Interspecific competition reduces seed dispersal in an annual plant and slows simulated range expansions
Data files
Oct 29, 2024 version files 23.56 KB
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McHugh_etal._Interspecific_Comp_Reduces_Disp_2024.zip
18.82 KB
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README.md
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Abstract
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.
For more information, email:
Erin McHugh at e.mchugh@mail.utoronto.ca and/or
Jenn Williams at 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).
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.
Dispersal data
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. Data found in: Competition_Dispersal_2022.csv.
Phenological and trait data
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. Data found in: Competition_Experiment_2022_PhenData.csv.
R Code
Code for fitting negative exponential functions to dispersal data found in 01_fitting_kernels.R.
Code for calculating m and lambda (fecundity) values with and without competition is found in 02_calculating_lambda_and_m_values_final.R.
Code for generating the boxplot showing differences in mean dispersal between competition and no competition treatments for each genotype found in 03_generating_boxplot_meandisp.R.
Code for linear models used in the paper are found in 04_linear_models_updated.R.
Code for making the scatterplot showing maximum dispersal distance as a function of height found in 05_generating_heightvmaxdistance_scatterplot.R.
Code for running the simulations found in 06_simple_sim_one_genotype.R.
Code for analysing the simulation output and making a scatterplot for expansion speed, organized by genotype and m x lambda combination is found in 07_analysing_simulation_results.R.
More details can be found in the README file that accompanies the data.