Invaders get better at competition in introduced ranges: Study

Are invasive plants better at competing with species in places they invade than species in their native range? A paper investigated this using Erigeron canadensis, commonly known as Canadian horseweed, to find that plants from non-native populations had 19.2% higher competitive ability than those from native populations. In the study, that advantage was evident across two watering conditions — watered and drought. Although drought reduced competitive ability overall by 12.9%, the difference between native and non-native populations was not significant. Canadian horseweed is native to North and Central America that has spread widely across Europe, Asia and other regions. In some introduced areas, it can suppress other plant species and reduce local plant diversity. The researchers conducted a large glasshouse experiment involving plants from 100 native and 165 non-native populations of Erigeron canadensis. They grew the plants under different conditions, including adequate water and drought, and tested how they performed when growing alone, alongside individuals of their own species, and alongside other plant species. The paper suggests that the competitive advantage evolved independently in different regions. Genetic analyses identified four clusters, but increased competitive ability was evident in two. The result suggests that similar evolutionary changes can emerge independently rather than being explained solely by the spread of one already competitive lineage. One of the crucial findings was that the advantage was associated with interactions with other species, rather than competition between individuals of the same species. Non-native plants showed 28.4% greater competitive tolerance and 38% greater competitive suppression under…This article was originally published on Mongabay