Morphoanatomical study of Neotropical Dorstenia (Moraceae) inflorescences reveal new insights and variation in late-diverging species

Abstract

Abstract Dorstenia species are characterized by their distinctive inflorescence, the coenanthium, a fleshy discoid receptacle that contains staminate or pistillate flowers. Despite being of great importance due to the endangered status of some Dorstenia, few species have been extensively studied, leaving many aspects of their reproductive biology and evolutionary relationships unclear. This study aimed to expand our understanding of Neotropical Dorstenia species, focusing on less-explored aspects. Using light and scanning electron microscopy, we analysed the inflorescences of seven species across all Neotropical sections and conducted ancestral character reconstruction to verify the phylogenetical significance of specific traits. Results showed that aerenchyma development in pistillate flowers may play a role in fruit dispersal through ballistic ejection. Additionally, the secretory structures within the coenanthium, both external and internal, probably serve the dual purpose of attracting pollinators while also providing protection against potential damage from them, although the exact pollination syndrome remains uncertain due to conflicting data. The reproductive characteristics of the Neotropical Dorstenia differ among the three sections, with the late-diverging Emygdioa members exhibiting dioecious coenanthia, implying a transition from mixed-monoecious to dioecious inflorescences in Dorstenia.