ISSN 1062-3604, Russian Journal of Developmental Biology, 2009, Vol. 39, No. 3, pp. 145–149. © Pleiades Publishing, Inc., 2009.
Original Russian Text © S.D. Grebelnyi, 2009, published in Ontogenez, 2009, Vol. 39, No. 3, pp. 185–190.
Unisexual reproduction occurs in quite different
animalian groups. The absence of the second progeni-
tor inevitably results in more or less steady cloning—
more or less strict repetition of individual genotype in
many generations. Since males are not able to breed
without females, cloning brings about to the appear-
ance of all-female races or species in most cases, which
are not numerous in nearly all taxa. The majority of uni-
sexual species known to date are supposed to be (and
likely are) parthenogenetic. However, some other kinds
of reproduction and unisexual inheritance have been
recorded in a few species.
Avoidance of the normal sexual reproduction can
produce the genetic effect of different sorts. Being
dependent on particular mechanisms of preservation of
the parental somatic chromosomal number in offspring,
it can vary from inheritance of only maternal features to
complete substitution of maternal for paternal ones.
Anyway, it seems obvious that any unusual rearrange-
ment of the genetic material, while reproducing,
abruptly changes the characteristic features of the
“Mendelian population,” which are considered to be the
base of the commonly accepted concept of speciation
(Dobzhansky, 1937; Timoféeff-Ressovsky, 1939; Mayr,
1942, 1963; Simpson, 1944; Timoféeff-Ressovsky et al.,
1969, 1973; Vorontsov, 1980, 2004).
During parthenogenesis, the juvenile originates
from an egg without any participation of spermatozoa.
Fertilization does not occur, that is why in such a case
the complete (non reductional) diploid or polyploid
chromosome set of somatic cells is to be preserved in
the egg. In natural populations, parthenogenesis is
always connected to deep disintegration of meiosis that
leads to a complete stoppage of genetic recombination,
so that the maternal characters are inherited by the off-
spring without any changes.
When discussing the origination of parthenogenetic
forms and inevitable competitive interactions of them
with their closest bisexual relatives, one quite often
considers the “double advantage” of parthenogenesis
(Maynard Smith, 1978) that gives the population an
opportunity not to spend 50% of environmental
resources on males. According to another, maybe more
reasoned point of view, the advantages of parthenoge-
netic populations could be caused by their higher het-
erozygosity and genotypic uniformity of individuals
rather than by higher rate of breeding without males
(Suomalainen, 1969; Suomalainen and Saura, 1973,
Suomalainen et al., 1976; Grant, 1977; Grebelnyi,
The parthenogenetic-like effect is also produced by
some other secondary modiﬁcations of sexual repro-
duction, which include
. Gynogenetic and hybridogenetic
forms also generate mainly all-female populations, but
their reproduction requires the participation of males of
closely related bisexual species. Unlike them, androge-
netic populations could be found only among hermaph-
Unisexual Reproduction: Either Maternal
or Paternal Inheritance
S. D. Grebelnyi
Zoological Institute, Russian Academy of Sciences, Universitetskaja nab. 1, St-Petersburg, 199034 Russia
Received November 3, 2008; in ﬁnal form, December 8, 2008.
is usually recognized as the most accepted mechanism of cloning, i.e., reproduc-
tion without genetic recombination. Transfer from bisexual to parthenogenetic propagation causes the appear-
ance of all-female populations, races, and species. It was ascertained in natural populations of numerous of rep-
tile and insect species. Clonal and hemiclonal species of ﬁshes and amphibians propagate by means of
. Less known are instances of
found in some insects and mollusks. In
this case offspring develops only under control of male genes supplied by spermatozoa. Mother’s genes
included into the egg nucleus have to be entirely lost. Androgenesis may be called mirroring of parthenogenesis.
: unisexual species, cloning, parthenogenesis, gynogenesis, androgenesis, hybridogenetic com-
Bacillus, Corbicula, Rana, Poecilia, Poeciliopsis, Menidia, Cobitis, Bombyx.