Adaptations of phytophagous insects on invasive host plant species

Since humans have started travelling and colonizing new areas they have brought animals and plants along with them, introducing them into new environments. Sometimes these introductions happened intentional; livestock, garden plants and crops for example, but sometimes they happened unintentional for example, rats and plant seeds. This human-influenced geographic shuffling of organisms is probably the most biologically dynamic of anthropogenic ‘global change’ phenomena (Carroll, 2007b). A lot of these introduced species do not survive or reproduce in their new habitats due to unsuitable conditions, or are outcompeted by native species and do not become established. Some species however, have managed to become established. This is especially the case in disturbed habitats (Davis et al., 2000; Rejmanek et al., 2004). Disturbed habitats lose constituent species and nonnative species can become established by accessing the resources left unused by these constituent species (Fargione & Tilman, 2005; Levine et al., 2004), or because the nonnative species are better adapted to disturbed habitats than the native species (Burke & Grime, 1996; Strauss et al., 2006b). Another factor determining whether a nonnative species becomes established is whether they can escape natural enemies in ways that give them a competitive advantage over native species (Colautti et al., 2004; Joshi & Vrieling, 2005; Stastny et al., 2005). Therefore whether a nonnative species becomes established depends on both the ecological circumstances of the habitat and the genetic variability of the introduced species (Carroll, 2007b). If established populations of a nonnative species grow and spread due to successful reproduction and recruitment of subsequent generations into the breeding population, that species may become prominent in the native biota or ‘invasive’ (Parker et al., 1999; Richardson et al., 2000). Invasive species may even become dominant to native populations (Crooks, 2002; Davis & Thompson, 2000).