My research focuses on the ecology and evolution of interspecific interactions, particularly on the poorly-understood, mutually beneficial ones (mutualisms). Using a combination of field observations, experiments, and theory, we are examining how population processes, abiotic conditions, and the community context determine net effects of interactions for the fitness of each participant species. Specific conceptual areas of interest include: (i) conflicts of interest between mutualists and their consequences for the maintenance of beneficial outcomes; (ii) the causes and consequences of "cheating" within mutualism; (iii) context-dependent outcomes in both mutualisms and antagonisms; and (iv) anthropogenic threats to mutualisms. My recent empirical work has focused on exploited pollination mutualisms in deserts, desert grasslands, and montane habitats in Arizona and Colorado. More generally, I work towards developing a strong conceptual foundation for the very young study of mutualistic interactions.