DOI: 10.5061/dryad.t80r9c1
title: Data from: Propagule pressure and genetic diversity enhance colonization by a ruderal species: a multi-generation field experiment

description: Colonization is a critical filter, setting the stage for short-term and
 long-term population success. Increased propagule pressure (e.g., more
 founding individuals) usually enhances colonization; however, this pattern
 may be driven by purely numeric effects, population genetic diversity
 effects, or both. To determine the independent and interactive effects of
 propagule pressure and genetic diversity, we conducted a seed addition
 experiment in the field using the ruderal annual Arabidopsis thaliana.
 Propagule pressure treatments spanned five levels, from 32 to 960 seeds
 per 0.25-m2 plot. Founder populations were composed of one, four or eight
 genotypes and exposed to ambient or reduced levels of interspecific
 competition. Genotype monocultures were included to quantify additive
 versus non-additive effects. Populations were followed for three
 generations, with abundance, population persistence and genotype retention
 (the proportion of introduced genotypes persisting over time) as the major
 response variables. Increased propagule pressure enhanced abundance
 immediately following introduction, particularly where nutrient
 availability was high and competition reduced. Greater propagule pressure
 also increased the likelihood of population persistence and genotype
 retention through three generations. However, most populations experienced
 rapid abundance declines over time, yielding no relationship between
 propagule pressure and third-generation abundance across persisting
 populations. Under reduced competition, increased genetic diversity led to
 a marginal increase in persistence through the third generation that was
 more pronounced, and statistically significant, in low nutrient
 conditions. Genetic diversity did not affect persistence through the first
 generation, thus indicating that genetic diversity effects strengthened
 over time. Nevertheless, genotypic mixture populations fell short of
 expectations based on performance in monocultures (negative non-additive
 effects). Increased genetic diversity was also associated with abundance
 declines, largely due to one particularly high-performing genotype in the
 lowest diversity treatments (i.e, genotypic identity effects). Overall,
 our results indicate that increases in both propagule pressure and genetic
 diversity can enhance colonization success but are highly
 context-dependent. They also highlight novel ways in which both factors
 can impact the retention of introduced genetic diversity over time. Our
 findings pinpoint the determinants of a fundamental population process and
 have key implications for applications where enhanced or suppressed
 colonization is desired, including ecological restoration and invasive
 species management.
description: Plot-level treatments
 and performance dataData in both csv files
 were collected in the field during Arabidopsis thaliana's spring
 growing seasons in 2013, 2014 and 2015 (generations 1-3
 post-introduction). The column header abbreviations follow. OBS (plot
 observation number), V1 (plot number), BLOCK (experimental block, 1-9),
 FIELD (general block location, in Western or Eastern field), EXP_MONO
 (indicator of whether plot is in the main experiment [exp] or is a
 monoculture sown for generating expectations in genotypic mixture plots
 [mono/mono2]), COMP (indicator of competition treatment [control/low]),
 SEEDNUM (founder population size treatment, 32/96/160/320/960), GENDIV
 (genetic diversity treatment, 1/4/8), PC1USE (plot-level Axis 1 score from
 soil nutrient PCA), PC2USE (plot-level Axis 2 score from soil nutrient
 PCA), BARECOVER13/14/15 (estimated percent of plot unvegetated in
 generation 1, 2 or 3), PRES13/15 (population presence in generation 1 or
 3), FL_SUM13/14/15 (abundance, the count of reproductive individuals in
 generation 1, 2 or 3), S_13/15 (genotypic richness in generation 1 or 3),
 H_13/15 (genotypic shannon diversity in generation 1 or 3),
 GTYPE_1/2/3/4/5/6/7/8 (genotypic identity of all accessions added to plots
 at experiment initiation).KPC15data_EcolMono.csvPer-genotype abundance dataPer-genotype abundances from plots in the main experiment in year 1 (ABUND_13) and year 3 (ABUND_15) post-introduction. Abundance in genotypic mixture plots were estimated based on observed plot-level abundances and per-genotype relative abundance (based on a subset of samples that were genotyped for a set of accession-specific SNPs).KPC15data_indiv_EcolMono.csvR code for running analysesKPC_AT 2015 analysis_EcolMono.r