The molecular and evolutionary basis of dichogamous reproductive strategies in flowering plants

Dichogamy, a reproductive strategy in plants, describes the temporal separation of maturation between female and male reproductive organs within a flower or across flowers. Under similar environmental conditions, dichogamous species exhibit asynchronous development of their sexual organs during flowering, rather than morphological divergence. This phenomenon is classified into protandry (male-first maturation) and protogyny (female-first maturation) on the basis of the maturation sequence, into intrafloral or interfloral dichogamy on the basis of the spatial scope, and into complete or incomplete dichogamy depending on the degree of separation. Further subdivisions include synchronous or asynchronous types, determined by the synchronicity of sexual maturation within individual plants. Studies reveal that dichogamy arises from a dynamic equilibrium shaped by direct and indirect interactions of multiple factors. Biotic drivers, such as pollinators' behavior, promote co-evolutionary dynamics, while abiotic factors indirectly regulate key genes governing the timing of flowering, thereby modulating dichogamy. Hormonal signaling pathways critically regulate floral development and sexual differentiation, and epigenetic mechanisms, including DNA methylation and histone modifications, further fine-tune these processes. By temporally and spatially isolating sexual functions, dichogamy reduces selfing risks, enhances outcrossing, enriches genetic diversity, and underpins the breeding of high-yield, genetically diverse hybrids. However, this strategy entails trade-offs, such as resource allocation conflicts and restricted gene flow. The diverse ecological manifestations of dichogamy reflect its adaptive significance as a key driver in the evolution of plants' reproductive strategies. This review systematically examines the mechanistic basis, regulatory factors, and ecological implications of dichogamy, offering insights into its role in plant reproduction, biodiversity, and hybrid breeding.