Pollinator-mediated interactions affect patterns of selection on floral traits of co-flowering plants

The importance of species interactions in shaping the evolution of ecological communities is well-established, as they can significantly alter biotic selection. Pollinator-mediated plant-plant interactions on plant reproductive performance can vary from facilitation to competition. Although richness and density of co-flowering species influences patterns of selection, the role of key species in an ecological community remains unclear. We experimentally removed flowers of a dominant flowering species, <i>Ranunculus tanguticus</i> and estimated how this dominant affected fitness components and phenotypic selection on floral traits of five neighboring species via stigmatic pollen load. <i>R</i><i>.</i><i> </i><i>tanguticus</i> had a positive effect on the pollen receipt of two plant species, <i>A. obtusiloba</i> and <i>A. souliei</i>. Correspondingly, flower attractive traits (flower height and size) rather than the mechanical-fit trait (stigma position) of both plants were subjected to significant net selection (i.e., selection differential) when <i>R. tanguticus</i> flowers were removed from the community. Moreover, two species (<i>P. fragarioides</i> and <i>T. lanceolata</i>) among the remaining three flowering plants, which exhibited neutral effects on pollen load when <i>R. tanguticus</i> was removed, experienced stronger phenotypic selection on flower size due to increased opportunities for selection. These findings show that the loss of the flowering-dominant <i>R. tanguticus</i> in alpine communities can intensify selection on floral attractive traits of co-flowering plants, independent of the nature of interspecific interactions. This highlights the evolutionary consequences of changes in community composition and biotic interactions in response to environmental shifts.