This document outlines a population genetic model that shows how sex-specific maternal effects can drive the evolution of sexual conflict. The model examines scenarios where maternal allocation favors one sex over the other, even if only slightly. It finds that under these conditions, maternal effects can cause the population equilibrium to become sub-optimal for both sexes, driving the evolution of sexual conflict without requiring genetic linkage between the sexes. The key implication is that sexual conflict may readily evolve whenever maternal effects create even small imbalances in allocation between male and female offspring.
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Another title for Psionic Comics, The Guardian Seed #1 is a space adventure of an alien from a dying planet, destined to find a way to help his world live on. Included in this issue is the short story Strange Domain, which is part of another series of shorts, plus a presents title. Strange Domain #1 follows the tale of lizard-mouse, as the god of Strange Domain narrates the premise of what will the future of those strange tales.
6. Maternal Generation Offspring Generation
Maternal effects
Phenotype,
ZO
Genetic
Component, GO
Environmental
Component, EO
Phenotype,
ZM
Genetic
Component, GM
Environmental
Component, EM
Cross-Generational Effects on Inheritance
7. Maternal Generation Offspring Generation
Maternal effects
Phenotype,
ZO
Genetic
Component, GO
Environmental
Component, EO
Phenotype,
ZM
Genetic
Component, GM
Environmental
Component, EM
Cross-Generational Effects on Inheritance
Sexual conflict theory needs to consider the role of
maternal effects.
8. Sex-Specific Maternal Effects
• Maternal effects often depend on offspring sex
– Egg-laying order & offspring growth in birds (Badyaev
2006)
– High early fertility of daughters from promiscuous mothers
in Drosophila (Priest et al. 2008)
9. Sex-Specific Maternal Effects
• Maternal effects often depend on offspring sex
– Egg-laying order & offspring growth in birds (Badyaev
2006)
– High early fertility of daughters from promiscuous mothers
in Drosophila (Priest et al. 2008)
• Sex allocation theories predict sex-specific maternal
favouritism (Trivers & Willard 1973; Charnov 1982)
– Sex ratio adjustment
– Offspring quality adjustment
11. Population Genetic Model of Sex Allocation
• Assumptions:
– One locus with 2 alleles: A1 A2, with frequencies of p1 & p2
– Either directly or maternally expressed
– Sex-specific fitness with random mating in infinite
population
19. Population Genetic Model of Sex Allocation
• Fitness
• Evolution
Maternal and direct effects contribute equally to fitness.
But, maternal effects contribute only half as much to evolution.
20. Scenarios of Conflict Evolution
• Assuming conflicting alleles, can sex-specific
maternal effects increase the intensity of sexual
conflict?
1. Additive Genetic Effects
2. Dominance Genetic Effects
• Assuming no allelic conflict, can sex-specific maternal
effects generate sexual conflict?
3. Additive + Dominance Genetic Effects
26. ♀
♂
♂+♀
Additive Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
No net change under
Mendelian inheritance.
No selection for conflict
27. Additive Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
♀
♂ No net change under
Mendelian inheritance.
No selection for conflict
28. Additive Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
♀
♂
♂+♀
No net change under
Mendelian inheritance.
No selection for conflict
But, evolution towards
maximum sexual
conflict with maternal
effects.
34. Dominance Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
♂+♀
♀
♂
No net change under
Mendelian inheritance.
No selection for conflict
35. Dominance Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
♀
♂
No net change under
Mendelian inheritance.
No selection for conflict
36. Dominance Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=25 generations
♂+♀
♀
♂
No net change under
Mendelian inheritance.
No selection for conflict
But, evolution towards
maximum sexual
conflict with maternal
effects.
39. Add + Dom Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=75 generations
♀
♂
*
Identical equilibria for
the sexes under
Mendelian inheritance.
No conflict evolves.
40. Add + Dom Intralocus Sexual Conflict
Arrow=25 generations
Space between arrows=75 generations
♀
♂
* *
Identical equilibria for
the sexes under
Mendelian inheritance.
No conflict evolves.
But, maternal effects
drives lower equilibrium
for females.
41. Add + Dom Intralocus Sexual Conflict
♂+♀
♀
♂
* * *
Arrow=25 generations
Space between arrows=75 generations
Identical equilibria for
the sexes under
Mendelian inheritance.
No conflict evolves.
But, maternal effects
drives lower equilibrium
for females.
Population equilibrium
is sub-optimal for either
sex. Conflict evolves.
43. Implications
• Sex-specific maternal allocation can drive the
evolution of sexual conflict without invoking
adaptation
• Conflict results whenever slight imbalance in
maternal allocation exists between the sexes
44. Implications
• Sex-specific maternal allocation can drive the
evolution of sexual conflict without invoking
adaptation
• Conflict results whenever slight imbalance in
maternal allocation exists between the sexes
• A simple and general mechanism of conflict
evolution with no assumptions of sex linkage
