The evolution of beak size and shape in Darwin’s Finches

The role of Developmental Genes and Environmental Conditions

Lindsey WilliamsElisabet Minter

Corita Fields

Smithsonian: Osteology Hall

Smithsonian: Osteology Hall

Examples of

Beak Morphology

Smithsonian: Osteology Hall

Beak Components

Frontonasal massMaxillary prominences

Lateral nasal prominences

Mandibular prominences

Beak Morphology

• Beak length, width, and depth– Environmental

• Parental Diet• Food Availability

– Developmental Genes• BMP4 and Calmodulin

• Parental Diet• Food Availability– Small beaked finches prefer small seeds– Large beaked finches prefer large seeds but have

the ability to consume small seeds

Environmental Influence

Environmental Influence

• During drought of 1977– soft seeds less abundant– Tribulus seeds more abundant• Large, difficult to open

• Larger beaked finches were more fit than their smaller beaked counterparts

• Larger beaks survived due to their ability to open Tribulus seeds easier.

Genetic Influence

• Bone morphogenic protein 4 (BMP4)

• Calmodulin (CaM)

BMP4 Expression

• Examined BMP4 Expression in distal beak mesenchyme of finches

Figure . A. Beak morphologies. B. Stage 26 BMP4 expression C. Stage 29 BMP4 expression

• Result– Enhanced cell proliferation – larger beaks due to significant increases in width,

and depth

• Conclusion– Darwin’s finches exhibit different beak

morphologies in part due to the expression of BMP4

BMP4 Expression

Calmodulin Expression

• Embryonic Stage – Injected CaM via a RCAS

virus into embryo at stage 24

– Collected specimens at day 10

• Result and Conclusion Figure . A shows the wild type specimen without additional presence of calmodulin. B shows the RCAS:CaM infected specimen.

Calmodulin Expression

• Examined expression and calmodulin in the skull of embryonic finches

• Conclusion

Figure . A. and B. Morphologies from a monophyletic group. C. Skeletal morphological differences. D. CaM expression in distal –ventral domain in the mesenchyme of the upper beak.

BMP4 and CaM Expression

Conclusion and Further Research

• Beak morphology is influenced by both developmental genes and environmental factors, not just one

• Expression of CaM and BMP4 in other anatomical structures in both birds and mammals

• What protein is expressed that increases beak length once CaM is expressed?

Bibliography

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• Abzhanov, Arhat, Meredith Protas, B. Rosemary Grant, Peter R. Grant and Clifford J. Tabin. “Bmp4 and Morphological Variation of Beaks in Darwin's Finches.” Science 305.5689 (2004): 1462-465.

• Freeman, Scott, and Jon C. Herron. Evolutionary Analysis. 4th ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2007. Print

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• Snodgrass, Robert E. "The Relation of the Food to the Size and Shape of the Bill in the Galapagos Genus Geospiza." The Auk 19.4 (1902): 367-81. JSTOR. Web. 19 Apr. 2011. <http://www.jstor.org/stable/4069598 .>.

• Wu, Ping, Ting-Xin Jiang, Sanong Suksaweang, Randall Bruce Widelitz, and Cheng-Ming Chuong. "Molecular Shaping of the Beak." Science 305.5689 (2004): 1465-466.

Questions?