PS 41-26 - Investigating the impacts and mechanisms of Vinca minor invasion

Background/Question/Methods

Invasive species are a major driver of ecological change worldwide and understanding the underlying mechanisms of invasion is critical to preventing and managing invasions. Vinca minor is an understudied invasive plant in North American urban forests. The ecological impacts of V. minor and the mechanisms which make it such a successful invader are largely unknown. We conducted three studies to assess the impacts and mechanisms of V. minor invasion. First, we conducted a field survey to determine whether V. minor impacts native plant communities. We surveyed plant communities in invaded and uninvaded areas across urban forests in northern Ontario. Second, we conducted a growth chamber experiment to test for potential allelopathic effects of V. minor foliage. We grew lettuce plants watered with leachate from V. minor foliage or DI water. Finally, we conducted a greenhouse experiment to test for soil biotic legacies of V. minor, where V. minor may alter soil microbial communities in a way that benefits its own growth, for example by promoting mycorrhizal mutualists. We grew V. minor in soils inoculated with either invaded or uninvaded soil from four urban sites and a control with only sterile soil.

Results/Conclusions

In the field survey, we found that V. minor cover was associated with reduced plant species richness and diversity, as well as reduced abundance of sugar maple. Interestingly, sugar maple seedlings growing inside V. minor invasions had higher abundance of arbuscules from arbuscular mycorrhizal fungi in their roots. These results suggest that V. minor may have negative impacts on native plant communities, so we aimed to investigate potential mechanisms. In the allelopathy experiment, we found that lettuce watered with leachate from V. minor foliage performed better than the controls with DI water, suggesting that the potential impacts of V. minor on native plants is unlikely to be due to allelopathic effects of foliage. In the final experiment, we found that V. minor grew better in live field soil than sterilized soil suggesting that it benefits from microbes in the soil, likely arbuscular mycorrhizal fungi. However, no differences were observed between invaded and uninvaded soils suggesting that V. minor does not create a self-promoting soil biotic legacy. Research should continue to investigate other potential mechanisms of V. minor invasion.