------------------------------------------------------------ Pushpakumata, G., Thattil, R., Marambe, B., Silva, P., Athauda, S. and Weerakoon, D. (2010): A conceptual framework for quantitative assessment of the invasiveness of alien species in Sri Lanka. In: Invasive Alien Species in Sri Lanka – Strengthening Capacity to Control Their Introduction and Spread (Eds: Marambe, B., Silva, P., Wijesundara, S. and Atapattu, N.), pp 87-94. Biodiversity Secretariat of the Ministry of Environment, Sri Lanka. Review paper A Conceptual Framework for Quantitative Assessment of the Invasiveness of Alien Species in Sri Lanka Gamini Pushpakumara¹, Raphel Thattil¹, Buddhi Marambe¹, Pradeepa Silva¹, Saman Athauda¹ and Devaka Weerakoon² ¹Faculty of Agriculture, University of Peradeniya, Sri Lanka ²Faculty of Science, University of Colombo, Sri Lanka Introduction Plant and animal invasions are considered as a serious threat to biodiversity, and are second only to man-made habitat loss and fragmentation. Invasive alien species (IAS) are known to cause significant reductions in native species populations, severe alterations of native plant and animal communities, or make significant changes to ecosystem processes and parameters (Bratton, 1982; Gordon, 1998; Hobbs and Mooney, 1998; Vitousek, 1986; Wilcove et al., 2000). Identification of invasiveness prior to their introduction (i.e. risk assessments), and ranking or grouping of already established invasive species using predictive tools will be a crucial step in the decision making process for managing invasive species (see Chapter 3 for details). Some countries have already used qualitative criteria to develop a numerical index, which allows grouping IAS based on selected criteria to facilitate the decision-making process in their management and prioritization of species for necessary action. However, in Sri Lanka, scientifically valid qualitative or quantitative assessments of invasiveness or risk assessment of plant or animal species have not taken place formally, yet. Protocols developed by Hafiz et al. (2006) for plants and Weerakoon (2007) are not widely available or have limited applications. Although there are different lists of IAS reported for Sri Lanka (Bambaradeniya, 2000, 2002; Marambe et al., 2001, 2003; Wijesekera and Bambaradeniya, 2007), information on qualitative or quantitative aspects of invasiveness have not been used in preparing these lists of species. Chapter 8