Collaborative Research: Moving beyond causation: the ecological consequences of the terminal Pleistocene extinction of North American megafauna

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Biodiversity is being lost from ecosystems worldwide, and when it results in the loss of large-bodied species (megafauna) it can have major consequences for entire food webs, and the structure and function of those ecosystems. This study will examine a past major extinction of megafauna in order to understand the cascading effects on ecosystems. About 13,000 years ago many species of large mammals in the Americas became extinct. This research will examine the consequences of the loss of these large carnivores and herbivores from the food web to the remaining plant and animal communities. The responses seen at this long-ago event will be used to develop general concepts relevant to modern-day changes in plant and animal communities. This project will also make fossil data more easily accessible and interpretable, will improve museum collections, and will inform the public through outreach activities conducted by the Smithsonian Institution. This work will also provide graduate and undergraduate students with research experience that will strengthen the scientific workforce. The consequences of the loss of tens of millions of large-bodied mammals about 13,000 years ago on the structure and functioning of ecosystems in the Americas will be examined in order to address four questions: How did the extinction of large-bodied mammals influence overall community structure and species interactions at the terminal Pleistocene; Did surviving species become more abundant or change their geographic distribution; What changes in morphology, if any, occurred in species that survived the extinction; Did surviving species alter their dietary niche in response to the extinction of megafauna? Patterns of abundance, distribution, diet and morphology in the surviving mammals both before and after the extinction event will be characterized. Using occurrence information from fossil database compilations, morphology and size will be determined by measuring fossil limbs and molars, and diet by using stable isotope analysis. These data will be integrated with reconstructions of vegetative communities using pollen databases and regional and global temperature records. An important ecological baseline for the understanding of contemporary trophic downgrading will be established by characterizing how terrestrial ecosystems were influenced by humans at an important point in human history.