscape features surrounding them, in Raleigh, North Carolina, USA. To measure pollinator movement across each feature, we placed clusters of potted cucumber plants on either side of a feature and added fluorescent dye powder to the stamens of the flowers. After 7 hours, we collected and counted the number of fluorescent dye powder grains transferred to each cucumber stigma. We conducted 10-minute visitation observations at each cluster to assess the pollinator community and to assess whether low visitation was linked to low dye transfer.
Files and variables
File: dye_counts.csv
Description:
Variables
- Column 1: Number designation for each row that was created in R after data cleaning and download
- Site: Name of site (sites 1 through 5).
- Date: Date of sampling per site (YYYYMMDD).
- barrier_crossed: Descriptor of what urban landscape feature an insect would have crossed to transfer dye onto a set of cucumber flowers. Categories are building, road, garden (community garden with culinary and ornamental plants), lawn (mowed turf, sometimes including small forbs), and forest (urban forest fragment).
- color_rcvd: The dye color transferred onto each cucumber stigma by insects. Color categories are blue, green, orange, pink, salmon1, salmon3, white, yellow.
- cluster: Categorical number designation according to each color added to cucumber flowers per site and date. All plants in a 'cluster' were placed together and were labeled by the researchers with the same color of dye. Cluster designations are nested within site and date.
- group: Categorical number designation according to which landscape feature separated cucumber clusters per site and date. A group could include two or three clusters (see Fig. 1 in the main paper). Group designations are nested within site and date.
- tube ID: Categorical ID number used to label and identify tubes of collected cucumber stigmas from 0 up. Each tube ID refers to a single stigma. Stigmas that received dye from more than one other cucumber group have multiple rows to represent the multiple colors of dye.
- grains dye: The number of grains of dye powder counted from each tube ID.
File: dye_probability_vs_insect_visitation_rate.csv
Description: Data sheet that combines the estimated marginal means (emmeans) results from dye transfer (probability of dye transfer across a landscape feature and standard error) and insect visitation observations (rate of insect visitation to landscape feature-associated cucumbers and standard error).
Variables
- feature: Urban landscape feature that was crossed by insects. Categories are building, road, garden (community garden with culinary and ornamental plants), lawn (mowed turf, sometimes including small forbs), and forest (urban forest fragment).
- rate: Insect visitation rate to landscape feature-associated cucumbers (visits per 10 min).
- rate_se: SE (standard error) of insect visitation rates per feature.
- prob: Fluorescent dye powder transfer probability per feature.
- prob_se: SE (standard error) of dye powder transfer probability per feature.
File: insect_visitation.csv
Description: Insect visitation observation counts per cucumber group, site, and date. Insects were identified on the wing to the taxonomic groups in columns 9:24 (Bombus:Toxomerus). A visit was tallied each time an individual landed on a cucumber flower.
Variables
- Site: Name of site (sites 1 through 5).
- Date: Date of sampling per site (YYYYMMDD).
- round: Month of sampling- either June or July.
- start time: Time at beginning of observation period (HH:MM); observations were 10 minutes each so each time period should be equal.
- end time: Time at the end of observation period (HH:MM)
- cluster: Number designation according to each color added to cucumber flowers per site and date. All plants in a 'cluster' were placed together and were labeled by the researchers with the same color of dye. Cluster designations are nested within site and date.
- M flwr: The number of male flowers the observer could see from their observation spot.
- F flwr: The number of female flowers the observer could see from their observation spot.
- Bombus: Number of Bombus spp. visits that were not identified to species level.
- B impatiens: Number of Bombus impatiens tallied.
- B gris: Number of Bombus griseocollis tallied.
- Apis: Number of Apis mellifera tallied.
- Megachile: Number of Megachile tallied (not identified to species level).
- Xylo. virginica: Number of Xylocopa virginica tallied.
- Lasioglossum: Number of Lasioglossum tallied (not idenitified to species level).
- Ceratina: Number of Ceratina tallied (not identified to species level).
- Halictus: Number of Halictus tallied (not identified to species level).
- Augo: Number of Augochlora/ Augochlorella tallied (not identified to species level).
- Skipper: Number of skippers (Hesperiidae) tallied (not identified to genus/species level).
- fly: Number of flies (Diptera) tallied (not identifies to family level).
- Polistes wasp: Number of Polistes wasps tallied (not identified to species level).
- June bug: Number of green June bugs (Cotinis nitida) tallied.
- yellow jacket: Number of yellow jackets (Vespula maculifrons) tallied.
- Toxomerus: Number of hoverflies (Toxomerus spp.) tallied.
File: insect_visitation_estimate.csv
Description: This dataset is a subset of insect visitation observation counts, where each group is represented by the cluster with the smallest number of visits. This dataset was used to determine the conservative estimate of rate of insect visitation that would have limited dye transfer across associated urban landscape features, and was derived from the insect_visitation.csv dataset. As in that dataset, insects were identified on the wing to the taxonomic groups in columns 12:27 (Bombus:Toxomerus). A visit was tallied each time an individual landed on a cucumber flower. One row has NA values since the cucumber pots were stolen before we could do insect visitation observations.
Variables
- Column 1: Number designation for each row that was created in R after data cleaning and download.
- Site.x: Name of site (sites 1 through 5).
- Date.x: Date of sampling per site (YYYYMMDD).
- SiteDateBarrier: Housekeeping variable that creates a unique ID for each combination of site, date, and barrier crossed.
- barrier: Where the cucumbers were located in relation to other cucumbers (i.e. if 'barrier' lists two feature types, then this cluster of cucumbers was located in the middle of setup design B shown in Fig. 1 of the main paper; otherwise a single feature is listed). Barrier categories are building, road, garden (community garden with culinary and ornamental plants), lawn (mowed turf, sometimes including small forbs), and forest (urban forest fragment).
- barrier_crossed: Descriptor of what urban landscape feature an insect would have crossed over to transfer dye of the specified 'color rcvd' onto a stigma. Categories are building, road, garden (community garden with culinary and ornamental plants), lawn (mowed turf, sometimes including small forbs), and forest (urban forest fragment).
- color_rcvd: The dye color expected to be received from the cucumbers on the other side of the 'barrier crossed'.
- type: Refers to role of a cucumber cluster in the study: donor = cucumbers are expected to transfer dye to cucumbers on other side of feature, recipient = cucumbers are expected to receive transferred dye from cucumbers on other side of feature, recipient/donor = cucumbers are expected to transfer and receive dye.
- cluster: Categorical number designation according to each color added to cucumber flowers per site and date. All plants in a 'cluster' were placed together and were labeled by the researchers with the same color of dye. Cluster designations are nested within site and date.
- group: Categorical number designation according to which landscape feature separated cucumber clusters per site and date. A group could include two or three clusters (see Fig. 1 in the main paper). Group designations are nested within site and date.
- tot_flwr: Total of male and female flowers an observer could see from their observation spot.
- Bombus: Number of Bombus spp. visits that were not identified to species level.
- B impatiens: Number of Bombus impatiens tallied.
- B gris: Number of Bombus griseocollis tallied.
- Apis: Number of Apis melliferia tallied.
- Megachile: Number of Megachile tallied (not identified to species level).
- Xylo. virginica: Number of Xylocopa virginica tallied.
- Lasioglossum: Number of Lasioglossum tallied (not identified to species level).
- Ceratina: Number of Ceratina tallied (not identified to species level).
- Halictus: Number of Halictus tallied (not identified to species level).
- Augo: Number of Augochlora tallied (not identified to species level).
- Skipper: Number of skippers (Hesperiidae) tallied (not identified to genus/species level).
- fly: Number of flies (Diptera) tallied (not identifies to family level).
- Polistes wasp: Number of Polistes wasps tallied (not identified to species level).
- June bug: Number of June bugs (Cotinis nitida) tallied.
- yellow jacket: Number of yellow jackets (Vespula maculifrons) tallied.
- Toxomerus: Number of hoverflies (Toxomerus spp.) tallied.
- total: Total insect observations.