In English

A model for the evolution of local adaptation of a subdivided population

anna emanuelsson
Göteborg : Chalmers tekniska högskola, 2014. 48 s.
[Examensarbete på avancerad nivå]

The ecotypes of Littorina saxatalis are believed to be intermediate steps in an ongoing speciation process. L. saxatalis is therefore of scientific interest as a model organism for speciation by local adaptation. In order to understand the genetic patterns that arise from the local adaptation, temporal and spatial adaptation dynamics in a model with two partly isolated subpopulations are analysed. The model is implemented by means of individualbased stochastic simulations and deterministic approximations. We obtain qualitative understanding of the mechanisms underlying local adaptation by investigating how a mutant allele (beneficial in one sub-population) is accepted in a system already containing two alleles (each adapted to opposite sub-populations) with frequencies in steady state. The sizes of the original alleles describe the level of local adaptation before the mutation event. We find the parameter regions where the mutant allele replaces one original allele and investigate the dynamics further within this region. We investigate the replacement probability of the mutant allele. We show that the replacement probability increases with increasing mutation effect size, decreases with increasing degree of local adaptation and decreases with increasing value of the migration rate. We investigate the improvement in average phenotype that results from a replacement of one of the original alleles by the mutant allele, and we investigate the amount of deleterious alleles within each sub-population (the gene flow). We find that the gene flow between the sub populations decrease with increased level of adaptation. By allowing for recombination between two loci, we derive results that implies that a concentrated genetic architecture is preferred by the system in certain parameter regions.

Publikationen registrerades 2015-01-30. Den ändrades senast 2015-01-30

CPL ID: 211763

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