 Large chromosomal rearrangements leading to chimeric chromosomes have been described, as well as more punctual genetic modifications such as gene loss.The homoealleles of the allotetraploid yeast "S. pastorianus" show unequal contribution to the transcriptome.Phenotypic diversification is also observed following polyploidization and/or hybridization in fungi, producing the fuel for natural selection and subsequent adaptation and speciation.