Fruit and seed secondary metabolites and animal seed handling: impacts on germination success and seedling survival

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

No species can survive in isolation. Even plants, which can make their own food, depend on animals to pollinate their flowers and disperse their seeds to new sites. As the biological diversity on our planet continues to decline, it is becoming increasingly urgent to understand the interdependencies among the species that we hope to protect. The aim of this research is to deepen our understanding of interactions between plants and the seed-dispersing animals that sustain the biodiversity of tropical forests. To attract animals, plants produce fruits that are attractive and nutritious. However, fruits are much more than tasty rewards. In addition to nutrients, fruits produce natural chemical compounds that can influence the behavior and physiology of animals that consume them. For example, certain compounds in fruits have a laxative effect on animals, which could be a way for plants to influence how far the seed is transported from the parent. This research will investigate the relationships among fruit and seed chemistry, animal behavior and physiology, and seed germination and survival. This information can help scientists better protect the biodiversity of tropical forests and manage areas targeted for restoration in a way that will maximize seed germination and survival. The project will generate new educational resources on tropical forest ecology, which will be shared broadly at a local nature center and through science festivals in Virginia. Additionally, the diverse research activities in the field and lab will help train the next generation of scientists, including Latino(a) students who will be the future stewards of tropical forests in Central and South America. The project will focus on interactions between one of the most abundant and diverse groups of tropical plants - pepper plants in the genus Piper - and the animals they rely on to disperse their seeds. The most conspicuous of these animals are fruit bats, which consume fruits (and the seeds they contain) and later defecate the seeds in new sites. However, there is another group of animals that are critical to dispersal - ants. Although small, ants are the most abundant animals in tropical forests, and rapidly arrive at partially consumed fruits that are dropped by bats, or at seeds that are deposited in bat feces. Some seeds are consumed by ants, but many are removed along with pulp, moved short distances, and discarded. To assess the role of fruit and seed chemistry in determining the outcome of these interactions, researchers will conduct three experiments at La Selva Biological Station in Costa Rica. First, because nothing is known about the effects of fruit chemistry on seed-dispersing ants, they will test how fruit chemistry affects the fate of seeds removed by ants - that is, whether the seeds are consumed, cached, or discarded. This will involve experiments with captive ant colonies in which researchers can track the fate of individual seeds. Second, the researchers will investigate how handling by bats, ants, or the combination of bats and ants influences the chemistry of seeds. Third, the researchers will use seeds that have been differentially handled by bats and ants in a final experiment to determine how chemistry and animal handling influence the ultimate probability of seed germination and survival. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.