Pollen Competition Improves Performance and Reproductive Output of the Common Zucchini Squash Under Field Conditions

The objective of this study was to examine the effects of pollen competition on offspring quality in the common zucchini squash ( Cucurbita pepo L.). In a controlled field study, we compared the performance of seeds that were produced under conditions of pollen competition (high pollen loads) to seeds produced under conditions of little or no pollen competition (low pollen loads). We found that seeds from high pollen loads were more likely to emerge and emerge more rapidly than seeds from low pollen loads. The high pollen load seedlings also tended to produce more flowers and fruits than the low pollen load seedlings. On a per-plant basis, the high pollen load progeny had significantly greater fruit volume, seed numbers, and total seed weight than the low pollen load progeny. We conclude that in zucchini, seeds produced under conditions of pollen competition are “superior” to seeds produced when pollen competition is minimal or absent. The significance of these results is considered in light of a previous study revealing nonrandom patterns of fruit abortion in this species.