COS 76-5 - Plant polyploidy alleviates the effect of pollen limitation via floral trait differentiation

Background/Question/Methods

It is estimated that 30 % of flowering plants are polyploid, which is predicted to lead to phenotypic adaptations that increase plant reproductive success. However, there is still limited evidence of whether the polyploid origin is associated with higher reproductive success. Studies have shown that polyploidy can lead to changes in floral morphology that enhance species' reproductive success by increasing their attraction to pollinators. Thus, understanding the mechanisms by which polyploidy has shaped floral trait diversification in angiosperms and increased the reproductive success of polyploid lineages is essential to recognize their persistence in angiosperm evolutionary history. Here we use the global pollen limitation database (GloPL database) and polyploidy level estimations (i.e., polyploid vs. diploid origin) to determine whether polyploid species are less pollen limited (i.e., higher reproductive success) than diploid species. In addition, we evaluated phenotypic differences in floral traits associated with pollination attraction (corolla length, corolla width, and floral display) between ploidy levels and their relationship with the degree of pollen limitation. All our analyses were phylogenetically explicit to determine whether the increase in reproductive success of polyploids has led to their long persistence in the evolutionary history of angiosperms.

Results/Conclusions

We found that polyploid species are less pollen-limited than diploid species. Moreover, this pattern was persistent in all major angiosperm groups (i.e., Monocots, Asterids, Rosids, and Basal Angiosperms). Contrary to our expectations, polyploid species had smaller flowers and higher floral density than diploids. Further, we found a positive correlation between floral size and pollen limitation. Thus, species with small flowers that are likely to be polyploid are less pollen-limited, while species of larger flowers that are likely to be diploid are more pollen-limited. Overall, our results suggest that the high reproductive success of polyploids mediated by floral trait differentiation may explain the persistence and widespread of polyploidy through the angiosperm evolutionary history.