We assessed the effects of nectar robbing on dye donation and pollen receipt in six populations (three each in 1995 and 1996) and the effects of nectar robbing on fruit and seed production and seed mass in an additional 14 populations (six in 1995 and eight in 1996).
In 1995, two of the focal plants were randomly assigned to artificial robbing treatments: one received a low level of nectar robbing (10% of available flowers robbed) and one a high level of nectar robbing (80% of available flowers robbed).
Flowers not artificially robbed were protected from natural robbing by placing a piece of translucent plastic drinking straw over the entire tubular corolla.
In 1995, we used five focal plants per population, three assigned to receive natural levels of robbing and one each assigned to the low and high robbing treatments.
In addition, we marked the calyx of all open flowers with a dot of nontoxic paint to distinguish both the week those flowers were in bloom (a different color of paint was used for each week) as well as their robbing status (robbed vs.
For naturally robbed plants in 1995, we performed a regression of average dye donation per plant on average robbing per plant to determine the relationship between natural levels of nectar robbing and dye donation.
We again employed a mixed-model repeated-measures ANOVA to examine the effects of robbing on pollen receipt per plant as well as fruit and seed production and seed mass per plant.
To examine if plants respond in a similar way to natural and artificial nectar robbing, we compared plants with similar natural and artificial robbing levels for both male and female fitness components in 1995.
Nectar robbing might have no effect on whole-plant measures of male or female function if pollinators do not discriminate between robbed and unrobbed flowers on the same plant.
On each day that the plants were in bloom, we robbed 50% of the staminate-phase flowers using the techniques described above and collared the other 50% of the flowers to prevent robbing by B.