The taxonomy and distribution of the species of Gambusia (Pisces: Poeciliidae) in Belize, Central America

" Four species of Gambusia are recorded from Belize: G. sexradiata, G. luma, G. nicaraguensis and the G. puncticulata yucatana complex; a key for their identification is presented. G. nicaraguensis is restricted in Belize to either offshore localities in full-strength sea water or river mouths in water of high salinity, and does not occur in fresh water as it does farther south where it is the only species of Gambusia present. G. luma exhibits geographic variation in Belize, the populations in the far southern portion of the country having fewer pectoral-fin rays. Northern and southern Belize populations of G. sexradiata differ in modal number of dorsal-fin rays, depth of the caudal peduncle, and coloration. These differences are discussed in relation to the past geological history of Belize. The G. p. yucatana complex is represented by marine populations at offshore localities and by two forms of G. p. yucatana (slender- and deep-bodied) on the mainland. The taxonomic status of G. p. yucatana is discussed, and information is presented supporting the hypothesis that the differences between these forms have a genetic basis and are not the result of environmental factors "