Roots of invasive woody plants produce more diverse flavonoids than non-invasive taxa, a global analysis

Invasive plants, particularly woody ones, cause significant ecological and economic losses. However, many factors that underlie the plant invasion process are not well known. There is evidence that some plant traits can be indicators of the degree of invasiveness in woody plants. However, root characters, such as the quantity and diversity of secondary metabolites, have been poorly studied. Flavonoids are widely distributed metabolites in plants and are involved in important biological interactions that take place in the soil. They have been related to increases in defense against pathogens, communication with mutualistic organisms, particularly with arbuscular mycorrhizal fungi and nitrogen fixing bacteria, and with allelopathic effects on neighboring plants. If flavonoids are costly to produce and/or implicated in novel interactions established by successful woody invaders, we could expect invasive species to produce unique flavonoids compared to non-invasive ones. We assessed the literature to evaluate whether the production of flavonoids in roots vary among woody invasive and non-invasive species. Specifically, we tested the effect of invasive status on flavonoid richness, composition, and abundance in roots. We also assessed for indicator flavonoids whose presence and abundance reflect the invasive status. Invasive woody species had higher flavonoid richness in roots than non-invasive, particularly within the chemical subgroups flavonols and flavones. Our results suggest that root flavonoids play an important role in determining the invasion success of woody plants.