One of the largest threats that can result in the failure of an introduced population is the genetic bottleneck and subsequent inbreeding depression that can result from such a small population size. There are a numerous methods through which an invading population can overcome the deficit to fitness brought on by a lack of genetic diversity that reduces species fitness. As time advances with an invasion it is possible for an invasive population to have a higher genetic diversity then in it native population. One reason for this is hybridization, which doesn’t always occur between two separate species. In many cases the hybridization is interspecific, which is known as admixture.
Genetic Admixture occurs when populations of the same species that were geographically separate in the there native habit breed in a novel habitat that is new to both populations. Naturally it can occur as the result of the creation of an isthmus or another event that connects two previously isolated populations but most of the cases of modern admixture are human mediated. This mixing of populations can work in the benefit of the novel population for many reasons because it provides an influx of genetic variation to overcome the bottleneck and mask deleterious alleles. This genetic influx allows a recombination of alleles to create genes not seen in the native habit, which can increase fitness in a new environment.One of the chief costs associated with admixture is that the new populations can re-introduce negative alleles into a population that natural selection has weeded out.
1. Verhoeven, K. J. F., M. Macel, L. M. Wolfe, and A. Biere. "Population Admixture, Biological Invasions and the Balance between Local Adaptation and Inbreeding Depression." Proceedings of the Royal Society B: Biological Sciences 278.1702 (2010): 2-8. Web. 12 Apr. 2015.
2. Roman, J., and J. Darling. "Paradox Lost: Genetic Diversity and the Success of Aquatic Invasions." Trends in Ecology & Evolution 22.9 (2007): 454-64. Web. 12 Apr. 2015.