EAGER: The relative contributions of pollen and seed dispersal to gene flow and propagule survival in a tropical palm

Tulane University, New Orleans LA

Investigators

Abstract

Many plants rely on animals to pollinate their flowers and disperse their seeds. These services are important because most plants are literally rooted in place, with animals providing one of their only opportunities to colonize new places. Ecologists are especially interested in the relative importance of seed dispersal and pollination. If, for example, seed dispersal is more important than pollination, then declines in seed disperser populations will have greater ecological impacts than declines in pollinators. This project will use genetic techniques and field experiments to test the impact of pollinators and seed dispersers on the ability of a tropical tree to grow and survive under conditions near and far from parent trees of the same species. The researchers will integrate their work with education and sustainable development programs that are designed to improve conservation outcomes in the study area, a biodiversity hotspot in Ecuador. The project will provide training for undergraduates, graduate students and post-doctoral fellows, and will use public presentations, websites, film and video to communicate results to the public. The study design combines correlative data from the field with experiments and molecular analyses to address how seed dispersal mediates the initial pattern of gene flow achieved by pollination and to investigate how patterns of mortality shape the relative contribution of pollen vs. seed dispersal at successive life stages. The particular focus is on how genetic 'uniqueness' of a dispersed seed (i.e., the seed's genotype relative to the existing genetic background of all other seeds nearby) may influence its survival. The study system is an animal-dispersed tropical palm, Oenocarpus bataua, in northwest Ecuador. The working hypotheses are that: (1) long distance seed dispersal will promote gene flow by introducing novel male gametic genotypes into seed pools; (2) after controlling for dispersal distance and density, genetic uniqueness will be associated with increased seed and seedling survival; and, (3) the relative contribution of seed dispersal to realized gene flow will increase across successive life stages. Dispersal kernels will be calculated for both pollen and seeds via molecular analyses. Survival of naturally dispersed seeds will be analyzed in relation to dispersal distance, conspecific density, and genetic uniqueness. A complementary, field-based reciprocal transplant experiment will manipulate genetic uniqueness and dispersal distance of seeds, then provide data on subsequent growth and survival of seedlings. Finally, genetic structure will be compared across multiple age classes, from seed to adult. Many students will be mentored in research. Results will be disseminated through a blog and a YouTube channel, and incorporated into a field course.