Pollinator assemblage composition predicts trait divergence in a pollination-generalized plant

The causal role of pollinators in driving the divergence of plant traits is a fundamental tenet of angiosperm evolution, providing hallmark examples of evolution in response to natural selection. However, it remains unclear how geographic variation in pollinator assemblages relates to the divergence of pollination traits in pollination-generalized plants. We characterized pollinator assemblages that interacted with Viscaria vulgaris in southern Sweden, and evaluated, through statistical dimension reduction, whether pollination traits were associated with an inferred main axis of geographic variation in pollinator assemblages. We documented a functionally broad range of pollinators that visited V. vulgaris. Although the most frequent pollinator functional groups were present in most populations, their relative contribution to flower visitation varied across the study area, establishing a geographic mosaic of pollinator assemblages. We demonstrate that the geographic variation in pollinator assemblages can predict the divergence of pollination traits in V. vulgaris. The findings of this geographic comparative study are consistent with the hypothesis that geographic variation in pollinator assemblages drives the divergence of pollination traits in pollination-generalized plants. Thus, generalized plant-pollinator interactions do not preclude the divergence of pollination traits, which may maximize the collective contribution of local pollinator assemblages rather than that of a principal pollinator.