Chemical Coevolution of Animals and Plants

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To promote seed dispersal, fleshy fruits evolved to attract animals using various adaptations like sugary rewards and colorful displays. Animals evolved to exploit fleshy fruits using adaptations such as attraction to sugar and color vision. In recent years, our work provided evidence that fruit scent - the bouquet of volatile chemicals emitted by ripe fruits - is likely to be a signal whose function is to facilitate seed dispersal, as opposed to a pleasant byproduct of fruit maturation. Moreover, we identified chemicals which are likely to derive from sugar and thus be the substrate on which chemical communication between animals and plants has evolved. Yet these observations are still based on ecological snapshots, and it is therefore unknown whether plants have indeed evolved to signal ripeness through chemical signals. Moreover, given that before this work the chemistry of wild ripe fruit scent was almost unknown, it is unknown whether seed dispersers’ sense of smell evolved to utilize fruit chemical signals. As a result, while it is known that fruit traits drive plant dispersal, speciation and diversification, the role of chemical communication - a critical factor in animal-plant interaction - in driving plant and animal coevolution has remained in the dark. Using figs and lemurs as a model systems, the proposed project will address these questions in three units. The first will use ecological, chemical, genetic and transcriptomic approaches to establish that fruit scent has evolved as an honest signal to seed dispersers. The second will use comparative physiology to establish that fruit-eating animals are selected to respond to the chemicals plants use as signals. The third unit will use a phylogenetic approach to establish how chemical communication has driven plant biogeography. As such, the project will study how animals and plants have co-evolved to communicate using chemical signals, and how this process drove plant evolution in space and time.