How plants invade

Invasive plants are responsible for widespread loss of biodiversity, compromised agricultural productivity and sometimes even negative health effects. Understanding the mechanisms that enable invasive plants to become so successful in their new ranges will have long-reaching, worldwide benefits.

The EU-funded TRANSRESSOLID (Transcontinental research on a highly invasive plant species Solidago gigantea - Ecology and evolution in the native and introduced ranges) initiative studied S. gigantea (giant goldenrod), a North American plant, to better understand how it has been such a successful invader in Europe.

Researchers investigated how invasive and native populations of the plant influence species richness and diversity in natural habitats in Europe and America. In controlled greenhouses and common gardens, they tested differences between invasive and native populations in competitiveness, herbivory tolerance, soil biota and genetics. They evaluated different control methods to fight the invading species in Europe.

TRANSRESSOLID found that S. gigantea significantly decreased species richness in Europe, while no such effect was found in North America. In the greenhouse, invasive and native populations did not differ in their competitive ability, but significant differences were found between populations from different elevations.

European plants had a higher herbivory tolerance and mycorrhizal activity than North American plants. European plants also grew bigger in Europe; however, they were not bigger than their North American counterparts when grown in North America.

Researchers also found that short-term control of S. gigantea populations mainly affects fitness and viability of the invader, while long-term control has stronger structural effects by increasing species diversity. Lastly, researchers showed that chemicals in the S. gigantean roots supressed germination of some co-occurring European species.

TRANSRESSOLID findings will help researchers understand how invasive plants like S. gigantea can invade so successfully. The research will have a significant impact on nature conservation and agriculture globally.