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Biology (HMC)

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Hypothesis: Phenotypic variation in traits induced by different incubation temperatures does not persist into the lifetime of young lizards, and therefore contributes little to variation in long-term fitness.

Organism: Western fence lizard (Sceloporus occidentalis).

Methods: Split-clutch laboratory incubation experiment including eggs from two different populations under two different incubation regimes, measurement of morphological traits at hatching, and tracking of morphology and temperature preference behaviour for 7 weeks after hatching.

Results: Several morphological traits, including body mass, hindlimb length, inter-limb length, and tail length, initially differed between the two incubation treatments, but only the difference in tail length persisted to age 7 weeks. Thermal preference was relatively conserved, with juveniles showing no difference in mean selected body temperatures across treatments; however, warm-incubated lizards thermoregulated more precisely than their cool-incubated counterparts.

Conclusion: Studies of incubation effects can reveal changes in animal phenotypes post-hatching, but if these effects do not persist, they may not be subject to natural selection and consequently be of little ecological relevance.


Previously linked to as:,332.

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Publisher: Evolutionary Ecology Research

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© 2007 Stephen C. Adolph

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