DOI: 10.5061/dryad.vj260
title: Data from: Frequency dependence and ecological drift shape coexistence of species with similar niches

description: The coexistence of ecologically similar species might be counteracted by
 ecological drift and demographic stochasticity, both of which erode local
 diversity. With niche differentiation, species can be maintained through
 performance trade-offs between environments, but trade-offs are difficult
 to invoke for species with similar ecological niches. Such similar species
 might then go locally extinct due to stochastic ecological drift but there
 is little empirical evidence for such processes. Previous studies have
 relied on biogeographical surveys and inferred process from pattern, while
 experimental field investigation of ecological drift are rare. Mechanisms
 preserving local species diversity, such as frequency-dependence (e. g.
 rare-species advantages), can oppose local ecological drift, but the
 combined effects of ecological drift and such counteracting forces have
 seldom been investigated. Here, we investigate mechanisms between
 coexistence of ecologically similar but strongly sexually differentiated
 damselfly species (Calopteryx virgo and C. splendens). Combining field
 surveys, behavioral observations, experimental manipulations of species
 frequencies and densities, and simulation modelling, we demonstrate that
 species coexistence is shaped by the opposing forces of ecological drift
 and negative frequency-dependence (rare species advantage), generated by
 interference competition. Stochastic and deterministic processes therefore
 jointly shape coexistence. The role of negative frequency-dependence in
 delaying the loss of ecologically similar species, such as those formed by
 sexual selection, should therefore be considered in community assembly,
 macroecology, macroevolution and biogeography.
description: R-script (code) to Fig.
 1A-B and Table A1This file contains the
 R-script and code that can be used to generate Fig. 1A-B and Table A1 in
 the manuscript. These figures show geographic variation in species
 frequencies (Fig. 1A) and density-differences between population
 categories (Fig. 1B), as well as the statistical tests (ANOVA and GLM) for
 comparison of these categories. Data-file associated with this script is
 provided separately.DryadRScriptFig1TableA1.txtGeographic variation in species frequencies and densitiesThis file contains the data behind Fig. 1A-B and Table A1 in the manuscript. These figures show geographic variation in species frequencies (Fig. 1A) and density-differences between population categories (Fig. 1B). The script-file (R-code) associated with this datafile is provided separately, and can be used to reproduce the statistical test associated with Table A1.DryadCalopteryxSpeciesFrequenciesData.txtMale aggression dataset (Fig. 3A-B, Tables A6-A7)This file contains the C. splendens male aggression data in the intruder experiments that were performed in two allopatric and two sympatric populations (Fig. 3A-B, Tables A6-A7).MaleAggressionDataSetDryad.txtScript (R-code) of longevities of C. splendens and C. virgo in the mesocosm experimentsThis file contains the script (R-code) needed to generate Fig. 2 and the statistical tests in Tables A2-A5, as well as the supporting Fig. D1. Three datafiles (in CSV-format) are uploaded separately, and all of these data come from the mesocosm experiments where species densities- and frequencies were experimentally manipulated in outdoor cages.DryadRScriptFig2TablesA2ToA5.txtDatafile "Sympatric" from the mesocosm experiments (Fig. 2A)This datafile contains longevities of the two different species (C. splendens and C. virgo) under three different sympatric frequency-treatments and two density-treatments which are shown in Fig. 2A and Table A2. Together with the script with R-code (provided separately), readers should be able replicate the statistical tests in Table A2.Sympatric.txtDatafile "Splendens" in the mesocosm experiments in Fig. 2B and Table A3This datafile contains longevity information from the mesocosm experiments for the C. splendens males, shown in Fig. 2B and Table A3. Script with R-code is provided separately and should be used with this datafile to re-generate the statistical results in Table A3.Splendens.txtDatafile "Virgo" for the mesocosm experiments on male longevity (Fig. 2C, Tables A4-5)This datafile contains longevity information from the mesocosm experiments for the C. splendens males, shown in Fig. 2C and Table A4-A5. Script with R-code is provided separately and should be used with this datafile to re-generate the statistical results in Table A4-A5.Virgo.txtScript (R-code) for simulating negative frequency-dependence and ecological drift (Fig. 4)This file contains the R-code needed to run the simulations in Fig. 4A-F and associated Supplemental figures. The code can be modified to vary community size (J), the strength of negative frequency-dependence (NF) and fitness ratio (FR). Each simulation run follows only 10 populations to speed up computing power, but the code can easily be modified to follow more populations, as well as the number of generations to follow. For further details, see Material and Methods in our paper and Vellend (2016; see the reference list in the paper). The original code that we have modified in this study can be found here: https://github.com/aammd/ecotheory/blob/master/vignettes/Box2.Rmd [MacDonald & Vellend. R code accompanying Vellend (2016) The Theory of Ecological Communities. Princeton University Press].DryadRCodeFig4DriftSimulations.txt