Evidence for the adaptive significance of circadian rhythms

Shai Yerushalmi, Rachel M. Green

Research output: Contribution to journalArticlepeer-review

222 Scopus citations


Circadian (∼24 h) clock regulated biological rhythms have been identified in a wide range of organisms from prokaryotic unicellular cyanobacteria to higher mammals. These rhythms regulate an enormous variety of processes including gene expression, metabolic processes, activity and reproduction. Given the widespread occurrence of circadian systems it is not surprising that extensive efforts have been directed at understanding the adaptive significance of circadian rhythms. In this review we discuss the approaches and findings that have resulted. In studies on organisms in their natural environments, some species show adaptations in their circadian systems that correlate with living at different latitudes, such as clines in circadian clock properties. Additionally, some species show plasticity in their circadian systems suggested to match the demands of their physical and social environment. A number of experiments, both in the field and in the laboratory, have examined the effects of having a circadian system that does not resonate with the organism's environment. We conclude that the results of these studies suggest that having a circadian system that matches the oscillating environment is adaptive.

Original languageAmerican English
Pages (from-to)970-981
Number of pages12
JournalEcology Letters
Issue number9
StatePublished - Sep 2009


  • Adaptation
  • Circadian
  • Fitness
  • Phenotype
  • Physical environment
  • Plasticity
  • Rhythms
  • Social environment


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