LTREB Renewal: Climatic drivers of temporal and spatial dynamics of a focal herbivore

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The Earth's climate has changed continually over 4 billion years. The recent increased pace and direction of this change challenge the nation's welfare, the economics of agriculture, and the management of essential resources. This project provides a unique opportunity to identify the mechanisms by which short-term climatic effects cause long-term population changes, affect spatial exchanges between local populations, and result in the extinction of some populations. The project focuses on a common herbivore, the wooly-bear caterpillar, and results have the potential to inform conservation and management of beneficial as well as pest herbivores. More importantly, the project will be integrated into high school curricula by involving students and teachers in monitoring caterpillar abundances. Undergraduate students from groups under-represented in science and graduate students will also receive training in the practice of science through their participation in the project The wooly-bear moth, Platyprepia virginalis, is a primary herbivore on lupines in California. The investigators have accumulated up to 30 years of abundance data for this species and for important drivers of its population dynamics, including host plants, other herbivores, predators, parasitoids, movement, and climatic conditions. The project will initiate short-term experiments to identify mechanisms that causally link climatic factors to observed patterns of abundance and distribution across habitats. These will evaluate top-down effects of climate on predators, bottom-up climate effects through a facilitative interaction involving a second herbivore species, and the effects of flooding and litter accumulation on caterpillar vital rates. Statistical analyses and mathematical models will test inferences from these experiments, evaluating whether the hypothesized mechanisms cause inter-annual fluctuations in abundance and changing spatial dynamics including local extinctions. The project's combination of manipulative experiments with model development and analyses of long-term demographic data is rare. It will provide a well-documented example of source-sink dynamics, an ecological phenomenon for which data remain scarce, and is likely to become a classic example of the consequences of climate change for population dynamics.