Evolution of Complex Traits: The Case ofErysimumCorolla Shape

Abstract

The evolution of flower shape has attracted the attention of biologists for at least two hundred years. Although much information is accumulating on the genetic architecture of flower shape, information on its adaptive significance is much scarcer. Using geometric morphometrics, we have explored the microevolution of corolla shape in Erysimum mediohispanicum during the past decade. We have found that, by contrast with conventional wisdom, corolla shape shows great variation even between co-occurring individuals. This variation can have strong fitness consequences, with reproductive success being associated with specific corolla shapes. Corolla shape seems to act in E. mediohispanicum as an honest signal, since it is associated with reward (nectar and pollen) and determines the preference pattern of important pollinators. Finally, since pollinator fauna varies geographically in this generalist plant species, we have detected a geographic mosaic of selection on E. mediohispanicum corolla shape in southeastern Spain that has resulted in a pattern of local adaptation. We hope that this review will encourage other evolutionary biologists to explore corolla shape microevolution, helping to unravel Darwin's “abominable mystery.”