Research

How do bone accumulations help us understand modern and extinct ecosystems?  Please see my page on studying Bones.


YELLOWSTONE NATIONAL PARK

Testing the ecological quality of temperate large-mammal bone assemblages

Using bones lying on the landscapes of Yellowstone National Park, I compared how well accumulations of modern skeletal remains record their source (ungulates: hoofed mammals) communities and changes in populations of constituent species over decadal-timescales. The Yellowstone bone record is highly-faithful to the Yellowstone ungulate community, capturing all native species, their relative abundance structure, and even changes in relative population sizes of individual species reaching from the last few decades to the early twentieth century.

For more, see the abstract below and my paper in PLoS ONE: "Ghosts of Yellowstone: Multi-Decadal Histories of Wildlife Populations Captured by Bones on a Modern Landscape."

Also see this press coverage: NSF, University of Chicago, University of Chicago Blog, Open Source Paleontologist, National Parks Traveler, Life Science


Proportional abundance of ungulate species in the current (2005-2007) living Yellowstone community compared with abundances in the naturally occurring bone assemblage. Bone assemblage composition is based on pooling bone counts across all transects and habitats (total MNI = 451). Error bars are bootstrapped 95% confidence intervals.  Arrows show direction of all significant population trends for species within the last decade (1995-2007; see Figure 1).  Cross denotes extirpated species (horse) with respect to the death assemblage. The ranked abundance of species in the death assemblage closely resembles the ranking of these same species in the living community (Spearman rho = 0.89, p = 0.0123). Significant live-dead mismatch is found in two native species – elk and bison – as well as in the recent invading species (mountain goat) and the extirpated species (horse).  The direction of each mismatch is correctly predicted by known population changes: recently increasing species are disproportionally rare in the death assemblage, while species with documented population declines are disproportionally abundant – the ghosts of past larger populations.

Abstract: Natural accumulations of skeletal material (death assemblages) have the potential to provide historical data on species diversity and population structure for regions lacking decades of wildlife monitoring, thereby contributing valuable baseline data for conservation and management strategies.  Previous studies of the ecological and temporal resolutions of death assemblages from terrestrial large-mammal communities, however, have largely focused on broad patterns of community composition in tropical settings.  Here, I expand the environmental sampling of large-mammal death assemblages into a temperate biome and explore more demanding assessments of ecological fidelity by testing their capacity to record past population fluctuations of individual species in the well-studied ungulate community of Yellowstone National Park (Yellowstone).  Despite dramatic ecological changes following the 1988 wildfires and 1995 wolf re-introduction, the Yellowstone death assemblage is highly faithful to the living community in species richness and community structure. These results agree with studies of tropical death assemblages and establish the broad capability of vertebrate remains to provide high-quality ecological data from disparate ecosystems and biomes.  Importantly, the Yellowstone death assemblage also correctly identifies species that changed significantly in abundance over the last 20 to ~80 years and the directions of those shifts (including local invasions and extinctions).  The relative frequency of fresh versus weathered bones for individual species is also consistent with documented trends in living population sizes.  Radiocarbon dating verifies the historical source of bones from Equus caballus (horse): a functionally extinct species.  Bone surveys are a broadly valuable tool for obtaining population trends and baseline shifts over decadal-to-centennial timescales.




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