Invasive Plants Show Enhanced Competitive Ability in Non-Native Environments

A recent study has investigated whether invasive plants exhibit superior competitive ability in their introduced ranges compared to their native habitats. The research focused on *Erigeron canadensis*, commonly known as Canadian horseweed, and found that plants originating from non-native populations possessed a 19.2% higher competitive ability than those from native populations. This competitive advantage was observed across both watered and drought conditions during the study.

While drought conditions generally reduced overall competitive ability by 12.9%, the difference in competitive ability between native and non-native populations remained significant, with no substantial change in their relative advantage under drought. Canadian horseweed, native to North and Central America, has spread extensively across Europe, Asia, and other global regions. In these introduced areas, it is known to suppress other plant species, leading to a reduction in local plant diversity.

Researchers conducted a large glasshouse experiment, utilizing plants from 100 native and 165 non-native populations of *Erigeron canadensis*. These plants were grown under varied conditions, including adequate water and drought, to assess their performance when growing alone, alongside individuals of their own species, and in competition with other plant species. The paper suggests that this competitive advantage evolved independently in different geographical regions.

Genetic analyses identified four distinct clusters of the plant, with increased competitive ability evident in two of these. This finding indicates that similar evolutionary changes can emerge independently, rather than being solely attributable to the spread of a single, already competitive lineage. A crucial discovery was that the competitive advantage was primarily linked to interactions with other species, rather than competition among individuals of the same species. Specifically, non-native plants demonstrated 28.4% greater competitive tolerance and 38% greater competitive suppression.

What to watch: Further research on evolutionary changes in invasive species.

Editor's note: The draft effectively summarizes the scientific findings, methodology, and evolutionary implications of the experiment described in the source.