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Genetic analyses of a seasonal interval timer
Brian J Prendergast1, Randall A Renstrom, Randy J Nelson
1Department of Psychology, University of Chicago, Chicago, IL 60637, USA. prendergast@uchicago.edu
Journal of Biological Rhythms
|July 13, 2004
Summary
Seasonal clocks, like interval timers, show significant heritability in Siberian hamsters. These findings suggest genetic variation in timing mechanisms allows adaptation to environmental changes.
Area of Science:
- Chronobiology
- Animal Behavior
- Genetics
Background:
- Seasonal clocks enable organisms to anticipate environmental changes, influencing reproduction, metabolism, and behavior.
- Heritable genetic variance in the temporal properties of these clocks is crucial for adaptation but remains largely unexamined.
Purpose of the Study:
- To quantify the intraspecific variance and heritability of the photorefractoriness interval timer in Siberian hamsters.
- To investigate the genetic basis of seasonal clock timing mechanisms.
Main Methods:
- Siberian hamsters were exposed to continuous darkness (DD) to measure the duration of their photorefractoriness interval timer.
- Body weight changes were monitored weekly to determine individual timer responsiveness.
- Intraclass correlation and parent-offspring regression analyses were used to estimate heritability.
Main Results:
- The interval timer duration varied between sexes, being longer and more variable in females than males.
- Significant family resemblance in interval timer duration was observed (intraclass correlation of 0.71).
- Heritability estimates indicated strong additive genetic components, particularly in females (h² = 0.91).
Conclusions:
- Individual differences in seasonal interval timers have a strong heritable basis, primarily in females.
- This genetic variation provides a substrate for natural selection to rapidly shape seasonal clocks.
- Balancing selection may maintain genetic variance, allowing interval timers to be tuned to local environmental conditions.