DOI: 10.5061/dryad.r4xgxd2pt
title: Interspecific competition reduces seed dispersal in an annual plant and slows simulated range expansions

description: Understanding the factors influencing how fast populations can spread
 across the landscape will be crucial as species ranges shift due to
 climate change. While the role of abiotic factors in determining expansion
 speed has been well studied in theory and empirical research, how
 competition impacts speed has received far less attention. Here, we
 investigated how seed dispersal distances change in response to
 competition and how these changes to distributions of dispersed seeds
 impact expansion speed. We dispersed four genotypes of the annual plant
 Arabidopsis thaliana with variation in life history traits into greenhouse
 mesocosms of either empty habitat or habitat containing the annual grass
 competitor, Lolium multiflorum. We found that competition decreased both
 mean and maximum dispersal distance. We then built a simulation model of
 range expansion with experimental data from this and a prior experiment to
 explore whether competition slows species expansions primarily through
 decreasing dispersal or fecundity. We found that competition primarily
 slows expansion speed through decreases in dispersal, but that when
 competition impacts both dispersal and fecundity, expansions slow more
 than with dispersal alone. The genotype with traits associated with longer
 distance dispersal was the most affected by competition in both
 experimental dispersal and simulations. This research suggests that not
 only does competition slow range expansions through decreases in both
 fecundity and dispersal, but that there may be consequences for
 evolutionary processes at the leading edge.
description: <strong>Dispersal data</strong>
 Data containing the number of seedlings in dispersal mesocosms
 for each replicate. Seedlings were counted by dividing each of the five
 8x8-cm pots into eight 1-cm bins and counting the number of seedlings in
 each bin. The 0 cm bin corresponds to the seedlings in the pot containing
 the parent plant (the plant whose seeds were dispersing), and centimetres
 1-40 correspond to each 1 cm bin in the dispersal mesocosm.<strong>
 Data found in: Competition_Dispersal_2022.csv.</strong>
 <strong>Phenological and trait
 data</strong> Data containing the germination
 date, date of bolting, date of first flower, date of first mature silique,
 etc., as well as height and silique (fruit) number (measured on the day
 that mesocosms were dismantled) for each replicate in the dispersal
 experiment. Additionally, data includes the day that replicates were
 planted, how long they spent cold-stratifying, when they went into
 dispersal mesocosms, and when they came out of dispersal mesocosms.
 <strong>Data found in:
 Competition_Experiment_2022_PhenData.csv.</strong>
 <strong>R Code</strong> Code for
 fitting negative exponential functions to dispersal data found in
 <strong>01_fitting_kernels.R</strong>. Code
 for calculating m and lambda (fecundity) values with and without
 competition is found in
 <strong>02_calculating_lambda_and_m_values_final.R</strong>. Code for generating the boxplot showing differences in mean dispersal between competition and no competition treatments for each genotype found in <strong>03_generating_boxplot_meandisp.R</strong>. Code for linear models used in the paper are found in <strong>04_linear_models_updated.R</strong>. Code for making the scatterplot showing maximum dispersal distance as a function of height found in <strong>05_generating_heightvmaxdistance_scatterplot.R</strong>. Code for running the simulations found in <strong>06_simple_sim_one_genotype.R</strong>. Code for analysing the simulation output and making a scatterplot for expansion speed, organized by genotype and m x lambda combination is found in <strong>07_analysing_simulation_results.R</strong>. More details can be found in the README file that accompanies the data.
description: # Metadata for: data accompanying McHugh, E.E., Urquhart, C.A., Williams,
 J.L, and Lustenhouwer, N. (2024). “Interspecific competition reduces seed
 dispersal in an annual plant and slows simulated range expansions”. Oikos.
 For more information, email: Erin McHugh at
 [e.mchugh@mail.utoronto.ca](mailto:e.mchugh@mail.utoronto.ca) and/or Jenn
 Williams at
 [jennifer.williams@geog.ubc.ca](mailto:jennifer.williams@geog.ubc.ca) ###
 File 1: Competition\_Dispersal\_2022.csv File contains the number of
 seedlings counted per cm of the dispersal mesocosm for each replicate.
 There were five 8 cm x 8 cm pots. All seedlings in the pot with the parent
 plant were counted and indicated as 0 cm. Seedlings that dispersed past
 the parent pot were counted in 1 cm increments. * RIL: Refers to the
 genotype of the replicate (either 53, 58, 144, or 187). * Rep: Replicate
 number assigned to each replicate of each genotype during initial
 planting. * 0:40: Refers to the cm bin of the dispersal mesocosm. Column
 labelled “0” refers to all the seedlings that fell into the parent pot.
 Columns 1-40 refer to cm away from the parent pot. * treatment: Either
 “LOLIUM” (replicates allowed to disperse into runways with *L.
 multiflorum* plants) or “EMPTY” (replicates allowed to disperse into empty
 habitat. * notes: any notes collected while counting seedlings. *
 datecollected: the day the data was collected, in dd/mm/year. ### File 2:
 Competition\_Experiment\_2022\_PhenData File contains data on the major
 phenological milestones and traits of each replicate. All dates are in
 dd/mm/year format. * RIL: genotype of the replicate. * Habitat: Type of
 habitat the replicate dispersed its seeds into. * Rep: ID assigned to each
 replicate of each genotype during planting. * PlantDate: Day that the
 replicate was planted. * ChillTime: Number of days the replicate spent
 cold stratifying in the fridge. * GermDate: Day that the replicate
 germinated. * BoltDate: First day that the replicate bolted. * RDBolt:
 Rosette diameter at bolting (mm). * FirstFlower: First day that the
 replicate had an open flower. * FirstMatSilique: Day that the replicate
 had its first mature (orange) silique. * IntoRunway: Day that the
 replicate was transferred into a dispersal mesocosm. * RunwayDown: Day
 that the replicate came out of the dispersal mesocosm. * Height: Height of
 replicate in mm. * SiliqueNo: Number of siliques (mature fruits) on each
 plant, counted when the replicates came out of the dispersal mesocosm. *
 TraitDate: Date that SiliqueNo and Height were measured. * SeedMass: Mean
 weight of 100 seeds in grams (taken from Williams, J.L., Kendal, B.E., and
 Levine, J.M. 2016. Data from: Rapid evolution accelerates plant population
 spread in fragmented experimental landscapes. Dryad Digital Repository,
 [https://datadryad.org/stash/dataset/doi:10.5061/dryad.q7605#citations](https://datadryad.org/stash/dataset/doi:10.5061/dryad.q7605#citations)). ### R Files: 01_fitting_kernels.R: code for fitting negative exponential function to dispersal data for each replicate in the dispersal experiment. Calls in raw dispersal data found in Competition_Dispersal_2022.csv. 02_calculating_lambda_and_m_values_final.R: code to calculate m and lambda values with and without competition for each genotype used in the experiment. Calls in Competition_Dispersal_2022.csv and compexp2022_july2023_wholepot_m_values.csv. 03_generating_boxplot_meandisp.R: code for boxplot (fig. 2) that shows mean dispersal with and without competition for each genotype. Calls in output of calculating_lambda_and_m_values.R. 04_linear_models_updated: code to run linear models used in manuscript. Calls in Competition_Dispersal_2022.csv, Competition_Experiment_2022_PhenData.csv, and the parms_relevelled file written in 03_generating_boxplot_meandisp.R. 05_generating_heightvmaxdistance_scatterplot.R: code for scatterplot (fig. 3) showing maximum dispersal distance as a function of plant height. Calls in Competition_Dispersal_2022.csv and Competition_Experiment_2022_PhenData.csv. 06_simple_sim_one_genotype.R: script for expansion simulation, adapted from Urquhart & Williams (2021) and Williams, Snyder, and Levine (2016). Calls in values calculated in calculating_lambda_and_m_values.R. 07_analysing_simulation_results.R: summarizing simulation results for each genotype x fecundity x m combination, then combining into one master sheet to make figure 4, which shows invasion speed and cv of invasion speed for each genotype x fecundity x m combination. Calls in files in the simulation_results folder. Data can also be found in [https://github.com/mchughee/InvasionSpeedCompSupplement2023](https://github.com/mchughee/InvasionSpeedCompSupplement2023).