Of the forty-four species in genus Gambusia, nine are Vulnerable; one, G. eurystoma, is Critically Endangered; and two, the amistad gambusia (G. amistadensis) and the San Marcos gambusia (G. georgei), are already extinct.
"Gambusia" (http://www.fishbase.org/Eschmeyer/GeneraSummary.cfm?ID=Gambusia). FishBase. Ed. Ranier Froese and Daniel Pauly. October 2004 version. N.p.: FishBase, 2004.
"Gambusia" (TSN 165877) (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=165877). Integrated Taxonomic Information System. N.p.: Integrated Taxonomic Information System, 2004. Accessed on 12 December2004.