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The evolution of beak size and shape in Darwin’s Finches. The role of Developmental Genes and Environmental Conditions. Lindsey Williams Elisabet Minter Corita Fields. Smithsonian: Osteology Hall. Smithsonian: Osteology Hall. Smithsonian: Osteology Hall. Examples of Beak Morphology.
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The evolution of beak size and shape in Darwin’s Finches The role of Developmental Genes and Environmental Conditions Lindsey Williams Elisabet Minter Corita Fields
Smithsonian: Osteology Hall Examples of Beak Morphology
Beak Components Frontonasal mass Maxillary prominences Lateral nasal prominences Mandibular prominences
Beak Morphology • Beak length, width, and depth • Environmental • Parental Diet • Food Availability • Developmental Genes • BMP4 and Calmodulin
Environmental Influence • 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 • 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
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
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.
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 • Abbott, Ian, L. K. Abbott, and P. R. Grant. "Seed Selection and Handling Ability of Four Species of Darwin's Finches." The Condor 7.3 (1975): 332-35. • Abzhanov, Arhat, Winston P. Kuo, Christine Hartmann, B. Rosemary Grant, Peter R. Grant, and Clifford J. Tabin. "The Calmodulin Pathway and Evolution of Elongated Beak Morphology in Darwin's Finches." Nature 442.7102 (2006): 563-67. Print. • 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 • Grant, Rosemary B. and Peter R. Grant. “High Survival of Darwin's Finch Hybrids: Effects of Beak Morphology and Diets.” Ecology 77. 2 (1996): 500-509. • Herrel, A., J. Podos, S. K. Huber, and A. P. Hendry. "Bite Performance and Morphology in a Population of Darwin's Finches: Implications for the Evolution of Beak Shape." Functional Ecology 19.1 (2005): 43-48. • 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.
