The Evolutionary Theory of
Sex:
Sexual Dimorphism Within One Generation in Stable Environment
Let’s assume that the initial
distribution of genotypes in the population is equal for
male and female zygotes, thus the sexual dimorphism is
absent.
In stable environment different
reaction norm of male and female sex transforms
their similar genotypes into different phenotypes, maximally
adjusted to the environment (Figure
1f). The
phenotypical distribution of the male sex before selection
approximately follows initial genotypic one (Figure
1g), because of a
narrow reaction norm. Distribution of female sex's
phenotypes is more adaptive to the environmental pressure
and can have higher deviation from genotypic one. In stable
environment this narrows phenotypical distribution of the
female sex. High ontogenetic plasticity allows female sex to
leave selection zones, move to a comfort zone and more fully
preserve past genotype spectra. Males stay in dangerous
areas and undergo selection. The influence of the
environment is either in the elimination and discrimination
from reproduction, or in modification but with participation
in reproduction. Due to the different reaction norm, the
elimination and discrimination mainly involve male sex and
modification—female one.
In stable environment ( S )
all transformations of the genetic information involve
variation of the sexes, but did not change the modal values
of traits (Figure
1). Therefore the sexual dimorphism is absent. Only
difference in variation is created, which disappears in the
next generation.
Figure 1
Transformation of genetic information in one generation (n)
in stable (S) environment.
X—genotypes or phenotypes, p—their frequencies in
population. Dashed lines—male sex, reaction norm—β;
dotted lines—female sex, reaction norm—γ.
█—eliminated by natural selection (mainly male sex).
░—rejected
by sexual selection (male sex only). Distributions:
g—genotypes received from generation n-1 (zygotes);
f—phenotypes, realized from g (before and after selection);
q—genotypes transmitted to generation n+1;
v—genotypes received from generation n (zygotes).
Continue to :
Sexual Dimorphism Within One Generation in Changing Environment
Dimorphism and Dichronism in Phylogeny
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