From Phytochemistry to Invasion: A Critical Review of Allelopathic Mechanisms and Ecological Impacts of Three Invasive Asteraceae Species in the Eastern Ghats, India

Invasive alien plants increasingly threaten biodiversity and ecosystem function by altering native plant communities through disproportionate ecological interactions. This review synthesizes and critically evaluates published evidence on the phytosociology, phytochemistry and allelopathic potential of three dominant invasive Asteraceae species, Parthenium hysterophorus L., Chromolaena odorata (L.) R.M. King and H. Rob., and Tridax procumbens L., which contribute to ecological imbalance and reduced native plant regeneration in the Eastern Ghats of peninsular India. Evidence from the Eastern Ghats and comparable tropical landscapes is reviewed to assess the roles of phenolics, alkaloids, terpenoids, flavonoids and sesquiterpene lactones in suppressing native vegetation and modifying soil–plant interactions. The applicability of the novel weapons hypothesis to these co-occurring invaders is also examined. The synthesis highlights relationships between phytochemical diversity and invasion mechanisms and identifies important knowledge gaps concerning species- and site-specific effects. A conceptual and methodological framework integrating field-based phytosociological assessment, phytochemical characterization and controlled allelopathic bioassays is proposed to guide future research on bio-management and ecosystem restoration. Such an integrated approach could support sustainable invasive species control while reducing reliance on broad-spectrum chemical management. The review provides an ecologically informed basis for managing invasive Asteraceae and conserving native vegetation in the Eastern Ghats and other vulnerable tropical ecosystems.