Английская Википедия:Brett's hypothesis

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Brett's hypothesis[1][2] also known as the heat-invariant hypothesis[3][4] or Brett's heat-invariant hypothesis[5] proposes that upper thermal tolerance limits are less variable geographically than lower thermal tolerance limits. This hypothesis was originally proposed for fish[1] but lately has been supported by studies with reptiles,[6] amphibians,[5] and aquatic insects.[7] Three different mechanisms are proposed for the existence of this large-scale pattern of thermal tolerance limits variation:

  • A constrained evolutionary potential of upper thermal tolerance limits
  • The buffering effects of thermoregulatory behaviour has greater potential to face heat rather than cold stress
  • Resolution of thermal data used

Global versus local scales in Brett's hypothesis

While Brett's hypothesis has been strongly supported at global scales, heat tolerance seems to respond differently to smaller-scale climatic and habitat factors. For instance, lizards from the Iberian Peninsula[8] show higher variation in upper thermal tolerance limits than in lower thermal tolerance limits. Similar results are found in adult frogs,[5] tadpoles, and dragonfly larvae[7] at local scales.

References

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