THE MISSING PIECE II: CONSEQUENCES OF TERMINAL PLEISTOCENE MEGAFAUNAL EXTINCTION ON ECOLOGICAL INTERACTIONS BETWEEN PREDATORS AND PREY

Globally, the majority of large-bodied wild mammals are at risk. Biodiversity loss is a major conservation concern because the loss of animals also means the loss of their ecological roles within communities. Growing evidence suggests mega-mammals have a disproportionate influence on the function of modern ecosystems, although we as yet lack a comprehensive understanding of their role. Here, we use the late Pleistocene megafauna extinction as a proxy to examine the changes in the structure and ecological function of a local mammal community after the catastrophic loss of 80% of the large-bodied species on the landscape. We evaluate changes in the strength and type of mammalian associations in the Edward’s Plateau of central Texas using PAIRS analysis; the number and strength of interactions yields insights about the cohesion and resilience of ancient and modern ecosystem. We focus particularly on those interactions involving medium to large-bodied predators and their prey. The predictions from the PAIRS analysis are tested using the geochemical signal of diet derived from carbon (δ¹³C), nitrogen (δ¹⁵N), and oxygen (δ¹⁸O) analysis of bone collagen and/or bioapatite from tooth enamel for a variety of extinct and extant carnivores and herbivores (N=61 species). We find that extinct species formed significantly more species associations, and average interaction strength was also significantly stronger. Moreover, unlike modern communities, both positive (e.g., predatory-prey) and negative (e.g., competition) interactions were important before the extinction. Overall, isotopic data generally agrees with the results of the PAIRS analysis: for example, the felid guild (Panthera, Smilodon and Homotherium) are hypercarnivores and show specialization for large-bodied C4 grazers, similar to their counterparts in modern African systems. In contrast, the canids and ursids were progressively more omnivorous and fell into mixed C3-C4 to pure C3 isotopic ranges. Our results suggest that extinct carnivores were much more tightly associated with their prey base than are modern species. Thus, many fundamental aspects of mammalian communities changed with the loss of megafauna at the terminal Pleistocene.

Grant Information:

This research is supported by the National Science Foundation Division of Environmental Biology (DEB 1555525; FA Smith PI; SK Lyons and SD Newsome, co-PIs).