Extinctions and keystone species

Duncan Golicher

Recent loss of keystone species

Are we witnessing the sixth mass extinction?

How do we compare current extinction to the past?

What is the background rate?

Recent extinctions

Which species are becoming extinct?

Why might extinctions on islands have a greater impact on their ecosystems?

Extinctions on continents

Extinction of keystone species on continents

When did the extinction of keystone species occur on continents?

What caused the extinctions?

Arguments against climate change as main driver

Climate of last 5 million years

Arguments against disease hypothesis

Arguments against hunting

Ecological arguments in favour of hunting (overkill) hypothesis

Hunted to extinction?

Large mammals became extinct

(Lyons, Smith, and Brown 2004)

Large mammals became extinct

Carbon dioxide levels

Low CO2 point 35 thousand years ago

Summary of late quaternary extinctions

Consequences

Mastodon

Evidence for vegetation change

Evidence for increase in deciduous trees

(Gill 2013)

Possible consequences

Possible consequences

The Vera hypothesis

(Hitchmough and Vera 2002)

References

“Atmospheric CO 2 Concentrations over the Last Glacial Termination.” 2001. Science 291 (5501): 112–14. https://doi.org/10.1126/science.291.5501.112.
Boehm, Mannfred M. A., and Quentin C. B. Cronk. 2021. “Dark Extinction: The Problem of Unknown Historical Extinctions.” Biology Letters 17 (3). https://doi.org/10.1098/rsbl.2021.0007.
Gill, Jacquelyn L. 2013. “Ecological Impacts of the Late Quaternary Megaherbivore Extinctions.” New Phytologist 201 (4): 1163–69. https://doi.org/10.1111/nph.12576.
Hitchmough, James, and F. W. M. Vera. 2002. “Grazing Ecology and Forest History.” Garden History 30 (2): 263. https://doi.org/10.2307/1587257.
Lamkin, Megan, and Arnold I. Miller. 2016. “On the Challenge of Comparing Contemporary and Deep-Time Biological-Extinction Rates.” BioScience 66 (9): 785–89. https://doi.org/10.1093/biosci/biw088.
Lyons, S. Kathleen, Felisa A. Smith, and James H. Brown. 2004. “Of Mice, Mastodons and Men: Human-Mediated Extinctions on Four Continents.” Evolutionary Ecology Research 6: 339–58.
Pimm, S. L., C. N. Jenkins, R. Abell, T. M. Brooks, J. L. Gittleman, L. N. Joppa, P. H. Raven, C. M. Roberts, and J. O. Sexton. 2014. “The Biodiversity of Species and Their Rates of Extinction, Distribution, and Protection.” Science 344 (6187). https://doi.org/10.1126/science.1246752.