The ecology and evolution of mutualism

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Understanding how cooperation evolves despite selection for "cheating" is a central problem in evolutionary biology. The evolution of cooperation between species, or mutualism, is especially perplexing because partners do not share genes, precluding inclusive fitness benefits. Yet mutualisms are common, diverse, and often ancient, and they have important consequences for biodiversity and ecosystem functioning. The long-term objectives of my research program are: 1) to test, complement, and extend theory on the evolution of cooperation to understand how mutualisms and other forms of cooperation persist despite the "temptation to cheat," and 2) to look beyond cheating to broadly characterize the ecological and evolutionary dynamics of mutualisms. This grant addresses four fundamental questions about mutualism ecology and evolution: 1) What traits select for cooperation between species, preventing exploitation by cheaters, and how do these traits evolve? 2) How does a candidate gene modulate mutualist quality in a classic plant-animal mutualism? 3) Does mutualism generate positive feedback between co-introduced species that facilitates biological invasions? And 4) how do multiple animal mutualists collectively exert selection on plant traits? To answer these questions, my students and I will couple experimental methods with molecular and quantitative genetic analyses in diverse systems, including legume-rhizobium, ant-plant, pollination, and seed dispersal mutualisms. This research will improve our understanding of how partners in mutualisms coevolve, the role of mutualism in shaping trait evolution, the consequences of mutualisms for the ecological communities in which they are embedded, and mutualisms as drivers of ecological change. It will also provide high-caliber students and postdoctoral fellows with broad training in ecology and evolutionary biology, especially in how to conduct rigorous, manipulative field and greenhouse experiments, as well as in several branches of genetics and in theory on the evolution of cooperation. This integrative approach encourages the intellectual development of advanced undergraduates, graduate students, and postdoctoral fellows, and will prepare them for careers in basic and applied research environments.