Physiological variation and phenotypic plasticity: a response to 'Plasticity in arthropod cryotypes' by Hawes and Bale.

In a recent publication, Hawes and Bale provide an extended discussion of phenotypic plasticity in the context of low temperature responses of animals. They argue that phenotypic plasticity may be partitioned phylogenetically at several levels and go on to explore these levels, and cold hardiness strategies that they term cryotypes, which in their view constitute cryotypic plasticity. Here we argue that this attempt to partition plasticity is misleading, that the term 'genotypic plasticity' is potentially highly confusing and a misnomer for physiological variance, and that the term 'superplasticity' should not be used. We also show that a definition of strategies as cryotypes is not useful and that the hypothesis about the relationship between evolutionary derivation and extent of plasticity in freeze-avoiding vs freeze-tolerant species is not supported by current evidence.