DOI: 10.5061/dryad.4b8gthtnd
title: Spatial patterns of seed removal by harvester ants in a seed tray experiment

description: Using a selection of native grass and forb seeds commonly seeded in local
 restoration projects, we conducted a field experiment to evaluate the
 effects of seed species, distance of seed patches from nests, and distance
 between patches on patterns of seed removal by Owyhee harvester ants,
 Pogonomyrmex salinus (Olsen) (Hymenoptera: Formicidae). To
 provide context for ants’ seed preferences, we evaluated differences in
 handling time among seed species. In addition, we assessed the influences
 of cheatgrass, Bromus tectorum (L.) (Poales: Poaceae),
 and Sandberg bluegrass, Poa secunda (J. Presl) (Poales: Poaceae),
 cover on seed removal. We found significant differences in removal rates
 among seed species. In general, seeds placed closer to nests were more
 vulnerable to predation than those placed farther away, and seeds in
 closely spaced patches were more vulnerable than seeds in widely spaced
 patches. However, the strength of these effects differed by seed species.
 Differences in handling time among seed species may help to explain these
 findings; the protective effect of from-nest distance was weaker for
 species that required less time to transport. For 2 of the seed species,
 there was an interaction between the distance of seed patches from nests
 and the distance between patches such that the protective effect of
 distance between patches decreased as the distance from nests increased.
 Cheatgrass and bluegrass cover both had small protective effects on seeds.
 Taken together, these results offer insight into the spatial ecology of
 harvester ant foraging and may provide context for the successful
 implementation of restoration efforts where harvester ants are present.
description: # Spatial patterns of seed removal by harvester ants in a seed tray
 experiment
 [https://doi.org/10.5061/dryad.4b8gthtnd](https://doi.org/10.5061/dryad.4b8gthtnd) This dataset includes six tabular data files (seedtrayexperimentdata.csv, controlsitedata.csv, seedhandlingdata.csv, collectedforagedata.csv, groundcoverdata.csv, and trunktraildirections.csv) and the associated analysis script (grossklausetalanalysis.R). ## Metadata **Seed tray experiment data (seedtrayexperimentdata.csv)** tray = unique tray identifier in the format: week.colony.tray week = week of experiment; 1-9 colony = unique colony identifier juliandate = Julian date central direction = direction of center point for tray placement; degrees clockwise from N traydirection = direction of individual tray; degrees clockwise from N within_10 = binary variable specifying whether tray is within a 10-degree wedge around nearest trunk trail; 0 = no, 1 = yes within_20 = binary variable specifying whether tray is within a 20-degree wedge around nearest trunk trail; 0 = no, 1 = yes within_30 = binary variable specifying whether tray is within a 30-degree wedge around nearest trunk trail; 0 = no, 1 = yes within_40 = binary variable specifying whether tray is within a 40-degree wedge around nearest trunk trail; 0 = no, 1 = yes within_50 = binary variable specifying whether tray is within a 50-degree wedge around nearest trunk trail; 0 = no, 1 = yes within_60 = binary variable specifying whether tray is within a 60-degree wedge around nearest trunk trail; 0 = no, 1 = yes cheatgrass = extent of cheatgrass cover between tray and focal colony; m bluegrass = extent of bluegrass cover between tray and focal colony; m fromnestdist = distance between focal harvester ant colony and tray; m bin = from-nest distance stratum; 1 = 3.5 to 5.5 m, 2 = 5.6 to 7.6 m, 3 = 7.7 to 10 m btwtraydist = distance between trays; m numtinycol = number of *Pheidole* ant colonies within a 10 m radius of the focal harvester ant colony start = time that seeds were placed in their trays on the morning of seed deployment in the format: hh:mm timesincestart = number of hours since seed deployment wr_remain = number of wildrye seeds remaining at time of observation rg_remain = number of ricegrass seeds remaining at time of observation bg_remain = number of bluegrass seeds remaining at time of observation p_remain = number of penstemon seeds remaining at time of observation gm_remain = number of globe mallow seeds remaining at time of observation wr_available = number of wildrye seeds available as of previous observation (not calculated for excluded observations) rg_available = number of ricegrass seeds available as of previous observation (not calculated for excluded observations) p_available = number of penstemon seeds available as of previous observation (not calculated for excluded observations) gm_available = number of globe mallow seeds available as of previous observation (not calculated for excluded observations) exclude = binary variable specifying observations to exclude from analysis; 0 = include, 1 = exclude notes = notes about the observation **Control site data (controlsitedata.csv)** tray = unique tray identifier in the format: week.site.tray. tray either p (penstemon mix) or g (globe mallow mix) week = week of experiment; 1-9 site = unique control site identifier juliandate = Julian date start = time that seeds were placed in their trays on the morning of seed deployment in the format: hh:mm timesincestart = number of hours since seed deployment wr_remain = number of wildrye seeds remaining at time of observation rg_remain = number of ricegrass seeds remaining at time of observation bg_remain = number of bluegrass seeds remaining at time of observation p_remain = number of penstemon seeds remaining at time of observation gm_remain = number of globe mallow seeds remaining at time of observation tot_lost = total number of seeds lost at time of observation (excluding bluegrass, not calculated for excluded observations) exclude = binary variable specifying observations to exclude from analysis; 0 = include, 1 = exclude notes = notes about the observation **Seed handling data (seedhandlingdata.csv)** species = seed species juliandate = Julian date temp = temperature at time of observation; degrees C traveltime = time taken by ant to travel 200 cm with seed from tray to nest; s travelrate = calculated rate of travel; cm/s securetime = time taken by ant to secure seed in its mandibles; s numseeds = number of seeds carried **Collected forage data (collectedforagedata.csv)** colony = unique colony identifier week = week of experiment; 2-9 juliandate = Julian date foragetype = type of forage item collected by ant count = number of items notes = notes about the observation **Ground cover data (groundcoverdata.csv)** *All columns in this spreadsheet are in the format: category_cover type*. *Values under each column are the percent understory cover of the cover type within the category (10 replicates per category).* categories: exoticmustards (exotic mustards), bluegrass (Sandberg bluegrass), fescue (sixweeks fescue), cheatgrass (cheatgrass), debrisbareground (debris and bare ground), and mixedgrasses (mixed grasses) cover types: bluegrass (Sandberg bluegrass), fescue (sixweeks fescue), cheatgrass (cheatgrass), mustards (exotic mustards), debrisbareground (debris and bare ground) **Trunk trail directions (trunktraildirections.csv)** *This data was used to calculate the columns within_10, within_20, within_30, within_40, within_50, and within_60 in the seedtrayexperimentdata.csv spreadsheet.* colony = unique colony identifier week = week of experiment; 1-9 direction_1 = direction of trunk trail; degrees clockwise from N direction_2 = direction of trunk trail; degrees clockwise from N direction_3 = direction of trunk trail; degrees clockwise from N direction_4 = direction of trunk trail; degrees clockwise from N direction_5 = direction of trunk trail; degrees clockwise from N direction_6 = direction of trunk trail; degrees clockwise from N ## Data analysis **Analysis script: grossklausetalanalysis.R.** *This R script has been annotated for ease of use and navigation.*