DOI: 10.5061/dryad.4k7d5n7
title: Data from: Direct effects of a non-native invader erode native plant fitness in the forest understory

description: 1. The direct role of non-native plant invaders in driving negative
 population- and community-level processes of native species has been
 recently questioned. Addressing this controversy requires determining
 quantitatively if invaders negatively affect native population fitness.
 Because the invasion of non-natives often coincides with other
 anthropogenic stressors, experiments that partition the putative impact of
 non-natives from other known stressors and assess their potential
 synergies are required. While many studies have examined the effects of
 non-natives on components of native plant performance, studies that
 decompose the net fitness effects of non-natives from other anthropogenic
 stressors on population growth rate are lacking. 2. We used six years of
 detailed demographic data to parameterize a size-dependent integral
 projection model to examine the individual and combined effects of an
 allelochemical-producing invader (Alliaria petiolata) and an overabundant
 ungulate herbivore (Odocoileus virginianus) on the population dynamics of
 an understory perennial (Trillium erectum). 3. We show that Alliaria
 consistently and negatively affects the population dynamics of Trillium.
 Specifically, this invader reduces native population growth rate and
 alters the size distribution of the population at equilibrium. Alliaria
 also works in concert with the known negative impacts of overabundant
 white-tailed deer, illustrating the additive effects of anthropogenic
 stressors on native plant dynamics. 4. Synthesis. Alliaria’s effects on
 vital rates differed in magnitude and sign across the native’s lifecycle,
 highlighting the importance of detailed demographic analyses. Globally,
 our study provides novel empirical support for the claim that non-native
 invasive species can significantly and directly reduce the fitness of
 native plants.
description: P.array20102010-2011 demographic parameter coefficients for Trillium for four treatments (see metafile).GM_RanPermut_P.array2010.RdaP.array20112011-2012 demographic parameter coefficients for Trillium for four treatments (see metafile)GM_RanPermut_P.array2011.RdaP.array20122012-2013 demographic parameter coefficients for Trillium for four treatments (see metafile).GM_RanPermut_P.array2012.RdaP.array20132013-2014 demographic parameter coefficients for Trillium for four treatments (see metafile).GM_RanPermut_P.array2013.RdaP.array20142014-2015 demographic parameter coefficients for Trillium for four treatments (see metafile).GM_RanPermut_P.array2014.RdaP.array20152015-2016 demographic parameter coefficients for Trillium for four treatments (see metafile).GM_RanPermut_P.array2015.RdaMetadata html fileThis is a metadata html file that was composed using R Markdown and executes R code. The required demographic parameter estimates can be uploaded from the associated Rda files associated with this archived Dryad Digital Repository http://doi:10.5061/dryad.4k7d5n7 (Bialic-Murphy et al. 2019). This file uses parameter coefficients calculated in a separate R script (not provided in our supplement) and builds annual integral projection models from 2010-2016 for four treatments: A) deer access and garlic mustard ambient, B) deer access and garlic mustard weeded, C) deer exclusion and garlic mustard ambient, and D) deer exclusion and garlic mustard weeded (i.e., removal of both stressors). Using the component matrices of the discretized kernel matrix (K=P+F), this script generates the annual population growth rates, the cumulative growth rates from 2010 to 2016 (λc), and the time-averaged geometric mean growth rate, which captures the time-averaged population growth rate over a single transition year (λper year = sixth root of λc).Bialic-Murphy_2019_JoE_Metadata.html