Evolution of increased vigour associated with allopolyploidization in the newly formed invasive species Salsola ryanii

AbstractA correlation between allopolyploidization and increased fitness is an explanation for the importance of allopolyploidy throughout evolution, specifically plant evolution. Although many authors have suggested correlation between allopolyploidy and increased fitness, common garden comparisons testing hypotheses about fitness shifts associated with allopolyploidy are lacking. In this study, we test the theory that allopolyploidy is associated with increased fitness in the newly formed allopolyploid weed Salsola ryanii. We conducted a common garden comparison over 2 years to determine how different fitness correlates (plant volume, plant mass and estimated seed number) of the newly formed allopolyploid species S. ryanii compares to its progenitors (S. tragus and S. australis) at a site within the range of all the newly formed allopolyploid and both of its progenitors. We document an increase in above-ground plant mass and above-ground volume in the newly formed allopolyploid compared to its progenitors. Plant mass and volume of the newly formed allopolyploid relative to its progenitors was dependent on year. The results of this study support the hypothesis that allopolyploidization is associated with increased growth, which is consistent with predictions that allopolyploid lineages experience vigour due to fixed heterozygosity.