Autopolyploids of Arabidopsis thaliana are more phenotypically plastic than their diploid progenitors.

BACKGROUND AND AIMS Polyploids are often hypothesized to have increased phenotypic plasticity compared to their diploid progenitors, but recent work suggests that the relationship between whole genome duplication (WGD) and plasticity is not so straightforward. Impacts of WGD on plasticity are moderated by other evolutionary processes in nature, which has impeded generalizations regarding the effects of WGD alone. We assessed shifts in phenotypic plasticity and mean trait values accompanying WGD, as well as the adaptive consequences of these shifts. METHODS To isolate WGD effects, we compared two diploid lineages of Arabidopsis thaliana to corresponding autotetraploids grown across different salt and nutrient conditions in a growth chamber. KEY RESULTS For the few cases in which diploids and polyploids differed in plasticity, polyploids were more plastic, consistent with hypotheses that WGD increases plasticity. Under stress, increased plasticity was often adaptive (associated with higher total seed mass) but in other cases plasticity was unrelated to fitness. Mean trait values and plasticity were equally likely to be affected by WGD, but the adaptive consequences of these shifts were often context dependent or lineage specific. For example, polyploids had extended lifespans, a shift that was adaptive in one polyploid lineage under amenable conditions but was maladaptive in the other lineage under stress. CONCLUSIONS Our work shows that increased phenotypic plasticity can result from WGD alone, independent of other evolutionary processes. We find that the effects of WGD can differ depending on the genotype of the progenitor and the environmental context. Though our experiment was limited to two genotypes of a single species, these findings support the idea that WGD can indeed increase plasticity.