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