Revisiting the inflorescence structure, the floral traits and pollen aggregations of four species of Mimosa (Leguminosae, Caesalpinioideae) occurring in Mexico

Background: With 615 species worldwide, Mimosa is among the largest genera of the Leguminosae family, and Mexico is the second center of distribution of the genus after Brazil, with 105 species. In recent years, interest has arisen in morphological and anatomical characters of the flower in relation to floral visitors in Mimosa. Questions: What is the relationship between inflorescence type, number and arrangement of flowers on the floral axis? What are the morphological and anatomical characters of the floral whorls that distinguish the Mimosa species? Which is the pollen-stigma relationship, how does it influence the reproductive strategies? Study species: Por favor cambiar a: Mimosa affinis B.L.Rob., M. albida Humb. & Bonpl. ex Willd., M. lactiflua Delile ex Benth., and M. polyantha Benth. Study area: Southeastern Morelos and southwestern Puebla, Mexico. Methods: A comparative study of inflorescence morphometry in capitula and spikes was carried out, to evaluate the merism variability of flowers in anthesis, the comparative morphoanatomy of flowers and pollen aggregations. Results: Statistical analysis showed differences in morphometric characters of inflorescence, flower and pollen aggregation. There are anatomical differences in the flowers such as: various types of trichomes on the bracteole, perianth and ovary; fusion of the stamens at the base; poriform and crateriform stigma; paracytic stomata; striate cuticle in epidermal cells. Conclusions: The species showed morphological and anatomical differences in inflorescence, flower and pollen aggregation, generating relevant information to understand Mimosa’s reproductive strategies although further studies of floral characters are needed regarding the interactions with floral visitors.