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Intrataxonomic trends in herbivore enamel δ13C are decoupled from ecosystem woody cover

Nature Ecology & Evolution volume 5, pages 995–1002 (2021)Cite this article

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Abstract

Analysis of enamel stable carbon isotopes (δ13Cenamel) of fossil herbivores is an important tool for making inferences about Plio-Pleistocene vegetation structure in Africa and the environmental context of hominin evolution. Many palaeoecological studies implicitly or explicitly assume that individual variation in C3–C4 plant consumption among fossil herbivores directly reflects the abundance of C3 (trees, shrubs) or C4 (low-altitude tropical grasses) vegetation. However, a strong link between δ13Cenamel of herbivores and ecosystem vegetation structure has not been rigorously established. Here we combine δ13Cenamel data from a large dataset (n = 1,643) with multidecadal Landsat estimates of C3 woody cover across 30 African ecosystems to show that there is little relationship between intrataxonomic variation in δ13Cenamel and vegetation structure. This is especially true when removing forested ecosystems (>80% woody cover)—which numerous lines of evidence suggest are rare in the Plio-Pleistocene fossil record of eastern Africa—from our analyses. Our findings stand in contrast with the common assumption that variation in herbivore δ13Cenamel values reflects changes in the relative abundance of C3–C4 vegetation. We conclude that analyses using herbivore δ13Cenamel data to shed light on the environmental context of hominin evolution should look to explicitly community-level approaches for making vegetation inferences.

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Fig. 1: Ecosystem map.
Fig. 2: Woody cover of sub-Saharan African ecosystems.
Fig. 3: Relationship between δ13Cenamel values and mean woody cover across African herbivore taxa.
Fig. 4: Distribution of woody cover in the Plio-Pleistocene fossil record and relationship between δ13Cenamel values and mean woody cover for non-forest ecosystems.

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Data availability

All data generated or analysed during this study are included in this published article (and its Supplementary Information files). Source data are provided with this paper.

Code availability

The Google Earth Engine code used can be found at: https://code.earthengine.google.com/e3e1520a7b0fcd0c26ed567f6653a9a3.

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Author information

Authors and Affiliations

  1. Archaeology Program, Boston University, Boston, MA, USA

    Joshua R. Robinson

  2. Geography–Anthropology Program, University of Southern Maine, Gorham, ME, USA

    Joshua R. Robinson

  3. Department of Anthropology, University at Albany, State University of New York, Albany, NY, USA

    John Rowan

  4. Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, Washington DC, USA

    W. Andrew Barr

  5. Department of Anthropology, University of Colorado at Boulder, Boulder, CO, USA

    Matt Sponheimer

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  3. W. Andrew Barr
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Contributions

J.R.R. and J.R. were responsible for the conceptualization of the study and writing the original draft. J.R.R., J.R. and W.A.B. were responsible for the visualization of the study. J.R.R., J.R., W.A.B., M.S. undertook the formal analysis. All authors were responsible for the methodology and contributed to and approved the final version of the manuscript.

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Correspondence to Joshua R. Robinson.

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Peer review information Nature Ecology & Evolution thanks Michaela Ecker and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data

Extended Data Fig. 1 Removing high elevation ecosystems.

Relationship between δ13Cenamel values and mean woody cover across African herbivore taxa excluding high elevation ecosystems (those spanning > 2000 m). Gray line and 95% confidence intervals show the linear fit.

Source data

Extended Data Fig. 2 Removing forested ecosystems.

Relationship between δ13Cenamel values and mean woody cover across African herbivore taxa excluding habitats with ≤80% mean woody cover. Gray line and 95% confidence intervals show the linear fit.

Source data

Extended Data Fig. 3 Proposed community approach.

Relationship between community δ13C values and mean woody cover across twenty-two African ecosystems (A). Gray line and 95% confidence intervals show linear (B) and quadratic (C) fits.

Source data

Supplementary information

Supplementary Information

Supplementary discussion, Tables 1–6 and references.

Reporting Summary

Peer Review Information

Supplementary Data 1

Recent carbon isotopic data from 30 African ecosystems used in these analyses (a subset of data from Cerling et al. 2015), and recent carbon isotopic data used for preliminary community analyses.

Source data

Source Data Fig. 1

Lat/Long data for study site locations (Statistical Source Data).

Source Data Fig. 2

Woody cover means and standard deviations (Statistical Source Data).

Source Data Fig. 3

Woody cover and carbon isotope values (Statistical Source Data).

Source Data Fig. 4

Paleosol counts (a) and slope values (b) (Statistical Source Data).

Source Data Extended Data Fig. 1

Woody cover and carbon isotope values without high elevation ecosystems (Statistical Source Data).

Source Data Extended Data Fig. 2

Woody cover and carbon isotope values without forested ecosystems (Statistical Source Data).

Source Data Extended Data Fig. 3

Community carbon isotope measure and woody cover for twenty-two modern ecosystems (Statistical Source Data).

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Robinson, J.R., Rowan, J., Barr, W.A. et al. Intrataxonomic trends in herbivore enamel δ13C are decoupled from ecosystem woody cover. Nat Ecol Evol 5, 995–1002 (2021). https://doi.org/10.1038/s41559-021-01455-7

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