Evolution and development of complex floral displays

Flowering plants - angiosperms - display an astounding diversity of floral features, which have evolved in response to animal pollination and have resulted in the most species-rich plant clade. Combinations of macroscale (e.g. colour, symmetry, organ number) and microscale (e.g. cell type, tissue patterning) features often lead to highly elaborate floral displays. Most studies have focused on model species with simple floral displays to uncover the genetic and evolutionary mechanisms involved in flower evolution, yet few studies have focused on complex floral displays. Here, we review current knowledge on the development and evolution of complex floral displays. We review gene regulatory networks involved in four developmental pathways contributing to overall floral display (inflorescence architecture, organ identity, flower symmetry and flower colour) in classical plant models. We then discuss how evolutionary modification of one or more of these pathways has resulted in the production of a range of complex floral displays. Finally, we explore modular systems in which multiple pathways have been modified simultaneously, generating the most elaborate floral displays.