Biological invasions across multiple continents are akin to large-scale transplant experiments and can provide a chance opportunity to study eco-evolutionary phenomenons. The spread of the Asteraceae Ageratina adenophora is of global concern, as it has been recognized as a noxious invasive plant species in numerous countries. Native to Mexico, this apomictic, triploid plant is highly invasive in moist subtropical and sub-temperate montane regions. Using Ageratina adenophora as a model species and employing a suite of experimental and macroecological methods at different spatial scales, I have attempted to answer several questions of evolutionary and ecological significance in this thesis. I found that 1) Ageratina adenophora has a unimodal pattern of distribution along elevational gradient in western Himalaya. 2) Ageratina adenophora has not undergone any rapid evolutionary changes along an elevational gradient in western Himalaya 3) The niche of Ageratina adenophora has expanded considerably in Asia and Australia. The thesis highlights the risk of invasion despite absence of evolutionary changes.