Colonization occurs when a species enters and spreads into a new geographic area or habitat. This process involves both the initial entry, or invasion, into the new area by the species and its successful establishment there, which includes finding adequate resources for growth and reproduction. Less commonly, the term may be used when a parasite enters into and spreads inside a host or when a gene enters into and spreads within a new population.

The process of colonization is intensively studied along with theories of island biogeography because islands are discrete, measurable areas where colonization occurs. Island biogeography is the study of the dynamics that effect populations of isolated areas, and that encompasses the entire process of colonization. Island biogeography theories can be divided into three types. The first relates to habitat diversity and focuses on the suitability of the new habitat for the invading species. The second...