Data, Metadata, and R script. Williams G. L., and J. S. Brewer. 2024. Naturally diverse plant communities do not resist invasion by the strong competitor, <i>Microstegium vimineum</i>. <i>American Journal of Botany</i> e16362. https://doi.org/10.1002/ajb2.16362

These files contain the metadata, data, and annotated R script used for all analyses with the associated article cited below (Williams and Brewer, 2024).Williams G. L., and J. S. Brewer. 2024. Naturally diverse plant communities do not resist invasion by the strong competitor, <i>Microstegium vimineum</i>. <i>American Journal of Botany</i> e16362. https://doi.org/10.1002/ajb2.16362<br><br>ABSTRACTTheory predicts and empirical studies have shown that ecologically manipulated communities with high species diversity are resistant to invasion, but do these predictions and results hold true when applied to highly competitive invaders in natural communities? Few studies of diversity-mediated invasion resistance have measured both invasion resistance and invader impact in the same study. We used a two-year field experiment to test: 1) diversity-mediated competitive resistance to patch expansion by the grass, <i>Microstegium</i><i> </i><i>vimineum</i>, and 2) the competitive effect of <i>M. </i><i>vimineum</i> on resident plant diversity.<i> </i>We examined responses of <i>M. </i><i>vimineum</i><i> </i>to two native plant density-reduction treatments that had opposite effects on species diversity: 1) reducing species richness via the removal of rare species, and 2) reducing dominance by reducing the density of the dominant resident species. We examined the effects of <i>M. </i><i>vimineum</i> reduction by pre-emergent herbicide on resident diversity in the second year of the study. Neither rare species removal nor dominant species reduction significantly increased <i>M. </i><i>vimineum</i> density (relative growth rate). The pre-emergent herbicide dramatically reduced <i>M. </i><i>vimineum</i> in year 2 of the study, but not most resident plants, which were perennials and indirectly benefited from the herbicide at a more productive site, presumably due to reduced competition from <i>M. </i><i>vimineum</i>. Diversity-mediated resistance did not effectively deter invasion by a highly competitive invader. In the case of <i>M. </i><i>vimineum</i> and at more productive sites, it would appear that nearly complete removal of this invader is necessary to preserve plant species diversity.