THE INFLUENCE OF THE TERMINAL PLEISTOCENE EXTINCTION ON ECOLOGICAL COMPLEXITY AND PREDATOR PREY INTERACTIONS WITHIN A MAMMAL COMMUNITY

Modern trophic downgrading is leading to changes in the ecological interactions within communities. For carnivores, in particular, the loss of apex species may have a cascade of effects. Here, we use the fossil record of the terminal Pleistocene to explore the consequences of past trophic downgrading. We characterize both the isotopic and body-size niche of a mammal community in Texas before and after the event to assess the influence on the ecology and ecological interactions of surviving species (>1kg). Pre-extinction, a variety of C4-grazers, C3-browsers, and mixed-feeders existed, similar to modern African savannas, with likely specialization among the apex carnivores (two sabertooth cats) for juvenile grazers. Post-extinction, body size and isotopic niche space were lost, and the δ13C and δ15N values of some survivors shifted. We see mesocarnivore release within the Felidae: the jaguar, now an apex carnivore, moved into the specialized isotopic niche previously occupied by extinct cats. Puma, previously absent, became common and lynx shifted towards consuming more C4-based resources. In contrast, we observe little changes in diet or body size among the surviving Canidae. Overall, considerable ecological complexity was lost in the Holocene community. Our results suggest that the impact of trophic downgrading on communities may be taxonomically specific.