Bandwagon effects in a floral market: early pollinator acquisition offsets colour disadvantages in less attractive flowers

Flowers with striking colours or scents are often considered to have an
advantage in the competition for pollinators. However, if pollinators copy
others to avoid exploration costs in changing environments, less
attractive flowers may benefit from acquiring early visitors by drawing
more subsequent visitors and offsetting their colour disadvantage.
Previous studies provide partial support for this view, but mostly focus
on pollinator behaviour at small spatial scales rather than on plant
benefits in the field. To investigate whether flowers benefit from
acquiring early visitors in attracting subsequent pollinator visits, we
conducted a semi-outdoor experiment in a large flight arena designed to
replicate the significant information-gathering costs encountered in field
conditions. By simulating a typical scenario where bumble bees are
motivated to shift from a flower species with declining resource quality
to newly blooming ones, we assessed the impact of early arrivals—mimicked
by dead bees placed on flowers—on subsequent pollinator attraction. When
there were no early arrivals, bees showed a preference of approximately
90% for one of the two new flower colours presented. However, when early
arrivals were placed in one of the patches, bees were strongly attracted
to the occupied patch as well as to the one with their innately preferred
colour. Notably, when their innate colour preferences and the presence of
early arrivals conflicted, the two factors either canceled each other out
or the preference was even slightly stronger for early arrivals. In other
words, floral attractiveness was the primary cue when no other bees were
present, whereas the late arrivals gave equal weight to early visitors.
This shift in bees’ foraging decisions may partly reflect changes in how
they sample new floral options. Our results suggest that less attractive
flowers may have a similar or even higher fitness than those with
attractive colouration by gaining a head start in pollinator acquisition.
This effect would be especially pronounced if the presence of conspecifics
triggers a snowball effect on the choices of subsequent foragers. The use
of social information by pollinators may thus represent an overlooked
selective force driving the evolution of early flowers, highlighting a
more multifaceted and dynamic role of pollinators in this process.