Presentation Information
[C05-05]Model of Genetic System of Lateral Asymmetry: Population Dynamics Drives Evolution of Genetic System
*Satoshi Takahashi1, Michio Hori (1. Nara Women's University (Japan))
Keywords:
Incompatibility,Lateral dimorphism,Genetic system,Oscillation,Evolution,Eco-evolutionary dynamics
Fish shows genetic lateral asymmetry, whose segregation ratio follows Mendelian without dominant lefty homozygote. This inheritance pattern can not be explained by recessive lethality. Laterality ratio in many fish species oscillates, and this laterality oscillation is presumed to be invoked by the cross predation dominance, i. e. predators feeds more on prey of the opposite laterality (cross predation) than on that of the same laterality (parallel predation).
To examine the possibility of the evolution of a genetic system that inhibits dominant lefty homozygote, we develope 1 prey 1 predator model, where both of prey and predator are diploids and have 1 locus for laterality genes, and another locus for incompatibility genes. Individuals survive or produce gametes accoding to their fitness that depends on their laterality. Incompatibility genes block fertilization of specific combinations of gamete genotypes.
Among three types of the incompatibilities, the incompatibility gene fixes only in the case of the LI-egg incompatibility, though its fraction can be positive in the other two incompatibilities. We focus on LI-egg Inompatibility. When the cross predation ratio is intermidiate (0.8) or large (0.95), the incompatibility gene increases and fix to 1.0 in the region of the predation coefficient larger than 2.0 and growth-predation ratio is smaler than 0.7. If the period of the laterality oscillation is equal to 4 years or longer, the fraction of incompatibility gene is positive, 1.0 for LI-egg incompatibility, and a genetic system without dominant lefty homozygote evolves. If the period equals 3 years or shorter, the incompatibility gene is eliminated, and a genetic system without dominant lefty homozygote never evolves.
The increase of the incompatibility gene in laterality oscillation of period 4 can be explained as follows. The lefty morph with the incompatibility gene has more righty indviduals at F2 than that without the incompatibility gene. If laterality oscillation's period is 4, the incompatibility gene tranfers between advantageous morphs (lefty or righty) at that time, better than the other allel.
To examine the possibility of the evolution of a genetic system that inhibits dominant lefty homozygote, we develope 1 prey 1 predator model, where both of prey and predator are diploids and have 1 locus for laterality genes, and another locus for incompatibility genes. Individuals survive or produce gametes accoding to their fitness that depends on their laterality. Incompatibility genes block fertilization of specific combinations of gamete genotypes.
Among three types of the incompatibilities, the incompatibility gene fixes only in the case of the LI-egg incompatibility, though its fraction can be positive in the other two incompatibilities. We focus on LI-egg Inompatibility. When the cross predation ratio is intermidiate (0.8) or large (0.95), the incompatibility gene increases and fix to 1.0 in the region of the predation coefficient larger than 2.0 and growth-predation ratio is smaler than 0.7. If the period of the laterality oscillation is equal to 4 years or longer, the fraction of incompatibility gene is positive, 1.0 for LI-egg incompatibility, and a genetic system without dominant lefty homozygote evolves. If the period equals 3 years or shorter, the incompatibility gene is eliminated, and a genetic system without dominant lefty homozygote never evolves.
The increase of the incompatibility gene in laterality oscillation of period 4 can be explained as follows. The lefty morph with the incompatibility gene has more righty indviduals at F2 than that without the incompatibility gene. If laterality oscillation's period is 4, the incompatibility gene tranfers between advantageous morphs (lefty or righty) at that time, better than the other allel.