Over the past 35 years, a robust theory of plant defenses has been developed to explain why plant species vary in the toxicity and physical toughness of their vegetative tissues. Application of this theory has broadened our understanding of plant-herbivore interactions, yielding new insights into plant ecology and evolution. This project will now extend the theory to cover defenses of seeds against fungi in the soil. Seeds have only a limited capacity to adjust resource acquisition and allocation to track a changing environment or to combat individual threats. Fungi that attack and can kill seeds should therefore create strong selection on suites of characteristics, or seed defense syndromes. This project will quantify the chemical and physical defenses of seeds of 18 tree species that exhibit a broad range of seed traits and germination behavior in lowland tropical forest in Panama. Experiments will determine the time course of seed survival, the efficacy of defenses at different times following dispersal onto the soil, and the ways in which particular defenses correlate with others to form syndromes of seed defensive traits. The study will offer a new perspective on the ecological and evolutionary importance of seed dormancy and a first step towards formalizing seed defense syndromes for an array of ecologically important plants.
The project will provide unique, cross-disciplinary training in tropical ecology, molecular biology, and fungal biology at the undergraduate, graduate, and post-doctoral levels and will support research and publication by students from the United States and Latin America. Research protocols and data sets will be posted on a bilingual, project website, and results will be disseminated through the public outreach programs of the Mycological Herbarium of the University of Arizona.