... | ... | @@ -11,18 +11,20 @@ IBASAM included a bi-allelic (favourable-unfavourable) multilocus system for eac |
|
|
|
|
|
A genetic value (gValTrait) could be computed as:
|
|
|
|
|
|
$$ gValTrait = $$
|
|
|
$$ gValTrait = \frac{ \sum_{r=1}^{nloci} {branch1(r) + branch2(r)} }{2 \times nloci} \times RTrait + MTrait - \frac{RTrait}{2} $$
|
|
|
|
|
|
|
|
|
where *branchn(r)* was returning the locus r value (0 or 1) of the branch n, *MTrait* was the initialization mean value (at population level) and *RTrait* was the range of genetic values the trait could take.
|
|
|
|
|
|
For a trait with heritability (h^2) higher than zero, this range was computed by:
|
|
|
|
|
|
$$ RTrait = \sqrt{ \frac{VarTrait \times 2 \times nloci}{0.25 \times (1+(1−h2)/h2)}} $$
|
|
|
|
|
|
where VarTrait was the phenotypic variance of the trait.
|
|
|
|
|
|
A phenotypic value (pValTrait) of the trait was set at the initialization of the individuals following a normal distribution around the mean gValTrait and with an environmental variance (VarEnv) computed as:
|
|
|
|
|
|
$$ VarEnv = (1 − h^2) \times VarTrait $$
|
|
|
|
|
|
This genetic structure ensured that if h2 tended towards 0, pValTrait and gValTrait were equal and normally distributed around MTrait with variance VarTrait. On the contrary, if h2 was 1, the environmental variance was 0 and pValTrait was always gValTrait. To describe a trait with this structure it was only necessary to give a population mean and variance of the phenotypic value (MTrait and VarTrait) and a heritability value (h2) at start. The number of loci (nloci) was set arbitrarily to 20 for the present version of IBASAM to avoid the potential of rapid genetic drift by random fixation of alleles in the population. The genetic material of a newly born individ- ual was thus determined from that of its respective parents (see Section 2.1.7.2). For a given trait, one of the two alleles (from the two branches) at each locus was randomly chosen to make up a unique branch of code per parent. The two branches from the two parents were then transferred to the new individual to constitute its traitMap. Due to the high number of loci and the few number of generations simulated (generally <100) we considered that muta- tion was unimportant and did not implement it. However, natural selection and genetic drift were two potential evolution forces on these genetically coded traits.
|
|
|
|
... | ... | |