Invasion of Plant Communities

Due to numerous human activities, organisms have been transported and either accidentally or deliberately introduced all around the globe. Biological invasions are now considered to be one of the main drivers of global change because many invasive plants have severe ecological, economic, and health consequences. Thus, there is an ever-growing need to better understand invasions to determine how specific plant species are able to establish in communities and, in many cases, expand their range. Here, we describe the invasion process and how it contributes to the invasion of plant communities. We present an invasion-factor framework (IFF) model that uses three factors (climate dynamics, ecosystem resistance, and invader fitness) to explain how each plays a role in the introduction of plants and their ultimate failure or success (i.e., becoming invasive). The invasion of plant communities starts with the uptake of propagules from the native range, followed by their transport to and release into a new territory, where they become established and can spread or expand. Propagule pressure, prior adaptation, anthropogenically induced adaptation to invade, and post-introduction evolution are several theories that have been posed to explain the establishment of invasive plants. Further, traits of invasive plants, either before (existing) or after (developed) introduction, provide a mechanistic understanding with direct ties to the three factors of the IFF. The IFF is a general guide with which to study the invasion process based on specific factors for individual invaders and their target communities. The IFF combines (a) climatic dynamics, analogous to environmental filters; (b) ecosystem resistance, which prevents invasive plants from becoming established even if they are able to overcome the climate factor; and (c) invader fitness, relating to the genetic diversity of invasive plants, which allows them to become established after overcoming climate and ecosystem resistance