In nature, ecosystem function varies extensively across space. Some ecosystems are extremely diverse while others support only a few species. Ecological theory suggests that dispersal of individuals across space is critical to the persistence of functional ecosystems and predicts that, at some intermediate level of dispersal, individuals can colonize favorable habitat patches and maintain functional ecosystems. The proposed research will be the first to test these theoretical predictions in complex communities. Researchers will construct communities of micro-organisms in laboratory petri dishes to implement a robust experimental design that includes patches of favorable and unfavorable habitats and that measures multiple ecosystem functions (productivity, respiration, abundance). In these controlled microcosms, the researchers can impose a wide range of dispersal levels. The experiments incorporate the complexity common in natural communities, will test the importance of dispersal and sorting dynamics, and will produce data necessary to revise existing theory.
Humans are causing major changes to the movement of organisms across ecosystems. Some ecosystems are declining in connectivity through the fragmentation of habitat, while others are becoming more connected under increased rates of trade and habitat homogenization. Understanding the impacts of these changes on biodiversity and the provisioning of ecosystem services requires the robust testing of ecological theory. In parallel, the research will inform pest control and conservation in agro-ecosystems. The co-PI plans interactive lectures in Austin public schools to link science with management and will train undergraduate students in all aspects of his research. Finally, the experiments are part of a strong international collaboration among eight researchers who study metacommunity ecology from different perspectives.
We implemented an experiment testing spatial ecological theory using aquatic microbial microcosms. The experiment was aimed at testing the combined effects of dispersal and disturbance on the matching between species and their optimal environments, food webs, and ecosystem function. This was accomplished by manipulating the rate at which patches were destroyed in landscapes with low levels of dispersal. Disturbance events coupled with low levels of dispersal are found in many real-world landscapes. Humans are dramatically reducing connectivity in many landscapes, resulting in the decline and collapse of food webs and ecosystem services like the biological control of agricultural pests. In addition, disturbance events are becoming more frequent with climate change. We found that predators play a critical role in controlling the matching between prey and their optimal environments. In landscapes without disturbance, predators are the most important determinant of the distribution of the prey. This is because predators both consume prey at a local scale and influence regional dynamics by affecting the dispersal rate of the prey. In landscapes with disturbance, predators are far less important. This is because predators are highly susceptible to disturbance because their small population sizes and fluctuating populations. These results have produced one conference publication and two manuscripts are currently in preparation. This experiment also forged a collaboration between the University of Texas and the National Institute of Environmental Studies in Japan. Finally, these results suggest that even in the absence of any change to the background environment, disturbance events can have major effects on ecosystems by disrupting the adaptive match between species and their optimal environments.
