Although it is well established that species diversity affects the function of ecological systems, more research is needed to understand the mechanisms responsible for these effects and thus how to conserve ecological function through the management of biodiversity. This project will use laboratory experiments to investigate how the diversities of carnivores and herbivores interact to determine amount of herbivory, and how mutualisms between carnivores and herbivores can modify both predation and herbivory. Researchers will manipulate diversities of insects that eat coffee plants in southern Mexico and diversities of insects that eat them, including diversity of insect-eating ants and presence of a coffee-eating bug that ants tend for its sugary secretion. The project will test the hypotheses that diverse assemblages of herbivores are better controlled by more diverse assemblages of predators whereas only a low diversity of predators is needed to control a low diversity of herbivores, and that mutualisms between carnivores and herbivores can reduce the function of carnivore diversity as a control on herbivory.
The project will have important broader impacts on agriculture and strengthen international collaboration and the scientific workforce. Because coffee is a major crop and the project uses combinations of herbivores and predators actually found in coffee plantations, results will have immediate applications to crop production. The work builds upon a well-developed collaboration between U.S. and Mexican researchers and coffee growers. Research will help train a Ph.D. student, undergraduates, and local research assistants. Public dissemination of findings is planned through a display at the University of Michigan?s Botanical Gardens and talks at coffee plantations.
A major goal of ecological research is to understand the importance of biodiversity, the number of species, for the maintenance of the functions and processes of natural and managed ecosystems. Predator species that live in agricultural landscapes represent a valuable group of species because they often suppress pests that cause economic damage to crops. Past research indicates that one highly efficient predator species is equivalent to having multiple predator species in terms of controlling pests. However, the majority of studies to date have only tested the effects of predator diversity on single pest species and therefore overlooked the fact that crops are often attacked by more than one pest species. Much theory and empirical research suggests that having more prey species will limit the success of single predator species. Through our NSF research, we show that for diverse pest communities that attack coffee in Mexico, multiple ant predators are more efficient at suppressing pests relative to any of the single ant predator species. This suggests that in cases where there are diverse pest communities it is best to manage for multiple predator species. However, we also show that in situations with only a single pest species, having only a single predator is equivalent to having multiple predator species. Given that many agricultural crops including coffee are attacked by many economically damaging pest species, our results suggest that managing for greater predator diversity should maximize natural pest suppression. Documenting the economically valuable services provided by biodiversity is important for relating the results of biodiversity research to the general public and managers. Our research suggests managing for increased predator biodiversity my help suppress pests in coffee agriculture. Some pests of coffee can cause approximately six percent yield loss annually in the study region. This research has also provided opportunities for undergraduate research through two programs: Undergraduate Research Opportunity Program and the NSF ED-QUEST Program at the University of Michigan. Three undergraduate students and one volunteer Master’s student gained experience through the specific DDIG research projects and through research that was supported by DDIG efforts. Three of these students were from under-represented groups in the sciences. Additionally, This research provided income for field research assistants from Chiapas, Mexico near our field site a locality where few employment opportunities exist.
