Functional significance of pollen size variation in ipomoea purpurea, common morning glory: small pollen size leads to siring advantage under natural pollination

Variation in pollen size is present in Ipomoea purpurea, common morning glory, and this study looks at its functional role. Based on the findings in previous studies, we hypothesize that large pollen grains have a siring advantage over small pollen grains in a pollination setting that is natural for the species. We found that small pollen grains sire more seeds than large pollen grains, suggesting that small pollen grains have a mechanism to overcome their disadvantage when in direct competition with large pollen grains. However, small pollen plants and large pollen plants did not significantly differ in terms of overall fitness, implying that large pollen plants produce more seeds than small pollen plants. Future work will need to focus on the mechanisms that small pollen plants utilize in order to sire more seeds than large pollen plants.