Theory of Asynchronous Evolution


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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—
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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