These data were collected by Carla J. Essenberg, who can be contacted with questions. Until July 2015, she will be at the Center for Insect Science at the University of Arizona. Fuller descriptions of data collection methods are contained in the following two articles: Essenberg, C. J. 2012. Scale-dependent shifts in the species composition of flower visitors with changing floral density. Oecologia. DOI: 10.1007/s00442-012-2391-z. Essenberg, C. J. Accepted. Explaining the effects of floral density on flower visitor species composition. American Naturalist. ##################################################################### FILE: Visitation.csv OVERVIEW: Per-flowerhead visitation rates to Holocarpha virgata ssp. virgata (Asteraceae) and densities of flower-visiting insects in 2 x 2 m plots spanning the available range of floral densities at a variety of sites and dates within the flowering season DATA CONTAINED IN EACH COLUMN: Site: One- or two-letter code for each site Obs: Unique code for each observation period (consisting of two days of observation, usually consecutive) at each site. This unique code consists of the site code followed by an underscore followed by a number (1 for the first observation period at that site, 2 for the second, 3 for the third) Plot: Within each site, each plot receives a unique code PlotFlDen: Average floral density within the plot, in flowerheads/m^2 (all flowers in plots belonged to H. virgata) MdiskDen: Average floral density within the plot, in male-phase florets/m^2 MelVis: Average flower visitation rate by the long-horned bee Melissodes lupina, in visits/flowerhead/hour HalVis: Average flower visitation rate by the sweat bees Halictus ligatus and Lasioglossum titusi, in visits/flowerhead/hour HonVis: Average flower visitation rate by honeybees, Apis mellifera, in visits/flowerhead/hour OtherVis: Average flower visitation rate by all other visitors combined, in visits/flowerhead/hour TotVis: Average flower visitation rate by all visitors combined, in visits/flowerhead/hour MelDen: Average density of the long-horned bee Melissodes lupina, in individuals/m^2. This and the other density values come from 18 instantaneous counts of each plot, distributed over the same periods of time as the visitation observations HalDen: Average density of the sweat bees Halictus ligatus and Lasioglossum titusi, in individuals/m^2 HonDen: Average density of honeybees, Apis mellifera, in individuals/m^2 OtherDen: Average density of all other visitors combined, in individuals/m^2 ##################################################################### FILE: SiteData.csv OVERVIEW: Latitude and longitude of the center point of each site used in Visitation.csv and area occupied by summer-flowering plants within 200m of the center of each site DATA CONTAINED IN EACH COLUMN: Site: Same as in Visitation.csv Latitude: hddd.ddddd°; WGS 84 Longitude: hddd.ddddd°; WGS 84 HVPatchArea: Area occupied by patches of H. virgata, in m^2 TotalPatchArea: Area occupied by patches of all summer-flowering plants, in m^2 ##################################################################### FILE: ObsData.csv OVERVIEW: Dates of each observation recorded in Visitation.csv along with average H. virgata floral densities within H. virgata patches and average densities of floral resources within patches of all summer-flowering species observed within 200m of the center of each site during each observation DATA CONTAINED IN EACH COLUMN: Obs: Same as in Visitation.csv Date1: yyyymmdd, refers to the first of two days of observation Date2: yyyymmdd, refers to the second of two days of observation Day: Days since beginning of study HVFlDen: Average floral density of H. virgata in H. virgata patches within 200m of site center, in male florets/m^2 TotalFlDen_P: Average floral resource density (across all plant species) in patches of summer-flowering plants within 200m of site center, in H. virgata flowerhead equivalents, based on pollen production TotalFlDen_S: Average floral resource density (across all plant species) in patches of summer-flowering plants within 200m of site center, in H. virgata flowerhead equivalents, based on nectar sugar production Diversity: Floral diversity within 200m of site center, as measured by 1 – Simpson’s Index ##################################################################### FILE: Nectar.csv OVERVIEW: Total nectar sugar produced by H. virgata flowerheads in 1 x 1 m plots of varying floral densities at the sites and dates used in Visitation.csv. Flowerheads were bagged in the morning before insects became active and nectar measured in the late morning or early afternoon, after the conclusion of flower visitation observations DATA CONTAINED IN EACH COLUMN: Site: Same as in Visitation.csv Obs: Same as in Visitation.csv Plot: Within each site, each plot receives a unique code PlotFlDen: Floral density within the plot, in flowerheads/m^2 Mdisk: Number of male-phase disk florets on the flowerhead Sugar: Amount of nectar sugar in the flowerhead, in micrograms ##################################################################### FILE: NectarTiming.csv OVERVIEW: Total nectar sugar measured in 11 bagged flowerheads of H. virgata at multiple points throughout a single day, August 22, 2010. Flowerheads were bagged before pollinators became active in the morning. At each measurement point, the flowerhead was emptied of nectar DATA CONTAINED IN EACH COLUMN: Flowerhead: A unique number for each flowerhead Fdisk: Number of female-phase disk florets on the flowerhead Mdisk: Number of male-phase disk florets on the flowerhead Time: Nectar measurement time, mm:ss Sugar: Amount of nectar sugar in the flower, in micrograms ##################################################################### FILE: Pollen.csv OVERVIEW: Pollen produced on one day by H. virgata flowerheads in the 1 x 1 m plots also used for nectar measurements. Flowerheads were collected in the morning before insects became active DATA CONTAINED IN EACH COLUMN: Site: Same as in Visitation.csv Obs: Same as in Visitation.csv Plot: Same as in Nectar.csv PlotFlDen: Floral density within the plot, in flowerheads/m^2 Mdisk: Number of male-phase disk florets on the flowerhead Pollen: Amount of pollen produced by the flowerhead, in thousands of pollen grains ##################################################################### FILE: HandlingTimes.csv OVERVIEW: Flower handling times recorded during the flower visitation observations described above (and reported in Visitation.csv) DATA CONTAINED IN EACH COLUMN: Site: Same as in Visitation.csv Obs: Same as in Visitation.csv Plot: Same as in Visitation.csv Visitor: A unique number for each individual insect Taxon1: mel = Melissodes lupina, hon = Apis mellifera, hal = sweat bee belonging to Halictus ligatus or Lasioglossum titusi Taxon2: Applies to sweat bees only. Hlig = Halictus ligatus, Ltit = Lasioglossum titusi; where neither is specified, the observer was not able to determine the species to which the individual belonged HandlingTime: Flower handling time for a single flowerhead, in seconds ##################################################################### FILE: SearchSpeeds.csv OVERVIEW: Search speeds calculated from flight times and estimated distances between flowerheads, in 2009 (the summer before the rest of the data in this dataset were collected), for the main visitors to H. virgata DATA CONTAINED IN EACH COLUMN: Date: yyyymmdd Visitor: A unique number for each individual insect Taxon: mel = Melissodes lupina, hon = Apis mellifera, hal = sweat bee belonging to Halictus ligatus or Lasioglossum titusi Distance: Distance between flowerheads (that is, the distance from the flowerhead the insect took off from to the flowerhead it next landed on), in centimeters FlightTime: Time required to fly between the two flowerheads, in seconds SearchSpeed: Search speed (distance between flowers/time required to travel between them), in m/s ##################################################################### FILE: BodySize.csv OVERVIEW: Intertegular spans of each of the four most common flower visitors to H. virgata DATA CONTAINED IN EACH COLUMN: Date: Date the specimen was collected, yyyymmdd Voucher: Voucher number for the specimen in the University of California-Riverside Entomology Research Museum Taxon: mel = Melissodes lupina, hon = Apis mellifera, Hlig = Halictus ligatus, Ltit = Lasioglossum titusi Gender: M = male, F = female ITspan: Intertegular span, as defined by Cane 1987, Journal of the Kansas Entomological Society 60:145-147, in millimeters #####################################################################