Evolutionary Explanation for Invasive Abilities of Centaurea stoebe (spotted knapweed) in Introduced Areas Invasion and its effects on biodiversity in native areas

Exotic species are those which have been dispersed, either by chance or human action, to an environment outside of their native range. Only a small portion of these exotics are able to become well established in the invaded population and even expand beyond it. The ones that can are termed invasive species (Muller-Scharer, Schaffner & Steinger, 2004; Bais et al., 2003). Broz et al. (2007) estimates that 25,000 species of invasive plants are in the U.S. invading 700,000 hectares of United States wildlife habitat per year and tallies the economic burden of invasive plant species to be around $35 billion dollars annually. Most pressingly, invasive species pose a significant threat to biodiversity. They threaten biodiversity by outcompeting native plants and becoming dense in the populations they invade. This presents a real threat to the economy and environment (Prentis et al., 2008). In fact, biological invasions are thought to be the second leading cause of biodiversity loss in today’s world, after habitat fragmentation (Keane & Crawley, 2002). For example, 50% of Hawaii’s native plant species are endangered and 200 have already gone extinct, largely driven out by introduced invasive species (Broz & Vivanco, 2009). There is even some concern in the scientific community that invasive species may have the potential to instigate evolutionary changes in native species (Lee, 2002)