Data from: Populations with greater flexibility in floral traits modify mating system in response to the pollinator environment

1. Mixed mating and variation in outcrossing rate among populations of the
same species are common. Outcrossing can be affected by pollinator
activity and floral traits that facilitate or impede autonomous
self-fertilization. However, the relative contribution of pollen
limitation and evolved differences in the ability to self fertilize to
variation in the mating system is poorly understood and can only be
disentangled using an experimental approach. 2. We placed arrays of plants
from eight Campanula americana populations that varied in autonomous
selfing ability (hereafter "autonomy") in sun and shade habitats
to create high- and low-pollination environments. Floral visitors were
observed and pollen limitation, dichogamy, herkogamy, and pollen
persistence within the flower were measured. Outcrossing rate was
estimated for a subset of the arrays. 3. Pollen limitation was over
three-times higher in the shade than the sun due to differences in
pollinator visitation. Populations with high levels of autonomy displayed
greater pollen persistence and dichogamy in the more pollen-limited
environments than in the high-pollination environments. In these
high-autonomy populations, outcrossing rates were tightly associated with
pollen limitation, with reduced outcrossing under strong pollen
limitation. In contrast, populations with intermediate autonomy levels had
less plastic floral traits and their outcrossing rates changed little with
pollen limitation.4. Mating system was shaped by both the pollination
environment and the magnitude of plasticity in floral traits. The
experimental approach used here revealed that plasticity in floral traits
provides the ability to adjust mating system in response to limited
potential for outcrossing. The lack of plasticity in some populations
could explain mismatches between pollinator activity and mating system in
natural populations. Finally, flexibility in the mating system may help
explain the prevalence of mixed mating.