Suppression of a plant hormone gibberellin reduces growth of invasive plants more than native plants

Subsequent to escape from intense herbivory in the native range, invasive plants are expected to reduce allocation to costly anti-herbivory defences and have greater competitive ability than co-occurring native species. Given that invasive alien plants often occur in open habitats where light is less limited, it is reasonable to hypothesize that invasive plants should express high concentrations of gibberellins that enable them to allocate more biomass to roots, and thus have higher competitive ability than native plants. To test this prediction, we grew five congeneric pairs of invasive alien plants and native plants under two levels of nutrient availability (low versus high) and treated a half of the plants with a gibberellin biosynthesis inhibitor, paclobutrazol. Paclobutrazol significantly decreased aboveground, belowground, and total biomass of the test plants. Interestingly, the effects on belowground biomass were significantly stronger for invasive plants than for native plants. ...