Flower size dimorphism in diclinous plants native to La Reunion Island

Although many diclinous plants have a flower size dimorphism, the causes and ecological correlates of dimorphism in flower size remain poorly understood. In this paper we quantify the frequency and distribution of flower size dimorphism in the native flora of La Reunion Island. The frequency of flower size dimorphism is lower than in a previous global study suggesting that the dimorphism may limit colonisation success. Flower size dimorphism is significantly more frequent in endemic taxa compared to indigenous taxa, a trend that is particularly evident at the species level, due to the large number of species with male flowers bigger than female flowers and is more common in species-rich lineages. These results suggest that flower size dimorphism may be associated with species divergence. The direction of dimorphism varies between dioecious and monoecious species, suggesting that the mechanisms acting on flower size variation differ in species with these different sexual systems.