Ecology and evolution of floral scents in the perfume flowers

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Flowers of the so-called “perfume flowers” produce floral scent that is collected exclusively by male orchid bees (Euglossini: Apidae) and used to signal their fitness/identity (species) to females during courtship display. Recent studies suggest that the evolution of floral scents in these plants is shaped by preexisting sensory biases of their euglossine pollinators. However, experimental support for this is still controversial. The chemical composition of floral scents in plants pollinated by male orchid bees, as well as their role in attracting pollinators, was intensively studied between the 1960s and 1990s. Nevertheless, current estimates suggest that pollinator identity (at the specific level) and the chemical composition of more than 80 % of all species with perfume flowers remain unknown. Obviously, the limited information about pollinators and floral scent chemistry, the unresolved phylogeny of the plant taxa involved and an incipient understanding of the sensory/behavioral biases of euglossine pollinators, make it difficult to have a more comprehensive understanding of the ecological and evolutionary mechanisms that govern the interactions between perfume flowers and their pollinators. In the present proposal, we aim at understanding the ecological and evolutionary meaning of floral perfumes. For this, we will use modern techniques from various disciplines, such as chemical ecology, pollination biology, behavioral ecology, insect physiology and molecular phylogeny. Current knowledge about pollinators and about the chemical composition of floral perfumes will be compiled in a systematic review of the literature. In order to add to the knowledge of the interactions, floral visitors will be collected directly on flowers. The floral scent samples will be collected and used for bioassays and chemical analyses. Sensory (olfactory) biases of pollinators will be investigated using electroantenographic (EAG) analyzes, and behavioral bioassays in the field will be performed with male orchid bees. The phylogenetic relationships of species with perfume flowers, as well as their pollinators will be reconstructed based on molecular data available in GenBank. With this integrative approach, we will test fundamental hypotheses about the macroevolution of floral attributes in perfume flowers as a whole. In view of its multidisciplinary approach, this project will involve an experienced team of researchers from different institutions, promoting the strengthening of well-established and successful international cooperation and the exchange of students. This project will help us to both contribute to the scanty knowledge on basic aspects of the natural history of the specialized interaction involving male orchid bees and perfume flowers and understand the significance of floral scents in the ecology and evolution of this mutualism.