A New Look at the Major Features of Evolution

Stevan J. ArnoldDepartment of Integrative Biology

Oregon State University

Outline

• Criteria for the conservation of individual species

• G. L. Simpson’s modes of evolution• Evolution of body size: data• Evolution of body size: models• The concept of quantum evolution• The concept illustrated with African birds• A new criterion for the conservation

Criteria for conservation

• Threatened status• Ecological importance (e.g., keystone species)• Useful to humans• Charisma (e.g., flagship species)• Uniqueness (e.g., aardvark)

Simpson’s two evolutionary modes: phyletic evolution and quantum evolution

Simpson 1944

Simpson’s concept of quantum evolution

Simpson 1944

Modern version of quantum evolution

Lande 1976

Uyeda et al. 2011

Uyeda et al. 2011

Uyeda et al. 2011

±65% change in body size

Uyeda et al. 2011

“The Blunderbuss Pattern”

Uyeda et al. 2011

The multiple-burst model: a process that produces quantum evolution

(peak movement, evolution of the lineage mean)

Uyeda et al. 2011

A single lineage

Time (generations)

Line

age

mea

n

Burst timing distribution (mean time between

bursts = 25 my)

White noise distribution

(dashed)

Burst sizedistribution

(solid)Probability

Prob

abili

ty

Div

erge

nce

B

C

A

Interval (years)

The model that best fits the datahas two modes: phyletic & quantum

Uyeda et al. 2011

Can we detect quantum evolution in the birds of Central Africa?

Provisos• Phylogeny ignored• Exclusive focus on body size• Measure of body size includes tail• Focus on Central Africa ignores

relatives elsewhere

No quantum evolution

Quantum evolution of Great Blue Turaco

Quantum evolution of ground hornbills

Quantum evolution of the Giant Kingfisher

Criteria for conservation

• Threatened status• Ecological importance (e.g., keystone species)• Useful to humans• Charisma (e.g., flagship species)• Uniqueness (e.g., aardvark)• Replacement time (e.g., 25 million years ≧

for a ground hornbill)

Conclusions

• To account for evolutionary pattern in a large data set we need a model with two modes: phyletic and quantum.

• Quantum evolutionary events can lead to rapid, substantial evolution but they are rare, with an average waiting time of 25 million years.

• Some families of birds in Central Africa appear to have experienced quantum evolution (e.g., hornbills, kingfishers, and turacos).

References

Simpson, G. L. 1944. Tempo and Mode in Evolution. Columbia Univ. Press.

Simpson, G. L. 1954. The Major Features of Evolution. Columbia Univ. Press.

Lande, R. 1976.Uyeda, J., T. Hansen, S. J. Arnold, J. Pienaar. 2011. The million-year

wait for evolutionary bursts. Proceedings of the National Academy of Science. U.S.A.

Arnold, S. J. 2014. Phenotypic evolution, the ongoing synthesis. American Naturlist

Van Perlo, Ber. 2002. Birds of Western and Central Africa. Princeton Univ. Press.

AcknowledgementsPhD advisor: Arnold Kluge

Research collaborators: Suzanne Estes, Josef Uyeda, Thomas Hansen, Jason Pienaar

Data: Phil Gingerich, Andrew Hendry, Michael Kinnison NSF OPUS program: Mark Courtney