Floral Scent in a Generalized Pollination System: Ecological Dynamics and Evolutionary Implications

The extraordinary diversity of flowering plants has long captivated biologists and
evolutionary ecologists. Plant-insect relationships are recognized as a major driver
of this diversity, with pollinators playing a crucial role in angiosperm speciation and
trait diversification. Numerous observational and experimental studies have shown
that pollinators influence the evolution of floral traits—such as size, shape, color,
and scent—through their preferences and selective pressures. While much of our
understanding of plant phenotypic diversification stems from specialized systems,
most plants participate in more generalized interactions. This bias has created a
significant gap in our knowledge of how phenotypes diversify in relation to
pollinator communities in more generalized species. In this thesis, I investigate the
drivers of intraspecific variation in floral scent and morphology within Arabis
alpina, a pollination-generalist species. Through a series of experiments, I examine
the interplay between floral traits, pollinator communities, and environmental
factors to understand how mainly floral scent, but also plant-pollinator traitmatching,
evolves across the species range. In Chapter I, I found that while floral
scent shares biosynthetic links with other phytochemical traits, it may evolve
independently under pollinator-mediated selection. Chapter II demonstrated that
floral scent emission is consistent across various conditions, despite significant
differences in scent composition and pollinator community between neighboring
populations. Chapter III revealed that almost all insect visitors contribute
effectively to pollination, and have variable levels of morphological trait-matching,
suggesting they could influence floral trait evolution. In Chapter IV, I showed that
pollinators consistently preferred local over foreign flowers, indicating a possible
mechanism for the observed geographic variation in scent composition.
Collectively, these findings suggest that floral scent variation in A. alpina is shaped
by pollinator-mediated selection, potentially as a locally adapted trait. This work
contributes to the growing understanding of how floral scent as well as other floral
traits evolve in pollination-generalist species, emphasizing its significance in
generalized plant-insect interactions.