title: Phylogenetic utility of the tyrosine kinase gene X-src for assessing relationships among representative cichlid fishes.
abstract: The nuclear gene X-src is a member of the tyrosine-kinase class of proto-oncogenes whose normal product is localized within the cytoplasm of the cell. The X-src gene has been used in only a few phylogenetic studies, each focusing on systematics of killifishes (Cyprinodontiformes). The present study is an attempt to examine the phylogenetic utility of X-src for uncovering relationships of representative cichlid fishes, especially the cichlids of Middle America. The family Cichlidae is a species-rich group of tropical freshwater fish made up of more than 1000 species which show a Gondwanan pattern of distribution. Cichlid fish have been the focus of numerous studies ranging from behavioral to biogeographical to systematic in nature. Particular emphasis has focused on the cichlids of the African Great Lakes and the explosive adaptive radiation of this group. However, Neotropical cichlids have received considerably less attention than their African counterparts. Our findings regarding the utility of X-src concur with those of previous phylogenetic analyses showing the exons of X-src to be highly conserved and useful mostly for revealing deep relationships among taxa. Like previous X-src studies, we also found the intron sequences of the gene to be variable in length and difficult to align across distantly related taxa but they provided useful information for resolving relationships among more closely related taxa. The X-src phylogeny supports the monophyly of Neotropical cichlids and cichlasomines groups A (=heroines) + B (=cichlasomines). A highly resolved tree is obtained within the heroines but little support is evident for most nodes based on the low number of unambiguous substitutions. The X-src gene is likely to be quite useful for resolving deep phylogenetic relationships such as those among major groups of actinopterygian fishes.
authors.affiliation: Department of Biological Sciences, Biodiversity and Systematics, Tuscaloosa, Alabama 35487, USA.
authors.forename: J
authors.initials: J
authors.lastname: Sides
authors.forename: C
authors.initials: C
authors.lastname: Lydeard
mesh_terms: D000818:Animals; D001483:Base Sequence; D003062:Codon; D017124:Conserved Sequence; D005091:Exons; D016391:Genes, src / Q000235:genetics*; D007438:Introns; D008969:Molecular Sequence Data; D010471:Perches / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
chemical_list: D003062:Codon; D011505:Protein-Tyrosine Kinases