Floral development of one of the oldest dioecious lineages of Arecaceae reveals different stages of dicliny in pistillate and staminate flowers.

This article focuses on the anatomical floral development of dioecious species in the Arecaceae subtribe Mauritiinae, a lineage within the Calamoideae subfamily notable for its diversity of sexual systems. Using light microscopy, the study describes the ontogeny of staminate and pistillate flowers in Lepidocaryum tenue, Mauritia flexuosa, and Mauritiella armata, identifying three key developmental phases and revealing that flowers initially form all four floral whorls before differentiating into unisexual forms. The findings suggest that Mauritiinae flowers may have evolved from a hermaphrodite ancestor, with staminate flowers showing degeneration of pistillodes and pistillate flowers retaining staminodes that produce non-viable pollen, potentially serving to attract pollinators. Overall, the floral anatomy across these species is similar, supporting their close phylogenetic relationship and indicating a transitional stage in the evolution of dicliny within this group.