Numbers of positive (homogenization) and negative (diversification) values of the homogenization index resulting from pairwise comparisons among 32 cities (left), and variation in values of the homogenization index among the studied habitat types, showing the homogenization (hom) effect of alien species on species composition similarity.

<p>Differences between Jaccard similarities based on all and native species were tested using a paired Wilcoxon test (***, p < 0.001). For explanation of box-and-whisker plots see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071783#pone-0071783-g003" target="_blank">Figure 3</a>.</p>