Pollinator-mediated selection is an important mechanism in the evolution of floral traits. Theory predicts that there will be less phenotypic variation and high phenotypic integration in specialized plant pollinator systems. Selection will also favor specific floral traits that impact fitness directly. In this study, we examine the role of pollinator-mediated selection on the evolution of floral traits in twenty sympatric Ipomoea species by comparing the phenotypic variances and integration parameters (measured as the variance of the eigenvalues of a correlation matrix through a PCA) of floral traits in species that differ in their pollination system (i.e. specialized vs. generalized pollination system).
Results/Conclusions Plants pollinated by exclusively one functional group show less phenotypic variation (mainly on tube length and corolla length) and higher floral integration than plants pollinated by more than one functional group. Our results also show that traits related to pollination effectiveness show less variation and greater floral integration than traits exclusively related to pollinator attraction. These results suggest that plants with specialized pollination experience strong selective pressures on floral traits than plants with generalized pollination. In addition, these results are consistent with the idea that pollinator-mediated selection promotes intrafloral integration rather than integration of the whole flower.
