DOI: 10.5061/dryad.ffbg79d5b
title: Phenology and flower species availability define wild bee communities on river embankments

description: River embankments cover extensive areas in estuaries worldwide, yet their
 potential for pollinator conservation remains largely unexplored. Even
 more so than road verges, these embankments may offer widespread habitat
 for pollinators due to their size and sun-facing warm slopes. Here we
 present a comprehensive analysis of bee communities from 157 dike
 grasslands along the lower branches of the Meuse and Rhine rivers in the
 Netherlands in relation to vegetation composition and landscape
 characteristics. We encountered nearly half (156) of all Dutch bee
 species. Almost 10% of all individuals belonged to red-listed species,
 especially in early spring when we observed rich ground nesting bee
 communities with their associated kleptoparasites. Wild bee abundance and
 diversity increased with more flowering plant species present, but
 saturated at low flower species richness. This early saturation suggests
 that even modest conservation efforts could effectively alleviate floral
 resource limitation for pollinators. In contrast to the overall pattern,
 red-listed species occurrence increased with flower diversity without
 saturating effects and correlated stronger with landscape level factors.
 Together, these results highlight the unique conservational value of river
 embankments for wild bees and illustrate the unused potential at many dike
 grasslands worldwide.
description: # Phenology and flower species availability define wild bee communities on
 river embankments Dataset DOI:
 [10.5061/dryad.ffbg79d5b](10.5061/dryad.ffbg79d5b) ## Description of the
 data and file structure ### Files and variables #### File:
 LocationCoordinates.csv **Description:** This file holds all location
 codes and their respective RD new (EPSG:28992) coordinates. #####
 Variables * Location: code for the location * x-coord: x coordinate of the
 location (EPSG:28992 - Amersfoort / RD new) * y-coord: y coordinate of the
 location (EPSG:28992 - Amersfoort / RD new) #### File:
 BeesOnDykesNetherlands.csv **Description:** This file holds wild bee
 survey data and associated variables. ##### Variables * Location: code for
 the location used (the coordinates are provided in the
 LocationCoordinates.csv) - Year: the year the survey was taken * Date: the
 date of the survey (DD/MM/YYYY) - Species: the scientific species name *
 Time.start: start time of the survey - in some occasions start time was
 not noted, and N/A was recorded in the data file. All surveys were always
 performed between 9 AM and 5 PM. * Taxon: the taxon the specimen belonged
 to * SamplingEffort(mins): minutes spend surveying the location (Minutes)
 * Observer: person that collected the data * UniqueIdentifier: Identifier
 based on the location + date per location * StatusRl: TRUE or N/A - TRUE
 means species is on the national Dutch red list for wild bees *
 Genus: genus the species belongs to * SpeciesName: the species name. N/A
 when no bee observations during survey * FlowerSpeciesRichness: number of
 flowering species present at time of the survey (#Flower Species on Dyke).
 N/A for few surveys of Ivo where data on flowers was not recorded. *
 FlowerAbundance: Flower abundance. N/A for few surveys of Ivo where data
 on flowers was not recorded.\ IMPORTANT: observers used different,
 incomparable methods to scale flower abundance. Linde used the Tansley
 index (here sum of all scores is given), Ivo counted number of floral
 units along the transect (sum of all FU is given) and Constant counted
 flowering plants in a 5x5m square (sum of all flowering plants is given). 
 * JulianDate: Sampling date translated to Julian date (1 for the 1st of
 Januari - 365 for the 31st of December). * AgricultureArea250m: Area of
 agriculture (excluding flowering crops) in a 250m radius of the location
 as extracted from the TOP10NL shapefile. (Area given in square meters) *
 GrasslandArea250m: Area of non agricultural (semi-natural) grassland in a
 250m radius of the location as extracted from the TOP10NL shapefile. (Area
 given in square meters) * ForrestArea250m: Area of forest in a 250m radius
 of the location as extracted from the TOP10NL shapefile. (Area given in
 square meters) * FruitcropArea250m: Area of flowering crop agriculture
 (e.g. rapeseed, orchards) in a 250m radius of the location as extracted
 from the TOP10NL shapefile. (Area given in square meters) *
 RestArea250m: Area of other elements that bees were not expected to use
 (e.g. open road, water) in a 250m radius of the location as extracted from
 the TOP10NL shapefile. (Area given in square meters) * AreaNNN250m: Area
 of nature reserve in a 250m radius of the location as extracted from the
 TOP10NL shapefile. (Area given in square meters) *The next 6 columns give
 the same information as above but for a 1km radius ([Name]Area1km)* *
 DistanceToNNN: shortest distance from the location to a nature reserve *
 BeeAbundanceNotCorrected: absolute number of individuals counted during
 the transect, not corrected for sampling effort (#individuals/survey) *
 BeeAbundance: Number of individuals counted after correction for sampling
 effort (#individuals/survey/15mins) * Windspeed: highest windspeed
 measured during the sampling day as interpolated from the KNMI database
 (km/h - also see methods section of DOI 10.1098/rspb.2025.0734) *
 Sunshine: percentage of sunshine hours at the sampling day to the total
 day length as interpolated from the KNMI database (% - also see methods
 section of DOI 10.1098/rspb.2025.0734) * Rain: mm of rain (including
 night) at the sampling day as interpolated from the KNMI database (see
 methods section) #### File: FlowerCS.csv **Description:** This file holds
 the full flower surveys collected by Constant connected to the
 BeesOnDykesNetherlands.csv data file. Constant counted all flowering plant
 per species within a quadrant. * Location: code for the location used (the
 coordinates are provided in the LocationCoordinates.csv) * Date: date of
 sampling (DD/MM/YYYY) * Species: plant species * Quantity: number of
 flowering plants counted * survey size (m2): the size of the quadrant in
 which flowering plants were counted (square meters) #### File:
 FlowerIR.csv **Description:** This file holds the full flower surveys
 collected by Ivo connected to the BeesOnDykesNetherlands.csv data file.
 Ivo counted all floral units per flower species along the transect. *
 Location: code for the location used (the coordinates are provided in the
 LocationCoordinates.csv) * Date: date of sampling (DD/MM/YYYY) * Species:
 plant species * Number Floral Units: number of floral units counted ####
 File: FlowerLS.csv **Description:** This file holds the full flower
 surveys collected by Linde connected to the BeesOnDykesNetherlands.csv
 data file. Linde scored flower abundance per species along the transect
 following the Tansley scale. * Location: code for the location used (the
 coordinates are provided in the LocationCoordinates.csv) * Date: date of
 sampling (DD/MM/YYYY) * Transect: Linde estimated Tansley Scale along
 three 50m transects. The number here gives the transect number at the
 location. When determining total Tansley score given in the
 BeesOnDykesNetherlands.csv file Tansley score was first averaged over the
 three transects. * Species: plant species * Tansley scale: flower
 abundance score on the Tansley scale #### **File:
 R\_markup\_Bees\_Dykes\_Netherlands.Rmd** **Description:** this file gives
 the R code used in the analysis and figure creation of DOI
 10.1098/rspb.2025.0734. Subheadings within the code indicate what certain
 parts of the code are used for. The code was originally written and run in
 R version 4.2.2. To use the code one should download the
 BeesOnDykesNetherlands.csv (the other files are supporting information)
 and indicate directory themselves.