The article reviews the evidence for phenotypic and genetic differentiation between native and introduced plant populations, focusing on the Evolution of Increased Competitive Ability (EICA) hypothesis. Field studies suggest that introduced plant populations often exhibit increased growth and reduced herbivore damage, indicating enemy release. Molecular studies show that genetic diversity in introduced populations is not consistently different from native populations, and multiple introductions are common. Common garden experiments and phenotypic plasticity studies further support the EICA hypothesis, with introduced populations showing increased growth and decreased resistance. However, few studies fully test both growth and defense in the same species. The review discusses methodological issues in cross-continental comparisons and suggests future research directions, emphasizing the need to address evolutionary changes in traits beyond defense and growth.The article reviews the evidence for phenotypic and genetic differentiation between native and introduced plant populations, focusing on the Evolution of Increased Competitive Ability (EICA) hypothesis. Field studies suggest that introduced plant populations often exhibit increased growth and reduced herbivore damage, indicating enemy release. Molecular studies show that genetic diversity in introduced populations is not consistently different from native populations, and multiple introductions are common. Common garden experiments and phenotypic plasticity studies further support the EICA hypothesis, with introduced populations showing increased growth and decreased resistance. However, few studies fully test both growth and defense in the same species. The review discusses methodological issues in cross-continental comparisons and suggests future research directions, emphasizing the need to address evolutionary changes in traits beyond defense and growth.