Heterotopic evolution of the floral nectaries in Apocynaceae and their implications in the pollination

• Grant number: 18/09200-6
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): October 01, 2018
• Effective date (End): January 31, 2022
• Field of knowledge: Biological Sciences - Botany - Plant Morphology
• Principal researcher: Diego Demarco
• Grantee: Natalie Do Valle Capelli
• Home Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

When we analyze the different pollination syndromes, we find that nectar is in most cases the most important resource for plants pollinated by animals. This gives great importance to data of occurrence, position and structure of the nectaries for comparative analysis, in order to access the relationships between the different groups of plants. They can occur in all parts of the flower and produce many types of sugary exudates. Among the various plant families that have floral nectaries, Apocynaceae is distinguished by having them in different positions and with different structures and strategies for the release and storage of nectar, being a good model for the study of the evolution of this gland in relation to diversification of the family, since its phylogeny is already well resolved and sustained in relation to many of their taxa. Most species of the family have nectaries that can occur as ovarian protuberances, a receptacular ring or lobes around the ovary, possible pistillodes transformed into nectaries, or as epidermal tissue in the tube of the filaments or in the corona. In addition, the nectar can be presented on the surface of the nectary itself or transferred to corona portions that function as nectar containers (secondary presentation), being directly related to the species pollination mechanism. In order to ascertain the origin of the nectaries and their possible whorl transfer, the structure of nectaries and the floral vascularization of 32 genera belonging to the five subfamilies will be analyzed. Based on the most recent phylogenies, the reconstruction of the ancestral character states of the gland will be performed to verify in which group occurred the heterotopic alteration of the nectaries and its implication in the mechanisms of pollination. Samples to be used will come from herbarium and the material will be processed following the usual historesin inclusion techniques. In addition, the nectar of ten species belonging to the different subfamilies will be chemically analyzed to verify the metabolic changes that occurred throughout the evolution of the gland in the family. This extensive study was never carried out for the family and could bring important results to understand the diversification of the more complex flowers of the eudycotiledons and with the greater diversity of glands of the angiosperms. (AU)