Darwin’s finches as an exceptional model of natural selection: not all can survive!

Intense natural selection in a population of Darwin's finches (Geospizinae) in the Galápagos. Boag PT, Grant PR. Science. 1981 Oct 2;214(4516):82-5. doi: 10.1126/science.214.4516.82.

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The theory of evolution by natural selection is the key foundation upon which modern biology is built. Natural selection is the process where organisms that are more suitably adapted to their environment are more likely to survive and reproduce, leading to an increase in that organism’s features in a population. Charles Darwin first introduced this theory in 1859, with considerable backlash due to religion at the time, in his book ‘On the Origin of Species’. A group of finches occupying the Galapagos Islands were studied by Darwin and his colleagues, later being termed the famed ‘Darwin’s Finches’. So, why did these birds become natural selection’s poster child?

The finches developed different characteristics to suit the varying conditions on each of the Galapagos Islands. They appeared so different, Darwin was convinced that they were unrelated at first! These finches are such great models of natural selection that scientists studied them for many years after Darwin. In 1981, Peter Boag and Peter Grant published some intriguing findings. They had studied a population of Darwin’s finches on Daphne Major Island before and after a drought caused a massive reduction in seed abundance. This led to the seeds becoming larger and harder on average, which meant that only larger birds with deeper bills could crack these seeds. Therefore, these birds were more likely to get the food, survive through the drought and reproduce – driving strong natural selection. The type of natural selection was directional natural selection, which occurs when the fitness of an organism increases as the value of a particular trait increases, or vice versa. Tune in to hear the story of these incredible finches, and how Boag and Grant witnessed the most intense directional natural selection for a vertebrate species.

Creator: Erika Lawry

References:
Arbogast BS, Drovetski SV, Curry RL, Boag PT, Seutin G, Grant PR, Grant BR, Anderson DJ. The origin and diversification of Galapagos mockingbirds. Evolution. 2006;60(2):370-382.
Bierema AM, Rudge DW. Using David Lack’s observations of finch beak size to teach natural selection and the nature of science. Am Biol Teach. 2014;76(5): 312-317.

Boag PT, Grant PR. Intense natural selection in a population of Darwin's finches (Geospizinae) in the Galápagos. Science. 1981;214(4516):82-85.
Boero F. From Darwin's Origin of Species toward a theory of natural history. F1000Prime Rep. 2015;7:49.
Grant PR, Grant RB. 40 years of evolution: Darwin's finches on Daphne Major Island. 2014. Princeton University Press, Princeton, USA.
Lack D. Darwin’s finches. 1947. Cambridge University Press, Cambridge, England.
Soons J, Genbrugge A, Podos J, Adriaens D, Aerts P, Dirckx J, Herrel A. Is beak morphology in Darwin's finches tuned to loading demands? PLoS One. 2015;10(6):e0129479.
Tebbich S, Sterelny K, Teschke I. The tale of the finch: adaptive radiation and behavioural flexibility. Philos Trans R Soc Lond B Biol Sci. 2010;365(1543):1099-1109.