Alloploids are organisms that have multiple genome sets originating from at least two parental species. Allopolyploid plants seem to have wider ecological ranges than their diploid progenitors and have the ability to exploit new habitats. Little is known about the mechanism behind this change in environmental tolerance. The alloploid plasticity hypothesis suggests that allopolyploids can maintain a high fitness in various ecological contexts by using specific adaptive gene copies or expression levels of one of the parents depending on the conditions. Studies testing this hypothesis show contradictory results. These studies typically use naturally occurring allopolyploids and the putative diploid descendants of the parent species, neglecting the fact that these may differ considerably from the true diploids parents. We intend to tackle this issue using an experimental evolution with Chlamydomonas reinhardtii. Cryopreservation will allow direct comparison of the ancestors with alloploid descendants. We plan to evolve different haploid strains in divergent stressful conditions. Once the strains show adaptation, they will be merged to obtain allodiploids. The fitness of the newly-formed alloploids will be tested in the parental stressful conditions and gene expression of the haploid and alloploid strains will be compared. We expect the alloploid to maintain a high fitness in both conditions by using either adaptive parental gene copies or expression levels.