SREL Reprint #1973





Cytochrome b sequence variation and a molecular phylogeny of the live-bearing fish genus Gambusia (Cyprinodontiformes: Poeciiiidae)

Charles Lydeard, Michael C. Wooten, and Axel Meyer

Abstract: Nucleotide sequences for a 402-base segment of the mitochondrial cytochrome b gene were determined from 25 species of live-bearing fishes. A total of 34 sequences representing 24 species of the genus Gambusia and 1 species of Belonesox were generated via the polymerase chain reaction. The levels of overall variation were consistent with those from other genera of fishes. In total, 137 of 402 (34.1 %) nucleotides exhibited variation within or among the species. Observed differences at 24 (17.9 %) of the 134 cytochrome b codons would result in amino acid replacements. Phylogenetic analyses employing various weighting schemes resulted in several clades representing traditionally recognized taxonomic groups. However, precise relationships among species-groups remained uncertain. Randomization tests indicated that these topologies contained significant nonrandom phylogenetic information. As with other fishes, the overall rate of divergence appeared to be slower than that of other vertebrates and the overall replacement/substitution pattern was suggestive of nonrandom evolutionary input.


SREL Reprint #1973

Lydeard, C., M.C. Wooten, and A. Meyer. 1995. Cytochrome b sequence variation and a molecular phylogeny of the live bearing fish genus Gambusia (Cyprinodontiformes: Poeciliidae). Canadian Journal of Zoology 73:213-227.

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