Mechanisms of reproductive isolation between closely related taxa play an important role in the maintenance of distinct species.  These mechanisms can be affected by paternal and maternal environmental effects on plant reproductive characteristics in potentially interbreeding plant taxa.  We examined the effects of soil nutrition, specifically phosphorous availability, on plant reproductive characteristics in two closely related species of Ipomopsis (I. aggregata and I. tenuituba) in order to determine if phosphorous availability in the paternal and maternal environment can alter pollen performance, siring success and fruit production.  We conducted greenhouse and field studies where we supplemented phosphorous levels of bolting plants and compared fruit production and pollen performance to control plants.

Results/Conclusions

Soil analyses indicate that in two replicate locations I. tenuituba grows in lower phosphorous soil conditions relative to I. aggregata. We also found an increase in pollen performance associated with phosphorous supplementation although there were no effects on female reproductive success. These paternal environmental effects on the dynamics of sexual reproduction can have a significant impact on relative siring success in hybrid crosses and influence the development of hybrid zones independently of offspring survival.