Relative demographic susceptibility does not explain the extinction chronology of Sahul's megafauna

  1. Corey J A Bradshaw  Is a corresponding author
  2. Christopher N Johnson
  3. John Llewelyn
  4. Vera Weisbecker
  5. Giovanni Strona
  6. Frédérik Saltré
  1. Flinders University, Australia
  2. University of Tasmania, Australia
  3. University of Helsinki, Finland

Abstract

The causes of Sahul's megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as eight extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.

Data availability

All data and are R code needed to reproduce the analyses are available for download at github.com/cjabradshaw/MegafaunaSusceptibility.

The following previously published data sets were used
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    13. Ulm
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    15. Bradshaw
    16. C.J.A
    (2019) FosSahul 2.0
    doi:10.1038/s41597-019-0267-3Fisher, D. O., Owens, I. P. F., and Johnson, C. N. (2001). The ecological basis of life history variation in marsupials. Ecology 82, 3531-3540. doi: 10.1890/0012-9658(2001)082[3531:TEBOLH]2.0.CO;2.

Article and author information

Author details

  1. Corey J A Bradshaw

    Global Ecology, College of Science and Engineering, Flinders University, Adelaide, Australia
    For correspondence
    corey.bradshaw@flinders.edu.au
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-5328-7741
  2. Christopher N Johnson

    Dynamics of Eco-Evolutionary Pattern, University of Tasmania, Hobart, Australia
    Competing interests
    The authors declare that no competing interests exist.
  3. John Llewelyn

    Global Ecology, College of Science and Engineering, Flinders University, Adelaide, Australia
    Competing interests
    The authors declare that no competing interests exist.
  4. Vera Weisbecker

    Global Ecology, College of Science and Engineering, Flinders University, Adelaide, Australia
    Competing interests
    The authors declare that no competing interests exist.
  5. Giovanni Strona

    Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2294-4013
  6. Frédérik Saltré

    Global Ecology, College of Science and Engineering, Flinders University, Adelaide, Australia
    Competing interests
    The authors declare that no competing interests exist.

Funding

Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CE170100015)

  • Corey J A Bradshaw
  • Christopher N Johnson
  • Vera Weisbecker

Australian Research Council (DP170103227)

  • Vera Weisbecker

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Jessica C Thompson, Yale University, United States

Publication history

  1. Received: October 9, 2020
  2. Accepted: March 29, 2021
  3. Accepted Manuscript published: March 30, 2021 (version 1)
  4. Version of Record published: April 13, 2021 (version 2)

Copyright

© 2021, Bradshaw et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Corey J A Bradshaw
  2. Christopher N Johnson
  3. John Llewelyn
  4. Vera Weisbecker
  5. Giovanni Strona
  6. Frédérik Saltré
(2021)
Relative demographic susceptibility does not explain the extinction chronology of Sahul's megafauna
eLife 10:e63870.
https://doi.org/10.7554/eLife.63870

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