Jung-Ti Chang

Publication Date


Document Type


First Advisor

Greenfield, David W.||Wildrick, David M.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences


Gambusia; Poeciliidae; Electrophoresis; Fishes--Classification


A cladistic approach was used to assess relationships among eleven poeciliid fishes of the genus Gambusia. A cladogram was constructed utilizing data from the analysis of a total of 86 variable enzyme products (electromorphs) of 26 gene loci. A Wagner tree was constructed using Rogers’ genetic distance matrix, using Brachyrhaphis terrabensis as the outgroup taxon. Based on the Gambusia hypothetical phylogenetic tree derived from biochemical data, G. vittata is not the sister group of all the other Gambusia species as previously proposed by Donn E. Rosen. Rather, G. luma is the sister group of the other Gambusia species, thus putting luma in a separate species group. G. sexradiata is distinct from G. luma, suggesting that neither luma nor sexradiata belong to the punctata species group as proposed by D. E. Rosen and Reeve H. Bailey nor do they belong to the nobilis species group of Luis R. Rivas. There is a close relationship between rhizophorae and xanthosoma from both phenetic (Nei D = 0.112) and cladistic (synapomorphic allele 6-PGD^(a)) viewpoints, suggesting that they do belong in the punctata species group. Based on the available biochemical data, G. nicaraguensis is the sister group of rhizophorae and xanthosoma, and G. affinis is the sister group of G. vittata, G. regani and G. panuco. These sister group relationships based on the biochemical data are questionable because of the lack of representation of many Gambusia species and the fact that the computer program clustered those representatives that were present. The lack of clustering, however, does have taxonomic significance. A biochemical key to the Gambusia species studied is provided along with a listing of their plesiomorphic, synapomorphic and autapomorphic alleles.


Bibliography: pages 90-94.


vii, 94 pages




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