Polyploidy and evolutionary potential

It is often assumed that polyploids possess greater evolutionary potential than their diploid progenitors because: 1) organisms with many gene copies harbor greater genetic diversity which is the fundamental substrate of evolutionary change, 2) genetic redundancy creates opportunities for duplicated genes to diverge and acquire new functions without compromising the original function, and 3) gene duplication increases the number of gene interactions, some combinations of which may enhance fitness. Thus, polyploidy may allow organisms to evolve faster or in novel directions compared to their diploid progenitors. Although this is a provocative idea and a compelling hypothesis, it has never been explicitly tested. I am testing this hypothesis in a polyploid goldenrod species. Solidago altissima.

Diploids are more genetically differentiated across environmental clines than polyploids

Populations of Solidago altissima differ in their ploidy composition across the state of Minnesota with more tetraploids in the west (gray) and hexaploids in the east (black). I hypothesized that polyploids would possess greater evolutionary potential than diploids and, therefore, would evolve more rapidly as the prairie-forest biome border shifts with climate change. However, a four-year study of these cytotypes demonstrated that diploids show strikingly greater phenotypic differentiation diploids than either tetraploids and hexaploids across latitudinal and longitudinal gradients in Minnesota (below). More clarity on this point, will be provided by a four-generation artificial selection experiment on flowering phenology where base populations of diploids and hexaploids were subjected to wet and dry conditions.