Pollination and pre-dispersal seed predation: net effects on reproduction and inflorescence characteristics in Ipomopsis aggregata.

We examined net seed production for the self-incompatible, monocarp, Ipomopsis aggregata, by monitoring pre-pollination seed parasite (Hylemya sp.) oviposition and hummingbird mediated fruit set on 21 plants of variable height. Both pollination and seed predation increased with inflorescence height. Net seed production (incorporating seed predator mortality) also was positively related to height, and this would have been the case if pollination or seed predation were doubled. Although results suggest pomopsis aggregata should be under selective pressure to maximize inflorescence height, generation time and resource limits could result in advantages for inflorescences of intermediate height.