DOI: 10.5061/dryad.m0cfxppft
title: Data from: Both costs and benefits determine the removal of <em>Datura</em> (Solanaceae) seeds by seed-dispersing ants

description: Mutualisms have both benefits and costs that organisms receive or pay when
 participating in the interaction. However, costs have been largely ignored
 when considering how mutualisms function and evolve. Plants that are
 dispersed by ants produce seeds with attached nutrient-rich food bodies
 (elaiosomes). When ants approach a diaspore (seed with attached
 elaiosome), they are likely to use multiple traits to decide whether or
 not to move it, assessing both the benefits (elaiosome mass) and costs
 (mass of the inedible seed) of doing so. We hypothesized that both the
 mass of the often-inedible seed and the elaiosome mass would affect
 diaspore removal rate. To test this hypothesis, we manipulated the
 elaiosomes of Datura wrightii and D. discolor (Solanaceae). These species
 produce similarly sized elaiosomes (~0.4 mg), but D. wrightii’s seeds (~16
 mg) are twice the mass of D. discolor’s. To measure how variable benefits
 of diaspores would influence seed removal, we offered ants seed that had
 been subjected to one three treatments: seeds with no elaiosome, seeds
 with an unmanipulated elaiosome, and seeds with an experimentally enlarged
 elaiosome (two elaiosomes combined). We then measured the removal rates of
 diaspores by Novomessor cockerelli, a common seed-dispersing ant species
 in Datura’s native habitat. To measure how species differences in the
 costs of diaspores would affect seed removal by ants, another set of
 trials compared removal rates of diaspores when ants were presented with
 unmanipulated seeds of both species simultaneously. Consistent with our
 hypotheses, ants removed seeds with heavier elaiosomes (larger rewards)
 and lighter seeds (lower costs) more quickly. This study, for the first
 time, quantifies a cost of seed dispersal to ants. It highlights the ways
 in which costs, and not benefits alone, can have an impact upon when and
 how organisms participate in mutualisms.
description: # Data from: Both costs and benefits determine the removal of *Datura*
 (Solanaceae) seeds by seed-dispersing ants Dataset DOI:
 [10.5061/dryad.m0cfxppft](10.5061/dryad.m0cfxppft) ## Description of the
 data and file structure These files contain the measurements of elaiosome
 and seed mass for two species of *Datura*, and data from experiments to
 determine how manipulating those masses influences the removal of seeds by
 ants. ### Files and variables bothspeciesdiaspores.csv, this file contains
 all the information regarding the masses of elaiosomes and seeds for both
 species of *Datura* used in this project * Plant.id * The identification
 number given to each plant * Fruit.id * The letter given to each fruit to
 identify it * Seed.id * The number given to each of the ten seeds taken
 from each fruit * Each.fruit * A name to identify each fruit that includes
 the plant identification number * Seed.mass * The mass of each seed in mg
 * Elai.mass * The mass of each elaiosome in mg * Species * The species of
 diaspore * w is *Datura wrightii* * d is *Datura discolor*
 anttimetrials.csv, this file contains the data for the diaspore removal
 speed measurements looking at how diaspore mass affects the speed at which
 it is moved back to the nest by ants * seed.num * the identification
 number of each used in this series * time * the amount of time required
 for the ant to move the seed back to the nest, measured in seconds *
 distance * the distance traveled by the ant back to the nest * all
 distances were constant at 20 cm * rate * the speed at which seeds were
 moved by ants back to the nest * calculated by dividing the distance
 travelled by the time required * the units are centimeters per second *
 mass * the mass in grams of each diaspore discolortreatmentcheck.csv, this
 file contains the data from control trials conducted to see if elaiosome
 removal and replacement influences removal by ants for *D. discolor* *
 trialset * the trial number for each trial set * three trials were
 conducted at each colony * colony * the identification number for each
 colony * five colonies were used in this experiment * trt * the treatment
 for each diaspore * n is “normal” or unmanipulated * r is the diaspores
 that had their elaiosomes removed and replaced * time * the time during
 the trial that the number of diaspores remaining was recorded * seed
 number was recorded every five minutes over the course of 30 minutes * 0
 is the very beginning of the trial * seed.num * the number of seeds
 remaining at each time step wrightiitreatmentcheck.csv, this file contains
 the data from control trials conducted to see if elaiosome removal and
 replacement influences removal by ants for *D. wrightii* * trialset * the
 trial number for each trial set * three trials were conducted at each
 colony * colony * the identification number for each colony * five
 colonies were used in this experiment * trt * the treatment for each
 diaspore * n is “normal” or unmanipulated * r is the diaspores that had
 their elaiosomes removed and replaced * time * the time during the trial
 that the number of diaspores remaining was recorded * seed number was
 recorded every five minutes over the course of 30 minutes * 0 is the very
 beginning of the trial * seed.num * the number of seeds remaining at each
 time step antseedDiscolorraw.csv, this file contains the data from control
 trials conducted to see if varying elaiosome mass influences removal by
 ants for *D. discolor* * trialset * the trial number for each trial set *
 three trials were conducted at each colony * colony * the identification
 number for each colony * five colonies were used in this experiment * trt
 * the treatment for each diaspore * “n” is no elaiosome * “r” is
 unmanipulated diaspore with a “small elaiosome” treatment * “e” is an
 enlarged elaiosome for the “large elaiosome” treatment * time * the time
 during the trial that the number of diaspores remaining was recorded *
 seed number was recorded every five minutes over the course of 30 minutes
 * 0 is the very beginning of the trial * seed.num * the number of seeds
 remaining at each time step antseedraw.csv, this file contains the data
 from control trials conducted to see if varying elaiosome mass influences
 removal by ants for *D. wrightii* * trialset * the trial number for each
 trial set * three trials were conducted at each colony * colony * the
 identification number for each colony * five colonies were used in this
 experiment * trt * the treatment for each diaspore * “n” is no elaiosome *
 “r” is unmanipulated diaspore with a “small elaiosome” treatment * “e” is
 an enlarged elaiosome for the “large elaiosome” treatment * time * the
 time during the trial that the number of diaspores remaining was recorded
 * seed number was recorded every five minutes over the course of 30
 minutes * 0 is the very beginning of the trial * seed.num * the number of
 seeds remaining at each time step specieschoiceraw.csv, this file contains
 the data from control trials conducted to see if seed mass influences
 removal of seeds by ants. * trialset * the trial number for each trial set
 * two trials were conducted at each colony * colony * the identification
 number for each colony * three colonies were used in this experiment * trt
 * the species of each diaspore * w is *Datura wrightii* * d is *Datura
 discolor* * time * the time during the trial that the number of diaspores
 remaining was recorded * seed number was recorded every five minutes over
 the course of 30 minutes * 0 is the very beginning of the trial * seed.num
 * the number of seeds remaining at each time step