Natural selection on circadian function in a semi-natural environment

Collaborators: Kamiel Spoelstra (Princeton University, Max Planck Institute for Ornithology), Serge Daan (U Groningen), Andrew Loudon (U Manchester), Martin Wikelski (Max Planck Institute for Ornithology).

Accurate knowledge of time of day is assumed to be an important organismal capability that enhances fitness in the periodic environment on earth. Circadian rhythms provide organisms with such temporal information, enabling individuals to precisely time daily activities such as foraging, seeking shelter from predators, and resting. While evolutionary benefits of circadian rhythms have been proposed for a long time, their existence has never been unambiguously demonstrated in a natural setting. This stems both from the historic difficulty to monitor circadian behavior under natural conditions as well as a limited availability of methodologies to alter circadian behavior (e.g., pharmacological manipulations or brain ablations).

We are determining the fitness effects of circadian phenotypes in a vertebrate model in naturalistic setting. House mice (Mus musculus domesticus) that are homo- and heterozygous for a specific mutation in circadian genes are housed together with wild-type conspecifics in outdoor enclosures. Csnk1e (or ‘tau') null mutant mice have shorter period lengths (20 h) in behavioral rhythms under constant laboratory conditions compared to wild-type mice. We use miniature transponder identification recording techniques, combined with intensive life-trapping and genetic phenotyping to compare the behavior, reproductive success and longevity among wild-type, homo- and heterozygous mutant mice.

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