Millennial-Scale Drivers of Small Mammal Isotopic Niche Dynamics in Southern California

41 Pages Posted: 26 May 2022

See all articles by Nathaniel S. Fox

Nathaniel S. Fox

South Dakota School of Mines and Technology

John R. Southon

University of California, Irvine

Carrie M. Howard

affiliation not provided to SSRN

Gary T. Takeuchi

affiliation not provided to SSRN

Stephany Potze

affiliation not provided to SSRN

Aisling B. Farrell

affiliation not provided to SSRN

Emily L. Lindsey

affiliation not provided to SSRN

Jessica Blois

University of California, Merced - School of Natural Resources

Abstract

Quantifying the niche of contemporary and fossil organisms is key to identifying the primary factors driving species and community dynamics through time, in particular teasing apart abiotic and biotic drivers of change. However, niche quantification can be difficult due to short time spans (for contemporary systems), time averaging (for fossil systems), and incomplete information on different aspects of ecology and environment (for both contemporary and fossil systems). Here, we use stable isotope analyses coupled with specimen-level radiocarbon dating from the Rancho La Brea Tar Pits in Los Angeles, California to examine niche dynamics over the last >55,000 years. We sampled over 100 specimens of small and mid-sized mammals, mostly sciurids (squirrels) and leporids (rabbits), from Rancho La Brea to quantify their isotopic niche, track niche changes through time, and identify probable cause(s) of those changes. Individual specimens were radiocarbon dated and niches were quantified from stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope analysis of fossil collagen to track individual isotope ecologies at precise points in time. Overall, sciurids and leporids exhibit different isotopic signals, suggesting niche variation among taxa. Comparison of animals during versus after the Pleistocene reveals differences in δ 13 C and δ 15 N values and in overall isotopic niche breadth, suggesting that small mammal resource use changed from the last glacial to current interglacial period. Evaluating the isotopic data continuously through time against a high-resolution regional climate record shows that climate contributed to small mammal niche variation over the last 55,000 years in the Los Angeles Basin. These findings reveal the complexity of long-term abiotic and biotic forcings on organismal niches and emphasize the importance of scale and data resolution when quantifying and interpreting (paleo)ecological patterns and processes.

Keywords: climate, Collagen, Fossil, Paleoecology, La Brea, Radiocarbon

Suggested Citation

Fox, Nathaniel S. and Southon, John R. and Howard, Carrie M. and Takeuchi, Gary T. and Potze, Stephany and Farrell, Aisling B. and Lindsey, Emily L. and Blois, Jessica, Millennial-Scale Drivers of Small Mammal Isotopic Niche Dynamics in Southern California. Available at SSRN: https://ssrn.com/abstract=4119786 or http://dx.doi.org/10.2139/ssrn.4119786

Nathaniel S. Fox (Contact Author)

South Dakota School of Mines and Technology ( email )

United States

John R. Southon

University of California, Irvine ( email )

Division of Nephrology, University of California I
101 City Drive South, City Tower, Suite 400-ZOT;40
Orange, CA California 92868-3217
United States

Carrie M. Howard

affiliation not provided to SSRN ( email )

No Address Available

Gary T. Takeuchi

affiliation not provided to SSRN ( email )

No Address Available

Stephany Potze

affiliation not provided to SSRN ( email )

No Address Available

Aisling B. Farrell

affiliation not provided to SSRN ( email )

No Address Available

Emily L. Lindsey

affiliation not provided to SSRN ( email )

No Address Available

Jessica Blois

University of California, Merced - School of Natural Resources ( email )

P.O. Box 2039
Merced, CA 95344
United States

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