BIOL3045 Lecture Notes - Lecture 9: Beneficial Acclimation Hypothesis, Rainbow Trout, Reaction Norm
3 Jul 2018
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Animal Ecological Physiology BIOL3045 460381099
Lecture 9: Reversible acclimation.
• Acclimation is compensation for environmental change. It is a reversible phenotypic response.
• Thermal reaction norm shifts within individuals to compensate for the new environmental
effect.
• Horizontal shift of reaction norm indicates an interaction between acclimation and acute
conditions. While, vertical shift in reaction norm shows a main effect of acclimation.
• Example: Rainbow trout have a vertical shift in reaction norm during winter to compensate for
negative thermodynamic effect in colder weather. This allows the enzyme activity to remain
optimal, showing a main effect of acclimation.
• Example: Swimming performance in the saltwater crocodile shows a horizontal shift in reaction
norm. This shows complete compensation for the change in environment, suggesting an
interaction between swimming ability and temperature.
Beneficial acclimation hypothesis
• Acclimation is only beneficial when it increases the fitness of an individual.
• Example: Striped marsh frogs show that males acclimate to cold temperatures to enable
efficient use of their calling muscle. This allows them to find females, increasing their chance of
mating, and shows that there is a benefit reproductively. Females have this muscle, but don’t
acclimate as they don’t need its function for reproduction.
Falsification of thermal specialization paradigm
• Predication that animals undergo adaptation in stable environments and acclimation in unstable
environments. This isn’t true as thermal specialists in stable conditions have been known to
acclimate.
• Example: Antarctic fish are known to survive in extreme but stable environments. They have
been found to have perfect swimming acclimation in warmer temperatures, even though it
becomes costly to swim at these higher temperatures.
Read: Beaman, White and Seebacher. 2016. Evolution of plasticity: development and reversible
acclimation. Trends in ecology and evolution, 31, 237-249.
• According to established theory, which conditions should favour the evolution of developmental
plasticity? Developmental plasticity should evolve when environments change across
generations and parental conditions predict offspring conditions.
• What about acclimation? Acclimation should evolve when environments fluctuate within
generations, and parental conditions would be poor predictors of offspring conditions.
• How can acclimation reduce the cost of developmental plasticity? The greatest cost of
developmental plasticity is an environmental mismatch between parent and offspring.
Acclimation by offspring could shift performance curves to compensate at least partially for this
mismatch.
• What is the consequence of a link between developmental plasticity and acclimation? Greater
responsiveness of populations to environmental fluctuations. Can explain evolution of plasticity
under more realistic environmental fluctuations.
Document Summary
Lecture 9: reversible acclimation: acclimation is compensation for environmental change. It is a reversible phenotypic response: thermal reaction norm shifts within individuals to compensate for the new environmental effect, horizontal shift of reaction norm indicates an interaction between acclimation and acute conditions. While, vertical shift in reaction norm shows a main effect of acclimation: example: rainbow trout have a vertical shift in reaction norm during winter to compensate for negative thermodynamic effect in colder weather. This allows the enzyme activity to remain optimal, showing a main effect of acclimation: example: swimming performance in the saltwater crocodile shows a horizontal shift in reaction norm. This shows complete compensation for the change in environment, suggesting an interaction between swimming ability and temperature. Beneficial acclimation hypothesis: acclimation is only beneficial when it increases the fitness of an individual, example: striped marsh frogs show that males acclimate to cold temperatures to enable efficient use of their calling muscle.
