Amphi-panamic geminates of snook (Percoidei : Centropomidae) provide a calibration of the divergence rate in the mitochondrial DNA central region of fishes

The mitochondrial DNA control region is one of the most frequently utilized sequences for both intra- and interspecific genetic studies of fishes, yet a tenable divergence rate specifically for fish control regions has not be en established. We attempted to establish a rate through a comparative stud y of control region sequences and those of a protein-coding mitochondrial g ene region from geminate species of snook (Centropomus) assumed to have bee n separated by the emergence of the Isthmus of Panama 3.5 million years ago . The divergence rate suggested from the control region alignments between the geminates was markedly higher than rates currently applied in many stud ies, as was the rate suggested from the ND 5/6 protein coding region alignm ents. However, the suggested ND 5/6 rate when applied to alignments with th e outgroup species was not concordant with the scant centropomid fossil rec ord and therefore the assumed separation time of 3.5 million years seemed i mplausible. An average control region divergence rate was then estimated ba sed on separation times of snook species derived assuming a divergence rate of 1% per million years for transversion substitutions at third codon posi tions in the ND 5/6 region. Using these separation times, a tenable average divergence rate for fish control regions of approximately 3.6% per million years +/- 0.46% SE was calculated. (C) 1999 Academic Press.