Isotopic paleoecology of Northern Great Plains bison during the Holocene

Gaimi Davies,Fern Swenson,Blake Mccann,Igor V Ovchinnikov,Jay Sturdevant

doi:10.1038/s41598-019-52873-4

Abstract

Bison (Bison bison) are one of the few terrestrial megafauna to survive the transition into the Holocene and provide a unique opportunity to study a species on a broad spatiotemporal scale. Today, bison are primarily managed in small and isolated herds with little known about their ancestral ecology. We studied the carbon and nitrogen isotopes of Northern Great Plains bison from the terminal Pleistocene and throughout the Holocene to gain insight into their paleoecology. This time span is contemporary with the first population bottleneck experienced by bison at the end of the Pleistocene and includes the second bottleneck which occurred in the late 19th century. Results were compared with modern bison herd isotopic values from Theodore Roosevelt National Park (TRNP). Patterns of isotopic variation found in bison over time indicate significant (δ13C p = 0.0008, δ15N p = 0.002) differences in diet composition and correlate with climate throughout the Holocene. Isotopic relationships described here reveal the plasticity of ancient bison in unrestricted rangelands during periods of climatic fluctuations. Managers at TRNP and elsewhere should pursue opportunities to expand bison range to maximize forage opportunities for the species in the face of future environmental change.

Highlights

The transition from the Pleistocene into the Holocene epoch (~11.7 thousand years ago) marked the disappearance of many North American megafauna
Through conservation efforts enacted during the last century, North American bison have been brought back from the brink of extinction, but their long-term viability as a species remains threatened due to restricted rangelands, artificial selection within confined herds, and a lack of gene flow between herds
We determined that the age of ancient bison specimens range from the Late Pleistocene to the Late Holocene, 12,344 to 104 calibrated years before present with samples from the Late Pleistocene (~12.5 cal BP, n = 4), Early Holocene (11,700–8,200 cal BP, n = 1), Middle Holocene (8,200–4,200 cal BP, n = 7), and Late Holocene (4,200–100 cal BP, n = 43) (Table 2)[47]

Summary

Introduction

The transition from the Pleistocene into the Holocene epoch (~11.7 thousand years ago) marked the disappearance of many North American megafauna. In North America, the stable climate during interglaciation led to the rapid spreading of peatlands and dense forests, limiting connectivity of suitable habitat and the ability of megafauna to disperse when coping with climate change[2,7] This issue was confounded by rising sea levels that flooded former dispersal corridors[2,4]. Isotopic ratios of carbon (δ13C) and nitrogen (δ15N) are assimilated into herbivore skeletal collagen and tooth dentin through diet, recording the isotopic composition of plant material consumed[14]. These values will remain the same over time in well-preserved specimens[15]. In modern European bison, it was found that canopy cover had the biggest influence on δ15N, where less light will decrease nitrogen values in plants[29]

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Conclusion