Morphological Differentiation Between Introduced and Native Populations of Three Species of Cichlid (Perciformes)

Fishes of the family Cichlidae are well known for their capacity to exploit trophic niches in their environments through rapid speciation and morphological diversification, with the best-documented cases of such diversification occurring in the lakes of the African Rift Valley. Numerous species of cichlids are established outside of their native ranges, with reproducing populations of many species occurring in southern Florida (U.S.). The purpose of this study was to examine morphological differences between native and non-native (Floridian) populations of three cichlid species ( Pelmatolapia mariae , Parachromis managuensis , and Mayaheros urophthalmus ) to better understand how these species have managed to invade so successfully. Using linear measurements, we found that all three species have diverged in multiple characteristics: Pe. mariae in head length (HL), snout length (NL), and interorbital width (IO), Pa. managuensis in maximum body depth (MD), NL, and IO, and M. urophthalmus in MD and IO. Analyses of 2D-landmark data also revealed that Pe. mariae and Pa. managuensis collected from non-native populations display morphological variation beyond the ranges of variation exhibited by specimens from native populations. The observed morphological differences may be the result of natural selection, morphological plasticity, or some combination of the two; further work is needed to test these hypotheses. This study suggests that the conditions exist to promote rapid morphological change in introduced populations of cichlids in Florida.