Return of diversity: wetland plant community recovery following purple loosestrife biocontrol

Spread of non-native species can be important drivers of widespread biodiversity declines, which often leads to precautionary management based on assumptions that (1) introduced biota have negative impacts and are therefore “guilty” of causing harm, and (2) reducing an introduced species’ abundance will reduce these negative impacts, in turn, benefiting native species. However, we frequently lack data to gauge both the negative impacts of introduced species and the success or failure of chosen management interventions. Addressing these knowledge gaps is critical to improving management outcomes for native species while maintaining public trust to sustain funding of management activities. Here, we investigated the response of Lythrum salicaria (purple loosestrife) and associated plant communities to the implementation of biological control in more than 10 wetland sites in New York State for up to 28 years. Introduced to North America from Europe in the 1800s, L. salicaria is a prime..., Data collection methods are described in the main text of our associated manuscript. They were entered and formatted in Excel, as well as using RStudio., , # Return of diversity: Wetland plant community recovery following purple loosestrife biocontrol

[https://doi.org/10.5061/dryad.z8w9ghxmk](https://doi.org/10.5061/dryad.z8w9ghxmk)

Here, we investigated the response of *Lythrum salicaria* (purple loosestrife) and associated plant communities to the implementation of biological control in more than 10 wetland sites in New York State for up to 28 years. We initially visited 33 sites annually in early September to record *L. salicaria* stem density and cover (%). We also recorded presence and estimated cover (%) for all co-occurring plant species in each quadrat in 16 cover categories (midpoints: 0.01, 0.5, 1, 3, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, and 100%) at all Hudson River Valley, Eastern Lake Ontario and Western New York sites (n=14) in all years and at Montezuma sites (n=19) in 2019 only. The same individual (VN) recorded all vegetation data at all sites and years. Depending on insect releases, we repeated data collection for...,