DOI: 10.5061/dryad.5tb2rbp3g
title: Species redistribution combined with invasive dominance but not species turnover promotes biotic homogenization following invasion

description: Disentangling the processes lead to biotic homogenization is important and
 will guide conservation efforts. Temporal turnover in species composition
 (i.e., β-diversity) and changes in local α-diversity are two distinct
 processes drive biotic homogenization, but these effects may be masked by
 invasive dominance. After removing invasive dominance, we compared the
 changes in species diversity and species distribution patterns before and
 after invasion aims to measure the relative contribution of species
 turnover and local diversity changes to biological homogenization.
 Invasive dominance indeed had an important contribution to biotic
 homogenization, and the effects increased with an increase in the invasive
 species number. Species composition of native plots was not significantly
 different from invaded plots when removing invasive species. Invasion
 changed native species distribution patterns and promoted the wide spread
 of most species, which causes an increase in local richness and community
 evenness. We highlight that species redistribution combined with invasive
 dominance but not species turnover promotes biotic homogenization,
 especially at early invasion stages. Avoiding the ecological impacts of
 biotic homogenization following invasion will require much stronger
 proactive management to prevent invasive dominance as well as increase
 monitoring at the early stages of invasion.
description: <b>(a) Data
 sources</b> This dataset was
 obtained from 300 5 × 5 m plots in the Brazilian Cerrado [22]. The main
 habitat types are the shrub-dominated habitat (campo sujo) and
 grass-dominated habitat (campo úmido); both types are progressively
 colonized by invasive species. In total, 114 plots were sampled in the
 campo sujo habitat, and 186 plots were sampled in the campo úmido
 habitat. In each plot, a
 systematic survey was conducted to detect all grass layer species
 (incidence data). Eighty plant taxa that belong to 17 botanical families,
 including 76 native species and 4 invasive species, were recorded. The
 invasive species included one pine (<i>Pinus</i> spp.) and
 three African grasses: <i>Urochloa decumbens</i>,
 <i>Melinis repens</i> and <i>Melinis
 minutiflora</i> [23]. The number of invasive species per plot varied
 from 0 (native species only) to 4 (4 invasive species) and represented an
 invasion-intensive gradient. <strong>(b) Data
 analysis</strong> Biotic
 homogenization is quantified as taxonomic homogenization [7] based on the
 pairwise species dissimilarity (Jaccard dissimilarity) between invade
 plots using species presence or absence [3]. Species turnover is computed
 as the change in the pairwise species dissimilarity between native and
 invade plots using species presence or absence (Jaccard dissimilarity).
 Local diversity is measured using species richness (species number in each
 plot) and species evenness (Shannon index). Total invasive effects can be
 quantified by the change in local diversity or species composition before
 and after invasion. The dominance effects of invasive species can be
 quantified by estimating the difference among only native species and
 contrasting with invasive communities where invaders are moved. Species
 turnover can be further assessed by partitioning β-diversity into the two
 processes of species replacement and species loss
 [24]. Species distribution
 pattern changes were evaluated via the relative consistency of the loss or
 addition of individual species before and after invasion [25]. We
 calculated the proportion of plots, where each species was a new colonist,
 and the proportion of loss of species in invaded plots, and related these
 species frequencies to the native plots. The stable distribution of
 species before and after invasion displayed a line with a slope of 1
 (X=Y), that is, its distribution range was not changed. Species above the
 X=Y line indicate that they are widespread in their distribution range
 after invasion, while those under the X=Y line indicate a narrowed
 distribution range. We
 performed Kruskal-Wallis tests [26] to compare the differences in local
 diversity and species composition between groups with a different number
 of invasive species (e.g., 0, 1, 2, 3 or 4). Plots with three or four
 invasive species were grouped in each habitat due to their smaller
 numbers. All analyses were implemented using R
 [27].