Selfing in haploid plants and efficacy of selection: codon usage bias in the model moss Physcomitrella patens

Genome Biol Evol.         online article

Physcomitrella patens constantly undergoes self-fertilization, a mechanism considerably reducing its effective population size. The effects of this reduction are predicted to be much more dramatic on haploid-selfing organisms, such as P. patens, than on diploids. By analyzing synonymous codon usage bias of Physcomitrella genes, we provide evidence for the predominant role of genetic drift and only very weak effect of natural selection. While these findings are in contrast to a previous study they are in line with population genetic theory.