Does the flavonoid quercetin influence the generalist-selective nature of mycorrhizal interactions in invasive and non-invasive native woody plants?

It has been suggested that invasive plant species are more generalist than non-invasive species in their interactions with arbuscular mycorrhizal fungi (AMF), allowing them to associate with novel AMF communities. There is emerging evidence suggesting that the flavonoid quercetin may play a role in regulating these interactions as a signaling compound. In this study, we experimentally grew three invasive alien and three non-invasive native woody species with AMF communities collected from within (though foreign to invasives) and outside their current distribution ranges. After 96 days, we: (a) assessed mycorrhizal colonization rates; (b) evaluated the impact of these interactions on plant performance (growth and phosphorus nutrition); and (c) tested whether these responses were influenced by the addition of quercetin to the plant growth medium. Our findings reveal that the invasive species exhibited mycorrhizal colonization when grown with both novel AMF communities and benefited from them in terms of phosphorus (P) nutrition. In contrast, two of the three non- invasive native species showed mycorrhizal colonization and enhanced P nutrition only with AMF from their current distribution range, but not with novel AMF from outside their range, suggesting selective behavior in their mycorrhizal interactions. The addition of quercetin did not have a strong effect on mycorrhizal colonization in either invasive or non-invasive native species. However, quercetin promoted moderate increases in P nutrition in the two non-invasive native species when grown with the novel AMF communities. Overall, the results suggest that invasive species are more generalist in their AM symbiosis than two of the three non-invasive species, and that the addition of quercetin had a limited, moderate influence on their AM interactions.