The evolution of novel floral organs from an evo-devo perspective

Novel floral organs represent new types of floral organs that have acquired novel identities distinct from those of the four canonical floral organs (sepals, petals, stamens, and carpels). These organs have evolved independently in multiple lineages and exhibit extensive morphological and functional diversification. However, the molecular mechanisms and ecological drivers underlying their origin and diversification remain largely unresolved in most lineages. Recent advances suggest that novel floral organs can arise through multiple developmental routes, including modification of organ identity programs, rewiring of gene regulatory networks, and elaboration of boundary regions between floral organs. In this review, we summarize these key insights and milestones by focusing on two types of novel floral organs (the staminode and corona) and one specialized floral structure (the inflated calyx). Furthermore, we propose that integrative evolutionary developmental frameworks that combine comparative morphology, functional genetics, and ecological context are therefore required to fully elucidate the origins and diversification of novel floral organs in angiosperms for future research.