The Gulf Killifish live in the Houston Ship Channel, which is in close proximity to the northwest coast of the Gulf of Mexico. The Atlantic Killifishes (sometimes called 'mummichogs') are also known for their ability to tolerate heavily polluted east coast rivers. The Atlantic Killifish, whose home range is nearly 1,500 miles away from the Houston Ship Channel, were likely brought there by shipping activities. Specifically, it seems that the Atlantic Killifishes' genes entered the Gulf Killifishes' after hybrids of the two species continued to reproduce with non-hybridized members of the Atlantic and Gulf Killifishes' populations over the course of multiple generations. This process, known as adaptive introgression, is what has allowed the Gulf Killifish to survive in these highly polluted environments.

Source: Forbes May 04, 2019 18:00 UTC