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

The extraordinary diversity of flowering plants has long captivated biologists andevolutionary ecologists. Plant-insect relationships are recognized as a major driverof this diversity, with pollinators playing a crucial role in angiosperm speciation andtrait diversification. Numerous observational and experimental studies have shownthat pollinators influence the evolution of floral traits—such as size, shape, color,and scent—through their preferences and selective pressures. While much of ourunderstanding of plant phenotypic diversification stems from specialized systems,most plants participate in more generalized interactions. This bias has created asignificant gap in our knowledge of how phenotypes diversify in relation topollinator communities in more generalized species. In this thesis, I investigate thedrivers of intraspecific variation in floral scent and morphology within Arabisalpina, a pollination-generalist species. Through a series of experiments, I examinethe interplay between floral traits, pollinator communities, and environmentalfactors to understand how mainly floral scent, but also plant-pollinator traitmatching,evolves across the species range. In Chapter I, I found that while floralscent shares biosynthetic links with other phytochemical traits, it may evolveindependently under pollinator-mediated selection. Chapter II demonstrated thatfloral scent emission is consistent across various conditions, despite significantdifferences in scent composition and pollinator community between neighboringpopulations. Chapter III revealed that almost all insect visitors contributeeffectively to pollination, and have variable levels of morphological trait-matching,suggesting they could influence floral trait evolution. In Chapter IV, I showed thatpollinators consistently preferred local over foreign flowers, indicating a possiblemechanism for the observed geographic variation in scent composition.Collectively, these findings suggest that floral scent variation in A. alpina is shapedby pollinator-mediated selection, potentially as a locally adapted trait. This workcontributes to the growing understanding of how floral scent as well as other floraltraits evolve in pollination-generalist species, emphasizing its significance ingeneralized plant-insect interactions.