Biological Control, Biodiversity, and Multifunctionality in Coffee Agroecosystems.

Abstract

In recent decades, ecologists have come to appreciate what many farmers have long known—that biodiversity and ecological complexity play essential roles in many of the processes occurring in agroecosystems. These include many ecosystem services and functions, such as biological control, pollination, and soil fertility and preservation. At the same time, ecologically complex agroecosystems are extremely important for the maintenance of biodiversity at local and at regional scales. In short, diverse agroecosystems help to maintain biodiversity, and biodiversity helps to maintain critical functions and services in these agroecosystems. As such, it is critical to understand the role of ecological complexity in and around agroecosystems so as to maximize the benefits to the conservation of biodiversity and of ecosystem services. I focused my questions on the service of biological control and the biodiversity of natural enemies, and I performed my research on coffee farms in Mexico and Puerto Rico. First, I addressed the importance of natural enemy diversity on biological control, where I studied two ladybeetle predators of a coffee pest. I concluded that through niche partitioning, these beetles coexist and enhance overall biocontrol through species complementarity. Then, using a quantitative review, I addressed how natural enemies are influenced by ecological complexity at various scales. I found that landscape complexity may play a more important role than local heterogeneity in determining enemy abundance and diversity. Next, I focused on one natural enemy guild, parasitoid wasps, and assessed how they respond to ecological complexity at local and landscape scales. Then, through meta-analysis, I addressed the challenge of attaining farms that are both productive and that retain high levels of biocontrol. I found that win-win relationships between biocontrol and yield are probable under certain planting conditions. Finally, I take a multifunctional approach and assess how multiple taxa and multiple ecosystem services respond to ecological complexity. I found that farms can be most profitable and conserve high biodiversity if incentive structures exist to support vegetationally complex farms. In summary, my dissertation research demonstrates the importance of ecological complexity in coffee farms for biodiversity conservation and ecosystem services, such as biocontrol.