ISSN 1022-7954, Russian Journal of Genetics, 2007, Vol. 43, No. 12, pp. 1350–1356. © Pleiades Publishing, Inc., 2007.
Original Russian Text © K.A. Truveller, K.I.Chernyshov, 2007, published in Genetika, 2007, Vol. 43, No. 12, pp. 1611–1618.
The taxonomic signiﬁcance of electrophoretic pat-
terns of allozymes used as gene markers has long been
reduced to calculating the genetic distances between
populations of various taxa; such distances are believed
to be proportional to the time elapsed since the diver-
gence of their gene pools . The difference in alloz-
yme patterns of population gene pools is determined by
mutations affecting the corresponding structural genes
and resulting in amino acid substitutions; the gene fre-
quencies are then affected by selection, drift, and isola-
tion. However, the divergence of taxa is accompanied
not only by changes in the frequencies and allele com-
position of loci, but also by their ampliﬁcation and a
regulatory redistribution of their expression, as usually
observed during tissue differentiation in ontogeny .
The relative contributions of these processes to the dif-
ferentiation of animal taxa varying in rank have not
been estimated so far. For such estimation, it is neces-
sary to classify the genetic events underlying the differ-
entiation at various taxonomic ranks and to develop
approaches to the estimation of the contribution for
each particular class.
First, changes in the allele frequencies of a locus are
the most primitive and, probably, most common mech-
anism generating differences without qualitatively
changing the allele composition. This mechanism has
been most extensively studied at the intraspeciﬁc level.
The process is rather stochastic and depends on the
gene drift, founder effects, and selection; the allele
composition remains the same.
Second, the allele composition of a locus is qualita-
tively changed when new alleles arise as a result of
mutations or some existing alleles are lost as a result of
selection and/or gene drift. The allele sets of a locus can
partly overlap or completely differ between different
populations as well as different species. From general
considerations, the difference in allele composition
increases with the increasing rank of the taxa.
Third, a locus can be ampliﬁed with subsequent
functional divergence of the corresponding proteins,
which is then reﬂected in tissue-speciﬁc expression of
the loci during ontogeny. It is possible that duplicated
loci lack structural mutations and remain identical in
allele composition to the original locus; however, the
most common situation is where the loci completely
differ in allele composition. Studies of the tissue speci-
ﬁcity of protein-coding loci in various taxa can help to
understand the signiﬁcance of regulatory changes in the
expressed part of the genome and their role in evolu-
tionary divergence [3, 4]. Repression or derepression of
loci is more rare and, probably, is characteristic of spe-
cies and higher taxa.
Other possible sources of differences in allozyme
sets—translocations, other chromosome rearrange-
ments, horizontal transfer, posttranslational modiﬁca-
tion, etc.—are omitted here.
The above three components contributing to the dif-
ference between taxa are well known and have been
studied to some extent. However, their relative contri-
butions to the evolutionary divergence have not been
estimated as of yet. To obtain such estimates for animal
taxa at the intraspeciﬁc, speciﬁc, and supraspeciﬁc lev-
Contributions of Expression Redistribution
and Allele Substitutions to the Genetic Differentiation
of Animal Taxa of Different Ranks
K. A. Truveller and K. I. Chernyshov
Department of Invertebrate Zoology, Biological Faculty, Moscow State University, Moscow, 119899 Russia;
fax: +7(495) 939-43-09; e-mail: firstname.lastname@example.org
Received September 25, 2006
—The contributions to the genetic differences between animal taxa of various ranks were estimated
for four groups of loci: loci with identical (i), similar (s), or completely different (d) allele compositions, and
(o) loci displaying a change in expression. The main contribution is made by i- and s-loci at the intraspeciﬁc
level. Another pattern is observed at the speciﬁc level: d-loci become dominant and o-loci appear, suggesting
fundamental changes in the genomes upon speciation. The relationships between the contributions of the four
groups of loci are relatively stable within a class and differ among classes. Interestingly, the extent of genetic
differentiation (as estimated from the proportions of the above four components) observed at the speciﬁc level
in amphibians is achieved only at the level of families in birds. The approach is especially efﬁcient for identi-
fying hybrid populations and individuals.