Flowering phenology in species of Chamaecrista (L.) Moench: temporal generation of functionally enantiostylous dimorphic individuals

Enantiostyly is a floral polymorphism that favours cross-pollination and genetic diversity. It is characterized by flowers with styles curved to the right or to the left. The factors that regulate the proportion and temporal dynamics of enantiostyly in monomorphic species (in which the two floral morphs occur in the same individual) are still poorly understood. This study investigated variation in morph production in four monomorphic species of Chamaecrista. We counted the number of right and left flowers from 40 individuals per species across two flowering seasons to assess daily and long-term variations in morph proportions. The species generally presented a balanced ratio of right and left flowers, regardless of the flowering period. Most individuals also showed a balanced ratio of morphs at the end of the sampling period, but their morph proportions generally changed daily. Individuals of Chamaecrista diphylla, C. rotundifolia, and C. flexuosa showed a greater number of days with unbalanced morph ratios. Chamaecrista ramosa showed no difference in the number of days in which the morphs were in similar or unbalanced proportions. Although populations with monomorphic enantiostyly exhibit a 1:1 ratio, individuals can alternate morph production, generating daily dimorphic individuals. This may hinder geitonogamy and promote intermorph cross-flow. Our results add a temporal factor to the discussion on dimorphic functionality in monomorphic enantiostylous species.