Polyploid species possess more than two sets of chromosomes and may show high gene redundancy, hybrid vigor and masking of deleterious alleles compared to their parent species. Following this, it is hypothesized that this makes them better at adapting to novel environments than their parent species, possibly due to phenotypic plasticity. The allopolyploid Arabidopsis suecica and its parent species A. arenosa and A. thaliana were chosen as a model system to investigate relationships between phenotypic plasticity, fitness and genetic variation. Particularly, we test if A. suecica is more plastic, show higher genetic diversity and/or have higher fitness than its parent species. Wild Norwegian populations of each species were analyzed for phenotypic responses to differences in availability of nutrient, water and light, while genetic diversity was assessed through analysis of AFLP markers. Arabidopsis arenosa showed a higher level of phenotypic plasticity and higher levels of genetic diversity than the two other species, probably related to its outbreeding reproduction strategy. Furthermore, a general positive relationship between genetic diversity and phenotypic plasticity was found. Low genetic diversity were found in the inbreeding A. thaliana. Geographic spacing of populations might explain the clear genetic structure in A. arenosa, while the lack of structure in A. suecica could be due to coherent populations. Fitness measured as allocation of resources to reproduction, pointed towards A. arenosa having lower fitness under poor environmental conditions. Arabidopsis suecica, on the other hand, showed tendencies towards keeping up fitness under different environmental conditions.

These data were generated to investigate phenotypic and genetic differences in the allopolyploid species Arabidopsis arenosa Arabidopsis suecica (Fr.) Norrl. ex O.E.Schulz and its two parent species, A. thaliana (L.) Heynh. and A. arenosa (L.) Lawalrée. Wild Norwegian populations of each species were analyzed for phenotypic responses to differences in availability of nutrient, water and light, while genetic diversity was assessed through analysis of AFLP markers.