Fruits provide a direct link between parent plants and their offspring and are thus key determinants of plant reproductive success. A primary function of fleshy fruits is to attract animal seed dispersers; however, the same nutritional rewards that attract mutualists may also attract diverse antagonistic consumers, such as vertebrate and invertebrate seed predators and microbial pathogens. One important way that plants mediate the complex multi-species interactions surrounding fruits is through the production of secondary metabolites in fruit flesh. Increasing evidence has shown that secondary metabolites can influence multiple pre- and post-dispersal processes involving both mutualistic and antagonistic consumers. This talk will review the numerous functions of secondary metabolites in fleshy fruits, using examples from six years of research focused on the chemical ecology of seed dispersal and fruit defense in the tropical plant genus Piper.
Results/Conclusions
Fruit secondary metabolites in Piper are abundant and structurally diverse. Complex blends of volatile metabolites provide foraging cues that allow the primary dispersers of Piper fruit, bats in the genus Carollia, to locate ripe fruits in complex biotic environments. Other non-volatile Piper fruit metabolites, such as amides, function primarily in fruit defense against both insect seed predators and fungal pathogens. However, these same defensive metabolites can also have complex implications for interactions with mutualist bats. Amides affect multiple aspects of bat foraging and feeding behavior, reducing overall fruit consumption and likely leading to fitness trade-offs between seed dispersal and fruit defense. They can also affect bat digestive physiology, causing seeds to pass more quickly through bat guts and leading to complex changes in the dispersal patterns of seeds. Our ongoing work seeks to characterize these and other aspects of the complex chemical ecology of fruit/frugivore interactions in this system, providing a compelling example of the importance of fruit chemical traits in plant reproductive success.