Collaborative Research: Assessing millennial-scale community dynamics using highly-resolved mammal and vegetation food webs

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The extinction of Earth's largest animals is radically changing the feeding relationships among other species ("food webs") which may place them at greater risk of extinction in the future. This project will examine Rancho La Brea tar pits for the complete fossil record (large carnivores to plants) and build ice age food webs prior to the major changes at the end of the last ice age 12,000 years ago (human arrival, the loss of large mammals, and climate change). Understanding the relationships among ice age animals and plants will help biologists predict which species were at most risk of extinction and apply these model predictions to present-day biodiversity. This project is also an excellent opportunity to support science education and diversity, by directly involving middle school students in California and Maine in the identification of fossils used in this research. Project findings will also be shared in new La Brea Tar Pits & Museum exhibits, which draw 350,000 visitors each year. For this project, sediments from multiple asphalt seeps will be sampled for the small animals, insects and plants of the La Brea Tar Pits (California, USA). Fossils will be identified, radiocarbon dated, and then integrated into multi-trophic paleo food webs over the 40,000 years before the widespread environmental upheaval at the end of Pleistocene. Previously only the upper trophic levels (particularly carnivores) were investigated in detail; added information will test food web properties for predicting the sensitivity of species to global change. The project?s novel Bayesian framework, employed to reconstruct biomass flow, will be useful to both paleo and modern food web studies by facilitating integration of multiple proxies to characterize uncertainty in trophic interactions.