1063-0740/00/2606- $25.00 © 2000
Russian Journal of Marine Biology, Vol. 26, No. 6, 2000, pp. 432–438.
Original Russian Text Copyright © 2000 by Biologiya Morya, Oleinik.
Our previous studies of phylogenetic relationships
in some species of the family Salmonidae have shown
a high degree of correspondence in the dendrograms
constructed for the mitochondrial and nuclear genes [5,
6]. The phenograms differ topologically in the branches
for the Sakhalin huchen
For the huchen, all
points of branching are equally probable, considering
the level of divergence and the limitations of the statis-
tical methods [23, 24]. The similarity of the masu
salmon with the Paciﬁc trout, based on nuclear DNA
(see Fig. 1a), or with the coho and chinook salmon,
based on mtDNA (see Fig. 1b), is determined by the
evolutionary traits of the nuclear and mitochondrial
genomes. The results of previous studies make it possi-
ble not only to suggest a likely sequence of divergence
of the investigated salmonids , but also to compare
the mutation rates of the independently inherited
regions of the genome.
When the divergence time of taxa is assessed using
protein electrophoresis data and mitochondrial DNA
(mtDNA) analysis, the molecular clock is calibrated
from a particular event, the actual geological time of
which is known . Obviously, the best independent
markers of such events are provided by paleontological
records. Unfortunately, the paleontological material on
salmonid ﬁshes is very scanty [9, 14–16, 28, 29, 33, 35,
37]. Because of poor preservation, the identity of fossil
ﬁsh remains is often dubious, and it is impossible to use
them to calibrate a molecular clock. In this situation,
the prognostic value of a proposed hypothesis may be
judged from the correlation between molecular–biolog-
ical and geological estimates of divergence time.
Therefore, when estimating the rates of molecular
mutation, we have made an attempt to use paleontolog-
ical and geological data to substantiate conclusions.
MATERIALS AND METHODS
The study was performed on 12 species of salmo-
nids from rivers of the Russian Far East: the chum
(Walb.), and chinook
(Walb.), the rainbow trout
, the Dolly
(Walb.), the char
(Glubokovsky), the white-spotted char
(Pallas), and the huchen
Alleles and mtDNA fragments were the examined char-
acters of nuclear and mitochondrial genomes, respec-
tively. Details of methodical approaches, estimated
genetic distances, and schemes of divergence of mito-
chondrial and nuclear genomes are given in previous
papers [3, 5, 6].
An electrophoretic molecular clock can be theoreti-
cally calibrated on the basis of the equation for estimat-
ing genetic distance . At present, the selection of
particular calibration values is quite arbitrary. Never-
theless, along with Nei’s theoretical coefﬁcient of 5
, the calibration scale most frequently used in
ﬁsh studies is that in which there are 19 million years
for a unit of genetic distance .
The divergence time of salmonids was estimated
using two theoretical coefﬁcients of proportionality.
On the Mutation Rates of the Mitochondrial
and Nuclear Genomes of Salmonid Fishes
A. G. Oleinik
Institute of Marine Biology, Far East Division, Russian Academy of Sciences, ul. Pal’chevskogo 17, Vladivostok, 690041 Russia
Received January 31, 2000
—Mutation rates of the mitochondrial and nuclear genomes of salmonid ﬁshes were assessed on the
basis of a phylogenetic study of 12 species representing four genera of the family Salmonidae. Analysis of the
extent of divergence of the masu salmon
and the Paciﬁc trout
suggests a high
rate of mtDNA mutation in the masu salmon. However, the nuclear genome in this species has mutated rela-
tively slowly. For the other 5 species of Paciﬁc salmon, no discrepancy was found in the mutation rates of mito-
chondrial and nuclear DNA. Values of the absolute time of divergence of taxa, calculated for the two indepen-
dently inherited parts of the salmonid genome, were approximately within the same range and coincided with
those based on evolutionary hypotheses [1, 21].
Mutation, phylogeny, nuclear DNA, mitochondrial DNA, salmonid ﬁshes, divergence time.