2.3.2 Seed production
We used seed production per fruit as a proxy for the female component of plant reproductive success. Flowers on inflorescences received a daily three-hour ‘window’ of pollination by natural bumblebee visitation for the entirety of their flowering period. After the flowering had finished, we left plants unbagged to allow fruits to develop normally. Around 4-6 weeks after flowering, we collected between three and seven near ripe but undehisced fruits from each plant at various points on the inflorescence and then left them to dry inside paper envelopes to allow natural dehiscence of fruits. We photographed seeds on filter paper and then counted using a macro in ImageJ software.
Statistical Analyses
Visitation rates (visits per flower per hour) were compared between robbed and non-robbed plants using generalised linear models with a binomial distribution (flowers visited vs not visited) in thestats package in R (R Core Team, 2020). We included the pollinator as a fixed factor in the model to test for differences between the two bumblebee species, and a term for the interaction between treatment and pollinator.
The duration of a visit to a flower was compared between robbed and non-robbed plants using linear models in R, where visit duration was log-transformed. We included pollinator as a fixed variable in the model, to test for differences in visitation by the two species, and for whether there was an interactive effect of treatment and pollinator.
We tested for differences between control and robbed treatment plants for the proportions of flowers visited (with pollinator species included as a fixed factor) and the proportion of rejections using generalised linear models with a binomial distribution in the stats package in R.
We compared pollen export between the robbed and control treatments using mixed effects linear models in R, with plant individual as a random factor (packages lme4 and lmerTest, Bates et al ., 2015). We used the same approach to compare the number of seeds produced per fruit between the treatments.
Results