Multiple aspects of the selfing syndrome of the morning glory Ipomoea lacunosa evolved in response to selection: a Qst-Fst comparison

The frequent transition from outcrossing to selfing in flowering plants is often accompanied by changes in multiple aspects of floral morphology, termed the “selfing syndrome.” While the repeated evolution of these changes suggests a role for natural selection, genetic drift may also be responsible. To determine whether selection or drift shaped different aspects of the pollination syndrome and mating system in the highly selfing morning glory Ipomoea lacunosa, we performed multivariate and univariate Qst-Fst comparisons using a wide sample of populations of I. lacunosa and its mixed-mating sister species I. cordatotriloba. The two species differ in early growth, floral display, inflorescence, corolla size, nectar, and pollen number. Our analyses support a role for natural selection driving trait divergence, specifically in corolla size and nectar traits, but not in early growth, display size, inflorescence size, or pollen traits. We also find evidence of selection for reduced herkogamy...