Address on “Why plant species become invasive? – Characters related to successful biological invasion”

Abstract

The impact of Invasive Plant Species (IPS) on biodiversity is irreversible and enormous because plant invasions can alter the functioning of an ecosystem dramatically. They also have a negative impact on environmental, economic and public wellbeing. Invasiveness of a species is dependent on any of five key factors: regional climate, microclimate, the site, past disturbance patterns, and individual species characteristics. The main focus of this paper is on species characteristics. Invasive species show high reproductive fecundity and great capability of spreading throughout their new location. Invasive species have characteristics that allow them to thrive in the area where they are introduced. However, how the characters of invasive alien species (IAS) determine their invasiveness is one of the key questions in invasion biology and this paper describes key characters of IPS, which are of great significance for their invasiveness. Compared to the native specialists‘ plants, the IPS are generalists, capable of surviving in a wide range of climatic conditions, which produce diverse habitats and soil variations. Therefore, IAS possess a broad habitat compatibility. In their new environment, IPS are not subjected to the damages of natural herbivores and diseases to maintain their maximum population densities, and hence they monopolize habitats. IPS enhances their invasive habit successfully by efficient competition for resource utilization and creating allelopathic effects to native biota. Invasive species also have high rates of growth and reproduction with early maturity. As a result, invasive species flourish in the settled landscapes as they produce many offspring and spread in to new area rapidly (high reproductive fecundity). Phenotypic plasticity and genetic differentiation are the two major strategies of IAS, which facilitate them to adapt to new habitats and environmental heterogeneity. Characteristics that make IPA successful in our environment are discussed with appropriate examples from IPS of Sri Lanka. However, generalizations can be misleading, because studies reveal different responses of native plants to the presence of IPS. Therefore, there is a need to understand general trends and exceptions within a particular habitat.