Adaptive Radiation

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•  Changes in beaks of finches on Daphne Major 

Adaptive radiation describes the rapid evolutionary diversification of a single ancestral line

  • It occurs when members of a single species occupy a variety of distinct niches with different environmental conditions
  • Consequently, members evolve different morphological features (adaptations) in response to the different selection pressures

An example of adaptive radiation can be seen in the variety of beak types seen in the finches of the Galapagos Islands

  • These finches have specialised beak shapes depending on their primary source of nutrition (e.g. seeds, insects, nuts, nectar)

Adaptive Radiation (Darwin’s Finches)

adaptive radiation

Daphne Major

Daphne Major is a volcanic island that forms part of the archipelago that is collectively referred to as the Galapagos Islands

  • It is the native habitat of a variety of bird species known as Darwin’s finches (subfamily: Geospizinae)

Darwin’s finches demonstrate adaptive radiation and show marked variation in beak size and shape according to diet

  • Finches that feed on seeds possess compact, powerful beaks – with larger beaks better equipped to crack larger seed cases

In 1977, an extended drought changed the frequency of larger beak sizes within the population by natural selection

  • Dry conditions result in plants producing larger seeds with tougher seed casings
  • Between 1976 and 1978 there was a change in average beak depth within the finch population
  • Finches with larger beaks were better equipped to feed on the seeds and thus produced more offspring with larger beaks

Natural Selection on Daphne Major

darwins finches