They also carry with them the threat of new diseases that can destroy vulnerable native inhabitants. In some areas, native species are on the brink of extinction due to the introduction of an exotic species. Occasionally, exotic species reproduce with natives and produce hybrids. Hybrids not only change the gene pool of an area, they also simplify an ecosystem. By simplifying an ecosystem, as well as causing population declines and species extinctions, exotic species can reduce biodiversity.
Biodiversity is the variation and variety of genes, organisms and species found in an ecosystem.
As biodiversity decreases, the vulnerability of an ecosystem to pests and diseases increases. Because the makeup of communities is not always studied, when biodiversity decreases, it is not noticed. It is important to have naturalist biologists who can identify which species are indigenous and which are not, as well as which have disappeared. Introductions do not always have a negative impact. Exotic species can help an ecosystem by providing a missing link in a failing food chain.