Salmonid opsin sequences undergo positive selection and indicate an alternate evolutionary relationship in oncorhynchus.
Positive selection can be demonstrated by statistical analysis when non-synonymous nucleotide substitutions occur more frequently than synonymous substitutions (dN>dS). This pattern of sequence evolution has been observed in the rhodopsin gene of cichlids. Mutations in opsin genes resulting in amino acid (AA) replacement appear to be associated with the evolution of specific color patterns and the evolution of courtship behaviors. Within fish, AA replacements in opsin proteins have improved vision at great depths and have occurred in deep-sea species. Salmonids experience diverse photic environments during their life history. Furthermore, sexual selection has resulted in species-specific male and female coloration during spawning. To look for evidence of positive selection in salmonid opsins, we sequenced the RH1, RH2, LWS, SWS1, and SWS2 genes from six Pacific salmon species as well as the Atlantic salmon. These salmonids include landlocked and migratory species and species that vary in their coloration during spawning. In each opsin gene comparison from all species sampled, traditional dN:dS analysis did not indicate positive selection. However, the more sensitive Creevey-McInerney statistical analysis indicates that RH1 and RH2 experienced positive selection early in the evolution and speciation of salmonids.
Dann
Stephen G
SG
Department of Biology, University of Victoria, P.O. Box 3020 STN CSC, Victoria, British Columbia, Canada V8W 3N5.
Allison
W Ted
WT
Levin
David B
DB
Taylor
John S
JS
Hawryshyn
Craig W
CW
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D019143:Evolution, Molecular; D017686:Oncorhynchus mykiss / Q000235:genetics*; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017299:Rod Opsins / Q000235:genetics*; D012641:Selection, Genetic
D017931:DNA Primers; D018076:DNA, Complementary; D017299:Rod Opsins